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| <title>Writing Programs with NCURSES</title> |
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| <body> |
| <h1>Writing Programs with NCURSES</h1> |
| |
| <blockquote> |
| by Eric S. Raymond and Zeyd M. Ben-Halim<br> |
| updates since release 1.9.9e by Thomas Dickey |
| </blockquote> |
| |
| <h1>Contents</h1> |
| |
| <ul> |
| <li> |
| <a href="#introduction">Introduction</a> |
| |
| <ul> |
| <li><a href="#history">A Brief History of Curses</a></li> |
| |
| <li><a href="#scope">Scope of This Document</a></li> |
| |
| <li><a href="#terminology">Terminology</a></li> |
| </ul> |
| </li> |
| |
| <li> |
| <a href="#curses">The Curses Library</a> |
| |
| <ul> |
| <li> |
| <a href="#overview">An Overview of Curses</a> |
| |
| <ul> |
| <li><a href="#compiling">Compiling Programs using |
| Curses</a></li> |
| |
| <li><a href="#updating">Updating the Screen</a></li> |
| |
| <li><a href="#stdscr">Standard Windows and Function |
| Naming Conventions</a></li> |
| |
| <li><a href="#variables">Variables</a></li> |
| </ul> |
| </li> |
| |
| <li> |
| <a href="#using">Using the Library</a> |
| |
| <ul> |
| <li><a href="#starting">Starting up</a></li> |
| |
| <li><a href="#output">Output</a></li> |
| |
| <li><a href="#input">Input</a></li> |
| |
| <li><a href="#formschars">Using Forms Characters</a></li> |
| |
| <li><a href="#attributes">Character Attributes and |
| Color</a></li> |
| |
| <li><a href="#mouse">Mouse Interfacing</a></li> |
| |
| <li><a href="#finishing">Finishing Up</a></li> |
| </ul> |
| </li> |
| |
| <li> |
| <a href="#functions">Function Descriptions</a> |
| |
| <ul> |
| <li><a href="#init">Initialization and Wrapup</a></li> |
| |
| <li><a href="#flush">Causing Output to the Terminal</a></li> |
| |
| <li><a href="#lowlevel">Low-Level Capability Access</a></li> |
| |
| <li><a href="#debugging">Debugging</a></li> |
| </ul> |
| </li> |
| |
| <li> |
| <a href="#hints">Hints, Tips, and Tricks</a> |
| |
| <ul> |
| <li><a href="#caution">Some Notes of Caution</a></li> |
| |
| <li><a href="#leaving">Temporarily Leaving ncurses |
| Mode</a></li> |
| |
| <li><a href="#xterm">Using <code>ncurses</code> under |
| <code>xterm</code></a></li> |
| |
| <li><a href="#screens">Handling Multiple Terminal |
| Screens</a></li> |
| |
| <li><a href="#testing">Testing for Terminal |
| Capabilities</a></li> |
| |
| <li><a href="#tuning">Tuning for Speed</a></li> |
| |
| <li><a href="#special">Special Features of |
| <code>ncurses</code></a></li> |
| </ul> |
| </li> |
| |
| <li> |
| <a href="#compat">Compatibility with Older Versions</a> |
| |
| <ul> |
| <li><a href="#refbug">Refresh of Overlapping |
| Windows</a></li> |
| |
| <li><a href="#backbug">Background Erase</a></li> |
| </ul> |
| </li> |
| |
| <li><a href="#xsifuncs">XSI Curses Conformance</a></li> |
| </ul> |
| </li> |
| |
| <li> |
| <a href="#panels">The Panels Library</a> |
| |
| <ul> |
| <li><a href="#pcompile">Compiling With the Panels |
| Library</a></li> |
| |
| <li><a href="#poverview">Overview of Panels</a></li> |
| |
| <li><a href="#pstdscr">Panels, Input, and the Standard |
| Screen</a></li> |
| |
| <li><a href="#hiding">Hiding Panels</a></li> |
| |
| <li><a href="#pmisc">Miscellaneous Other Facilities</a></li> |
| </ul> |
| </li> |
| |
| <li> |
| <a href="#menu">The Menu Library</a> |
| |
| <ul> |
| <li><a href="#mcompile">Compiling with the menu Library</a></li> |
| |
| <li><a href="#moverview">Overview of Menus</a></li> |
| |
| <li><a href="#mselect">Selecting items</a></li> |
| |
| <li><a href="#mdisplay">Menu Display</a></li> |
| |
| <li><a href="#mwindows">Menu Windows</a></li> |
| |
| <li><a href="#minput">Processing Menu Input</a></li> |
| |
| <li><a href="#mmisc">Miscellaneous Other Features</a></li> |
| </ul> |
| </li> |
| |
| <li> |
| <a href="#form">The Forms Library</a> |
| |
| <ul> |
| <li><a href="#fcompile">Compiling with the forms |
| Library</a></li> |
| |
| <li><a href="#foverview">Overview of Forms</a></li> |
| |
| <li><a href="#fcreate">Creating and Freeing Fields and |
| Forms</a></li> |
| |
| <li> |
| <a href="#fattributes">Fetching and Changing Field |
| Attributes</a> |
| |
| <ul> |
| <li><a href="#fsizes">Fetching Size and Location |
| Data</a></li> |
| |
| <li><a href="#flocation">Changing the Field |
| Location</a></li> |
| |
| <li><a href="#fjust">The Justification Attribute</a></li> |
| |
| <li><a href="#fdispatts">Field Display Attributes</a></li> |
| |
| <li><a href="#foptions">Field Option Bits</a></li> |
| |
| <li><a href="#fstatus">Field Status</a></li> |
| |
| <li><a href="#fuser">Field User Pointer</a></li> |
| </ul> |
| </li> |
| |
| <li><a href="#fdynamic">Variable-Sized Fields</a></li> |
| |
| <li> |
| <a href="#fvalidation">Field Validation</a> |
| |
| <ul> |
| <li><a href="#ftype_alpha">TYPE_ALPHA</a></li> |
| |
| <li><a href="#ftype_alnum">TYPE_ALNUM</a></li> |
| |
| <li><a href="#ftype_enum">TYPE_ENUM</a></li> |
| |
| <li><a href="#ftype_integer">TYPE_INTEGER</a></li> |
| |
| <li><a href="#ftype_numeric">TYPE_NUMERIC</a></li> |
| |
| <li><a href="#ftype_regexp">TYPE_REGEXP</a></li> |
| </ul> |
| </li> |
| |
| <li><a href="#fbuffer">Direct Field Buffer Manipulation</a></li> |
| |
| <li><a href="#formattrs">Attributes of Forms</a></li> |
| |
| <li><a href="#fdisplay">Control of Form Display</a></li> |
| |
| <li> |
| <a href="#fdriver">Input Processing in the Forms |
| Driver</a> |
| |
| <ul> |
| <li><a href="#fpage">Page Navigation Requests</a></li> |
| |
| <li><a href="#ffield">Inter-Field Navigation |
| Requests</a></li> |
| |
| <li><a href="#fifield">Intra-Field Navigation |
| Requests</a></li> |
| |
| <li><a href="#fscroll">Scrolling Requests</a></li> |
| |
| <li><a href="#fedit">Field Editing Requests</a></li> |
| |
| <li><a href="#forder">Order Requests</a></li> |
| |
| <li><a href="#fappcmds">Application Commands</a></li> |
| </ul> |
| </li> |
| |
| <li><a href="#fhooks">Field Change Hooks</a></li> |
| |
| <li><a href="#ffocus">Field Change Commands</a></li> |
| |
| <li><a href="#frmoptions">Form Options</a></li> |
| |
| <li> |
| <a href="#fcustom">Custom Validation Types</a> |
| |
| <ul> |
| <li><a href="#flinktypes">Union Types</a></li> |
| |
| <li><a href="#fnewtypes">New Field Types</a></li> |
| |
| <li><a href="#fcheckargs">Validation Function |
| Arguments</a></li> |
| |
| <li><a href="#fcustorder">Order Functions For Custom |
| Types</a></li> |
| |
| <li><a href="#fcustprobs">Avoiding Problems</a></li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| |
| <hr> |
| |
| <h1><a name="introduction" id="introduction">Introduction</a></h1> |
| |
| <p>This document is an introduction to programming with |
| <code>curses</code>. It is not an exhaustive reference for the |
| curses Application Programming Interface (API); that role is |
| filled by the <code>curses</code> manual pages. Rather, it is |
| intended to help C programmers ease into using the package.</p> |
| |
| <p>This document is aimed at C applications programmers not yet |
| specifically familiar with ncurses. If you are already an |
| experienced <code>curses</code> programmer, you should |
| nevertheless read the sections on <a href="#mouse">Mouse |
| Interfacing</a>, <a href="#debugging">Debugging</a>, <a href= |
| "#compat">Compatibility with Older Versions</a>, and <a href= |
| "#hints">Hints, Tips, and Tricks</a>. These will bring you up to |
| speed on the special features and quirks of the |
| <code>ncurses</code> implementation. If you are not so |
| experienced, keep reading.</p> |
| |
| <p>The <code>curses</code> package is a subroutine library for |
| terminal-independent screen-painting and input-event handling |
| which presents a high level screen model to the programmer, |
| hiding differences between terminal types and doing automatic |
| optimization of output to change one screen full of text into |
| another. <code>Curses</code> uses terminfo, which is a database |
| format that can describe the capabilities of thousands of |
| different terminals.</p> |
| |
| <p>The <code>curses</code> API may seem something of an archaism |
| on UNIX desktops increasingly dominated by X, Motif, and Tcl/Tk. |
| Nevertheless, UNIX still supports tty lines and X supports |
| <em>xterm(1)</em>; the <code>curses</code> API has the advantage |
| of (a) back-portability to character-cell terminals, and (b) |
| simplicity. For an application that does not require bit-mapped |
| graphics and multiple fonts, an interface implementation using |
| <code>curses</code> will typically be a great deal simpler and |
| less expensive than one using an X toolkit.</p> |
| |
| <h2><a name="history" id="history">A Brief History of Curses</a></h2> |
| |
| <p>Historically, the first ancestor of <code>curses</code> was |
| the routines written to provide screen-handling for the |
| <code>vi</code> editor; these used the <code>termcap</code> |
| database facility (both released in 3BSD) for describing terminal |
| capabilities. These routines were abstracted into a documented |
| library and first released with the early BSD UNIX versions. All |
| of this work was done by students at the University of California |
| (Berkeley campus). The curses library was first published in |
| 4.0BSD, a year after 3BSD (i.e., late 1980).</p> |
| |
| <p>After graduation, one of those students went to work at |
| AT&T Bell Labs, and made an improved <code>termcap</code> |
| library called <code>terminfo</code> (i.e., |
| “libterm”), and adapted the curses library to use |
| this. That was subsequently released in System V Release 2 (early |
| 1984). Thereafter, other developers added to the curses and |
| terminfo libraries. For instance, a student at Cornell University |
| wrote an improved terminfo library as well as a tool |
| (<code>tic</code>) to compile the terminal descriptions. As a |
| general rule, AT&T did not identify the developers in the |
| source-code or documentation; the <code>tic</code> and |
| <code>infocmp</code> programs are the exceptions.</p> |
| |
| <p>System V Release 3 (System III UNIX) from Bell Labs featured a |
| rewritten and much-improved <code>curses</code> library, along |
| with the <code>tic</code> program (late 1986).</p> |
| |
| <p>To recap, terminfo is based on Berkeley's termcap database, |
| but contains a number of improvements and extensions. |
| Parameterized capabilities strings were introduced, making it |
| possible to describe multiple video attributes, and colors and to |
| handle far more unusual terminals than possible with termcap. In |
| the later AT&T System V releases, <code>curses</code> evolved |
| to use more facilities and offer more capabilities, going far |
| beyond BSD curses in power and flexibility.</p> |
| |
| <h2><a name="scope" id="scope">Scope of This Document</a></h2> |
| |
| <p>This document describes <code>ncurses</code>, a free |
| implementation of the System V <code>curses</code> API with some |
| clearly marked extensions. It includes the following System V |
| curses features:</p> |
| |
| <ul> |
| <li>Support for multiple screen highlights (BSD curses could |
| only handle one “standout” highlight, usually |
| reverse-video).</li> |
| |
| <li>Support for line- and box-drawing using forms |
| characters.</li> |
| |
| <li>Recognition of function keys on input.</li> |
| |
| <li>Color support.</li> |
| |
| <li>Support for pads (windows of larger than screen size on |
| which the screen or a subwindow defines a viewport).</li> |
| </ul> |
| |
| <p>Also, this package makes use of the insert and delete line and |
| character features of terminals so equipped, and determines how |
| to optimally use these features with no help from the programmer. |
| It allows arbitrary combinations of video attributes to be |
| displayed, even on terminals that leave “magic |
| cookies” on the screen to mark changes in attributes.</p> |
| |
| <p>The <code>ncurses</code> package can also capture and use |
| event reports from a mouse in some environments (notably, xterm |
| under the X window system). This document includes tips for using |
| the mouse.</p> |
| |
| <p>The <code>ncurses</code> package was originated by Pavel |
| Curtis. The original maintainer of this package is <a href= |
| "mailto:zmbenhal@netcom.com">Zeyd Ben-Halim</a> |
| <zmbenhal@netcom.com>. <a href= |
| "mailto:esr@snark.thyrsus.com">Eric S. Raymond</a> |
| <esr@snark.thyrsus.com> wrote many of the new features in |
| versions after 1.8.1 and wrote most of this introduction. |
| Jürgen Pfeifer wrote all of the menu and forms code as well |
| as the <a href="http://www.adahome.com">Ada95</a> binding. |
| Ongoing work is being done by <a href= |
| "mailto:dickey@invisible-island.net">Thomas Dickey</a> |
| (maintainer). Contact the current maintainers at <a href= |
| "mailto:bug-ncurses@gnu.org">bug-ncurses@gnu.org</a>.</p> |
| |
| <p>This document also describes the <a href="#panels">panels</a> |
| extension library, similarly modeled on the SVr4 panels facility. |
| This library allows you to associate backing store with each of a |
| stack or deck of overlapping windows, and provides operations for |
| moving windows around in the stack that change their visibility |
| in the natural way (handling window overlaps).</p> |
| |
| <p>Finally, this document describes in detail the <a href= |
| "#menu">menus</a> and <a href="#form">forms</a> extension |
| libraries, also cloned from System V, which support easy |
| construction and sequences of menus and fill-in forms.</p> |
| |
| <h2><a name="terminology" id="terminology">Terminology</a></h2> |
| |
| <p>In this document, the following terminology is used with |
| reasonable consistency:</p> |
| |
| <dl> |
| <dt>window</dt> |
| |
| <dd>A data structure describing a sub-rectangle of the screen |
| (possibly the entire screen). You can write to a window as |
| though it were a miniature screen, scrolling independently of |
| other windows on the physical screen.</dd> |
| |
| <dt>screens</dt> |
| |
| <dd>A subset of windows which are as large as the terminal |
| screen, i.e., they start at the upper left hand corner and |
| encompass the lower right hand corner. One of these, |
| <code>stdscr</code>, is automatically provided for the |
| programmer.</dd> |
| |
| <dt>terminal screen</dt> |
| |
| <dd>The package's idea of what the terminal display currently |
| looks like, i.e., what the user sees now. This is a special |
| screen.</dd> |
| </dl> |
| |
| <h1><a name="curses" id="curses">The Curses Library</a></h1> |
| |
| <h2><a name="overview" id="overview">An Overview of Curses</a></h2> |
| |
| <h3><a name="compiling" id="compiling">Compiling Programs using |
| Curses</a></h3> |
| |
| <p>In order to use the library, it is necessary to have certain |
| types and variables defined. Therefore, the programmer must have |
| a line:</p> |
| |
| <pre> |
| #include <curses.h> |
| </pre> |
| |
| <p>at the top of the program source. The screen package uses the |
| Standard I/O library, so <code><curses.h></code> includes |
| <code><stdio.h></code>. <code><curses.h></code> also |
| includes <code><termios.h></code>, |
| <code><termio.h></code>, or <code><sgtty.h></code> |
| depending on your system. It is redundant (but harmless) for the |
| programmer to do these includes, too. In linking with |
| <code>curses</code> you need to have <code>-lncurses</code> in |
| your LDFLAGS or on the command line. There is no need for any |
| other libraries.</p> |
| |
| <h3><a name="updating" id="updating">Updating the Screen</a></h3> |
| |
| <p>In order to update the screen optimally, it is necessary for |
| the routines to know what the screen currently looks like and |
| what the programmer wants it to look like next. For this purpose, |
| a data type (structure) named WINDOW is defined which describes a |
| window image to the routines, including its starting position on |
| the screen (the (y, x) coordinates of the upper left hand corner) |
| and its size. One of these (called <code>curscr</code>, for |
| current screen) is a screen image of what the terminal currently |
| looks like. Another screen (called <code>stdscr</code>, for |
| standard screen) is provided by default to make changes on.</p> |
| |
| <p>A window is a purely internal representation. It is used to |
| build and store a potential image of a portion of the terminal. |
| It does not bear any necessary relation to what is really on the |
| terminal screen; it is more like a scratchpad or write |
| buffer.</p> |
| |
| <p>To make the section of physical screen corresponding to a |
| window reflect the contents of the window structure, the routine |
| <code>refresh()</code> (or <code>wrefresh()</code> if the window |
| is not <code>stdscr</code>) is called.</p> |
| |
| <p>A given physical screen section may be within the scope of any |
| number of overlapping windows. Also, changes can be made to |
| windows in any order, without regard to motion efficiency. Then, |
| at will, the programmer can effectively say “make it look |
| like this,” and let the package implementation determine |
| the most efficient way to repaint the screen.</p> |
| |
| <h3><a name="stdscr" id="stdscr">Standard Windows and Function |
| Naming Conventions</a></h3> |
| |
| <p>As hinted above, the routines can use several windows, but two |
| are automatically given: <code>curscr</code>, which knows what |
| the terminal looks like, and <code>stdscr</code>, which is what |
| the programmer wants the terminal to look like next. The user |
| should never actually access <code>curscr</code> directly. |
| Changes should be made to through the API, and then the routine |
| <code>refresh()</code> (or <code>wrefresh()</code>) called.</p> |
| |
| <p>Many functions are defined to use <code>stdscr</code> as a |
| default screen. For example, to add a character to |
| <code>stdscr</code>, one calls <code>addch()</code> with the |
| desired character as argument. To write to a different window. |
| use the routine <code>waddch()</code> (for |
| <strong>w</strong>indow-specific addch()) is provided. This |
| convention of prepending function names with a “w” |
| when they are to be applied to specific windows is consistent. |
| The only routines which do not follow it are those for which a |
| window must always be specified.</p> |
| |
| <p>In order to move the current (y, x) coordinates from one point |
| to another, the routines <code>move()</code> and |
| <code>wmove()</code> are provided. However, it is often desirable |
| to first move and then perform some I/O operation. In order to |
| avoid clumsiness, most I/O routines can be preceded by the prefix |
| “mv” and the desired (y, x) coordinates prepended to |
| the arguments to the function. For example, the calls</p> |
| |
| <pre> |
| move(y, x); |
| addch(ch); |
| </pre> |
| |
| <p>can be replaced by</p> |
| |
| <pre> |
| mvaddch(y, x, ch); |
| </pre> |
| |
| <p>and</p> |
| |
| <pre> |
| wmove(win, y, x); |
| waddch(win, ch); |
| </pre> |
| |
| <p>can be replaced by</p> |
| |
| <pre> |
| mvwaddch(win, y, x, ch); |
| </pre> |
| |
| <p>Note that the window description pointer (win) comes before |
| the added (y, x) coordinates. If a function requires a window |
| pointer, it is always the first parameter passed.</p> |
| |
| <h3><a name="variables" id="variables">Variables</a></h3> |
| |
| <p>The <code>curses</code> library sets some variables describing |
| the terminal capabilities.</p> |
| |
| <pre> |
| type name description |
| ------------------------------------------------------------------ |
| int LINES number of lines on the terminal |
| int COLS number of columns on the terminal |
| </pre> |
| |
| <p>The <code>curses.h</code> also introduces some |
| <code>#define</code> constants and types of general |
| usefulness:</p> |
| |
| <dl> |
| <dt><code>bool</code> |
| </dt> |
| |
| <dd>boolean type, actually a “char” (e.g., |
| <code>bool doneit;</code>)</dd> |
| |
| <dt><code>TRUE</code> |
| </dt> |
| |
| <dd>boolean “true” flag (1).</dd> |
| |
| <dt><code>FALSE</code> |
| </dt> |
| |
| <dd>boolean “false” flag (0).</dd> |
| |
| <dt><code>ERR</code> |
| </dt> |
| |
| <dd>error flag returned by routines on a failure (-1).</dd> |
| |
| <dt><code>OK</code> |
| </dt> |
| |
| <dd>error flag returned by routines when things go right.</dd> |
| </dl> |
| |
| <h2><a name="using" id="using">Using the Library</a></h2> |
| |
| <p>Now we describe how to actually use the screen package. In it, |
| we assume all updating, reading, etc. is applied to |
| <code>stdscr</code>. These instructions will work on any window, |
| providing you change the function names and parameters as |
| mentioned above.</p> |
| |
| <p>Here is a sample program to motivate the discussion:</p> |
| |
| <pre> |
| #include <stdlib.h> |
| #include <curses.h> |
| #include <signal.h> |
| |
| static void finish(int sig); |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| int num = 0; |
| |
| /* initialize your non-curses data structures here */ |
| |
| (void) signal(SIGINT, finish); /* arrange interrupts to terminate */ |
| |
| (void) initscr(); /* initialize the curses library */ |
| keypad(stdscr, TRUE); /* enable keyboard mapping */ |
| (void) nonl(); /* tell curses not to do NL->CR/NL on output */ |
| (void) cbreak(); /* take input chars one at a time, no wait for \n */ |
| (void) echo(); /* echo input - in color */ |
| |
| if (has_colors()) |
| { |
| start_color(); |
| |
| /* |
| * Simple color assignment, often all we need. Color pair 0 cannot |
| * be redefined. This example uses the same value for the color |
| * pair as for the foreground color, though of course that is not |
| * necessary: |
| */ |
| init_pair(1, COLOR_RED, COLOR_BLACK); |
| init_pair(2, COLOR_GREEN, COLOR_BLACK); |
| init_pair(3, COLOR_YELLOW, COLOR_BLACK); |
| init_pair(4, COLOR_BLUE, COLOR_BLACK); |
| init_pair(5, COLOR_CYAN, COLOR_BLACK); |
| init_pair(6, COLOR_MAGENTA, COLOR_BLACK); |
| init_pair(7, COLOR_WHITE, COLOR_BLACK); |
| } |
| |
| for (;;) |
| { |
| int c = getch(); /* refresh, accept single keystroke of input */ |
| attrset(COLOR_PAIR(num % 8)); |
| num++; |
| |
| /* process the command keystroke */ |
| } |
| |
| finish(0); /* we are done */ |
| } |
| |
| static void finish(int sig) |
| { |
| endwin(); |
| |
| /* do your non-curses wrapup here */ |
| |
| exit(0); |
| } |
| </pre> |
| |
| <h3><a name="starting" id="starting">Starting up</a></h3> |
| |
| <p>In order to use the screen package, the routines must know |
| about terminal characteristics, and the space for |
| <code>curscr</code> and <code>stdscr</code> must be allocated. |
| These function <code>initscr()</code> does both these things. |
| Since it must allocate space for the windows, it can overflow |
| memory when attempting to do so. On the rare occasions this |
| happens, <code>initscr()</code> will terminate the program with |
| an error message. <code>initscr()</code> must always be called |
| before any of the routines which affect windows are used. If it |
| is not, the program will core dump as soon as either |
| <code>curscr</code> or <code>stdscr</code> are referenced. |
| However, it is usually best to wait to call it until after you |
| are sure you will need it, like after checking for startup |
| errors. Terminal status changing routines like <code>nl()</code> |
| and <code>cbreak()</code> should be called after |
| <code>initscr()</code>.</p> |
| |
| <p>Once the screen windows have been allocated, you can set them |
| up for your program. If you want to, say, allow a screen to |
| scroll, use <code>scrollok()</code>. If you want the cursor to be |
| left in place after the last change, use <code>leaveok()</code>. |
| If this is not done, <code>refresh()</code> will move the cursor |
| to the window's current (y, x) coordinates after updating it.</p> |
| |
| <p>You can create new windows of your own using the functions |
| <code>newwin()</code>, <code>derwin()</code>, and |
| <code>subwin()</code>. The routine <code>delwin()</code> will |
| allow you to get rid of old windows. All the options described |
| above can be applied to any window.</p> |
| |
| <h3><a name="output" id="output">Output</a></h3> |
| |
| <p>Now that we have set things up, we will want to actually |
| update the terminal. The basic functions used to change what will |
| go on a window are <code>addch()</code> and <code>move()</code>. |
| <code>addch()</code> adds a character at the current (y, x) |
| coordinates. <code>move()</code> changes the current (y, x) |
| coordinates to whatever you want them to be. It returns |
| <code>ERR</code> if you try to move off the window. As mentioned |
| above, you can combine the two into <code>mvaddch()</code> to do |
| both things at once.</p> |
| |
| <p>The other output functions, such as <code>addstr()</code> and |
| <code>printw()</code>, all call <code>addch()</code> to add |
| characters to the window.</p> |
| |
| <p>After you have put on the window what you want there, when you |
| want the portion of the terminal covered by the window to be made |
| to look like it, you must call <code>refresh()</code>. In order |
| to optimize finding changes, <code>refresh()</code> assumes that |
| any part of the window not changed since the last |
| <code>refresh()</code> of that window has not been changed on the |
| terminal, i.e., that you have not refreshed a portion of the |
| terminal with an overlapping window. If this is not the case, the |
| routine <code>touchwin()</code> is provided to make it look like |
| the entire window has been changed, thus making |
| <code>refresh()</code> check the whole subsection of the terminal |
| for changes.</p> |
| |
| <p>If you call <code>wrefresh()</code> with <code>curscr</code> |
| as its argument, it will make the screen look like |
| <code>curscr</code> thinks it looks like. This is useful for |
| implementing a command which would redraw the screen in case it |
| get messed up.</p> |
| |
| <h3><a name="input" id="input">Input</a></h3> |
| |
| <p>The complementary function to <code>addch()</code> is |
| <code>getch()</code> which, if echo is set, will call |
| <code>addch()</code> to echo the character. Since the screen |
| package needs to know what is on the terminal at all times, if |
| characters are to be echoed, the tty must be in raw or cbreak |
| mode. Since initially the terminal has echoing enabled and is in |
| ordinary “cooked” mode, one or the other has to |
| changed before calling <code>getch()</code>; otherwise, the |
| program's output will be unpredictable.</p> |
| |
| <p>When you need to accept line-oriented input in a window, the |
| functions <code>wgetstr()</code> and friends are available. There |
| is even a <code>wscanw()</code> function that can do |
| <code>scanf()</code>(3)-style multi-field parsing on window |
| input. These pseudo-line-oriented functions turn on echoing while |
| they execute.</p> |
| |
| <p>The example code above uses the call <code>keypad(stdscr, |
| TRUE)</code> to enable support for function-key mapping. With |
| this feature, the <code>getch()</code> code watches the input |
| stream for character sequences that correspond to arrow and |
| function keys. These sequences are returned as pseudo-character |
| values. The <code>#define</code> values returned are listed in |
| the <code>curses.h</code> The mapping from sequences to |
| <code>#define</code> values is determined by <code>key_</code> |
| capabilities in the terminal's terminfo entry.</p> |
| |
| <h3><a name="formschars" id="formschars">Using Forms |
| Characters</a></h3> |
| |
| <p>The <code>addch()</code> function (and some others, including |
| <code>box()</code> and <code>border()</code>) can accept some |
| pseudo-character arguments which are specially defined by |
| <code>ncurses</code>. These are <code>#define</code> values set |
| up in the <code>curses.h</code> header; see there for a complete |
| list (look for the prefix <code>ACS_</code>).</p> |
| |
| <p>The most useful of the ACS defines are the forms-drawing |
| characters. You can use these to draw boxes and simple graphs on |
| the screen. If the terminal does not have such characters, |
| <code>curses.h</code> will map them to a recognizable (though |
| ugly) set of ASCII defaults.</p> |
| |
| <h3><a name="attributes" id="attributes">Character Attributes and |
| Color</a></h3> |
| |
| <p>The <code>ncurses</code> package supports screen highlights |
| including standout, reverse-video, underline, and blink. It also |
| supports color, which is treated as another kind of |
| highlight.</p> |
| |
| <p>Highlights are encoded, internally, as high bits of the |
| pseudo-character type (<code>chtype</code>) that |
| <code>curses.h</code> uses to represent the contents of a screen |
| cell. See the <code>curses.h</code> header file for a complete |
| list of highlight mask values (look for the prefix |
| <code>A_</code>).</p> |
| |
| <p>There are two ways to make highlights. One is to logical-or |
| the value of the highlights you want into the character argument |
| of an <code>addch()</code> call, or any other output call that |
| takes a <code>chtype</code> argument.</p> |
| |
| <p>The other is to set the current-highlight value. This is |
| <em>logical-OR</em>ed with any highlight you specify the first |
| way. You do this with the functions <code>attron()</code>, |
| <code>attroff()</code>, and <code>attrset()</code>; see the |
| manual pages for details. Color is a special kind of highlight. |
| The package actually thinks in terms of color pairs, combinations |
| of foreground and background colors. The sample code above sets |
| up eight color pairs, all of the guaranteed-available colors on |
| black. Note that each color pair is, in effect, given the name of |
| its foreground color. Any other range of eight non-conflicting |
| values could have been used as the first arguments of the |
| <code>init_pair()</code> values.</p> |
| |
| <p>Once you have done an <code>init_pair()</code> that creates |
| color-pair N, you can use <code>COLOR_PAIR(N)</code> as a |
| highlight that invokes that particular color combination. Note |
| that <code>COLOR_PAIR(N)</code>, for constant N, is itself a |
| compile-time constant and can be used in initializers.</p> |
| |
| <h3><a name="mouse" id="mouse">Mouse Interfacing</a></h3> |
| |
| <p>The <code>ncurses</code> library also provides a mouse |
| interface.</p> |
| |
| <blockquote> |
| <strong>NOTE:</strong> this facility is specific to |
| <code>ncurses</code>, it is not part of either the XSI Curses |
| standard, nor of System V Release 4, nor BSD curses. System V |
| Release 4 curses contains code with similar interface |
| definitions, however it is not documented. Other than by |
| disassembling the library, we have no way to determine exactly |
| how that mouse code works. Thus, we recommend that you wrap |
| mouse-related code in an #ifdef using the feature macro |
| NCURSES_MOUSE_VERSION so it will not be compiled and linked on |
| non-ncurses systems. |
| </blockquote> |
| |
| <p>Presently, mouse event reporting works in the following |
| environments:</p> |
| |
| <ul> |
| <li>xterm and similar programs such as rxvt.</li> |
| |
| <li>Linux console, when configured with <code>gpm</code>(1), |
| Alessandro Rubini's mouse server.</li> |
| |
| <li>FreeBSD sysmouse (console)</li> |
| |
| <li>OS/2 EMX</li> |
| </ul> |
| |
| <p>The mouse interface is very simple. To activate it, you use |
| the function <code>mousemask()</code>, passing it as first |
| argument a bit-mask that specifies what kinds of events you want |
| your program to be able to see. It will return the bit-mask of |
| events that actually become visible, which may differ from the |
| argument if the mouse device is not capable of reporting some of |
| the event types you specify.</p> |
| |
| <p>Once the mouse is active, your application's command loop |
| should watch for a return value of <code>KEY_MOUSE</code> from |
| <code>wgetch()</code>. When you see this, a mouse event report |
| has been queued. To pick it off the queue, use the function |
| <code>getmouse()</code> (you must do this before the next |
| <code>wgetch()</code>, otherwise another mouse event might come |
| in and make the first one inaccessible).</p> |
| |
| <p>Each call to <code>getmouse()</code> fills a structure (the |
| address of which you will pass it) with mouse event data. The |
| event data includes zero-origin, screen-relative character-cell |
| coordinates of the mouse pointer. It also includes an event mask. |
| Bits in this mask will be set, corresponding to the event type |
| being reported.</p> |
| |
| <p>The mouse structure contains two additional fields which may |
| be significant in the future as ncurses interfaces to new kinds |
| of pointing device. In addition to x and y coordinates, there is |
| a slot for a z coordinate; this might be useful with |
| touch-screens that can return a pressure or duration parameter. |
| There is also a device ID field, which could be used to |
| distinguish between multiple pointing devices.</p> |
| |
| <p>The class of visible events may be changed at any time via |
| <code>mousemask()</code>. Events that can be reported include |
| presses, releases, single-, double- and triple-clicks (you can |
| set the maximum button-down time for clicks). If you do not make |
| clicks visible, they will be reported as press-release pairs. In |
| some environments, the event mask may include bits reporting the |
| state of shift, alt, and ctrl keys on the keyboard during the |
| event.</p> |
| |
| <p>A function to check whether a mouse event fell within a given |
| window is also supplied. You can use this to see whether a given |
| window should consider a mouse event relevant to it.</p> |
| |
| <p>Because mouse event reporting will not be available in all |
| environments, it would be unwise to build <code>ncurses</code> |
| applications that <em>require</em> the use of a mouse. Rather, |
| you should use the mouse as a shortcut for point-and-shoot |
| commands your application would normally accept from the |
| keyboard. Two of the test games in the <code>ncurses</code> |
| distribution (<code>bs</code> and <code>knight</code>) contain |
| code that illustrates how this can be done.</p> |
| |
| <p>See the manual page <code>curs_mouse(3X)</code> for full |
| details of the mouse-interface functions.</p> |
| |
| <h3><a name="finishing" id="finishing">Finishing Up</a></h3> |
| |
| <p>In order to clean up after the <code>ncurses</code> routines, |
| the routine <code>endwin()</code> is provided. It restores tty |
| modes to what they were when <code>initscr()</code> was first |
| called, and moves the cursor down to the lower-left corner. Thus, |
| anytime after the call to initscr, <code>endwin()</code> should |
| be called before exiting.</p> |
| |
| <h2><a name="functions" id="functions">Function Descriptions</a></h2> |
| |
| <p>We describe the detailed behavior of some important curses |
| functions here, as a supplement to the manual page |
| descriptions.</p> |
| |
| <h3><a name="init" id="init">Initialization and Wrapup</a></h3> |
| |
| <dl> |
| <dt><code>initscr()</code> |
| </dt> |
| |
| <dd>The first function called should almost always be |
| <code>initscr()</code>. This will determine the terminal type |
| and initialize curses data structures. <code>initscr()</code> |
| also arranges that the first call to <code>refresh()</code> |
| will clear the screen. If an error occurs a message is written |
| to standard error and the program exits. Otherwise it returns a |
| pointer to stdscr. A few functions may be called before initscr |
| (<code>slk_init()</code>, <code>filter()</code>, |
| <code>ripoffline()</code>, <code>use_env()</code>, and, if you |
| are using multiple terminals, <code>newterm()</code>.)</dd> |
| |
| <dt><code>endwin()</code> |
| </dt> |
| |
| <dd>Your program should always call <code>endwin()</code> |
| before exiting or shelling out of the program. This function |
| will restore tty modes, move the cursor to the lower left |
| corner of the screen, reset the terminal into the proper |
| non-visual mode. Calling <code>refresh()</code> or |
| <code>doupdate()</code> after a temporary escape from the |
| program will restore the ncurses screen from before the |
| escape.</dd> |
| |
| <dt><code>newterm(type, ofp, ifp)</code> |
| </dt> |
| |
| <dd>A program which outputs to more than one terminal should |
| use <code>newterm()</code> instead of <code>initscr()</code>. |
| <code>newterm()</code> should be called once for each terminal. |
| It returns a variable of type <code>SCREEN *</code> which |
| should be saved as a reference to that terminal. (NOTE: a |
| SCREEN variable is not a <em>screen</em> in the sense we are |
| describing in this introduction, but a collection of parameters |
| used to assist in optimizing the display.) The arguments are |
| the type of the terminal (a string) and <code>FILE</code> |
| pointers for the output and input of the terminal. If type is |
| NULL then the environment variable <code>$TERM</code> is used. |
| <code>endwin()</code> should called once at wrapup time for |
| each terminal opened using this function.</dd> |
| |
| <dt><code>set_term(new)</code> |
| </dt> |
| |
| <dd>This function is used to switch to a different terminal |
| previously opened by <code>newterm()</code>. The screen |
| reference for the new terminal is passed as the parameter. The |
| previous terminal is returned by the function. All other calls |
| affect only the current terminal.</dd> |
| |
| <dt><code>delscreen(sp)</code> |
| </dt> |
| |
| <dd>The inverse of <code>newterm()</code>; deallocates the data |
| structures associated with a given <code>SCREEN</code> |
| reference.</dd> |
| </dl> |
| |
| <h3><a name="flush" id="flush">Causing Output to the Terminal</a></h3> |
| |
| <dl> |
| <dt><code>refresh()</code> and <code>wrefresh(win)</code></dt> |
| |
| <dd>These functions must be called to actually get any output |
| on the terminal, as other routines merely manipulate data |
| structures. <code>wrefresh()</code> copies the named window to |
| the physical terminal screen, taking into account what is |
| already there in order to do optimizations. |
| <code>refresh()</code> does a refresh of <code>stdscr</code>. |
| Unless <code>leaveok()</code> has been enabled, the physical |
| cursor of the terminal is left at the location of the window's |
| cursor.</dd> |
| |
| <dt><code>doupdate()</code> and |
| <code>wnoutrefresh(win)</code></dt> |
| |
| <dd>These two functions allow multiple updates with more |
| efficiency than wrefresh. To use them, it is important to |
| understand how curses works. In addition to all the window |
| structures, curses keeps two data structures representing the |
| terminal screen: a physical screen, describing what is actually |
| on the screen, and a virtual screen, describing what the |
| programmer wants to have on the screen. wrefresh works by first |
| copying the named window to the virtual screen |
| (<code>wnoutrefresh()</code>), and then calling the routine to |
| update the screen (<code>doupdate()</code>). If the programmer |
| wishes to output several windows at once, a series of calls to |
| <code>wrefresh</code> will result in alternating calls to |
| <code>wnoutrefresh()</code> and <code>doupdate()</code>, |
| causing several bursts of output to the screen. By calling |
| <code>wnoutrefresh()</code> for each window, it is then |
| possible to call <code>doupdate()</code> once, resulting in |
| only one burst of output, with fewer total characters |
| transmitted (this also avoids a visually annoying flicker at |
| each update).</dd> |
| </dl> |
| |
| <h3><a name="lowlevel" id="lowlevel">Low-Level Capability |
| Access</a></h3> |
| |
| <dl> |
| <dt><code>setupterm(term, filenum, errret)</code> |
| </dt> |
| |
| <dd> |
| This routine is called to initialize a terminal's |
| description, without setting up the curses screen structures |
| or changing the tty-driver mode bits. <code>term</code> is |
| the character string representing the name of the terminal |
| being used. <code>filenum</code> is the UNIX file descriptor |
| of the terminal to be used for output. <code>errret</code> is |
| a pointer to an integer, in which a success or failure |
| indication is returned. The values returned can be 1 (all is |
| well), 0 (no such terminal), or -1 (some problem locating the |
| terminfo database). |
| |
| <p>The value of <code>term</code> can be given as NULL, which |
| will cause the value of <code>TERM</code> in the environment |
| to be used. The <code>errret</code> pointer can also be given |
| as NULL, meaning no error code is wanted. If |
| <code>errret</code> is defaulted, and something goes wrong, |
| <code>setupterm()</code> will print an appropriate error |
| message and exit, rather than returning. Thus, a simple |
| program can call setupterm(0, 1, 0) and not worry about |
| initialization errors.</p> |
| |
| <p>After the call to <code>setupterm()</code>, the global |
| variable <code>cur_term</code> is set to point to the current |
| structure of terminal capabilities. By calling |
| <code>setupterm()</code> for each terminal, and saving and |
| restoring <code>cur_term</code>, it is possible for a program |
| to use two or more terminals at once. |
| <code>Setupterm()</code> also stores the names section of the |
| terminal description in the global character array |
| <code>ttytype[]</code>. Subsequent calls to |
| <code>setupterm()</code> will overwrite this array, so you |
| will have to save it yourself if need be.</p> |
| </dd> |
| </dl> |
| |
| <h3><a name="debugging" id="debugging">Debugging</a></h3> |
| |
| <blockquote> |
| <strong>NOTE:</strong> These functions are not part of the |
| standard curses API! |
| </blockquote> |
| |
| <dl> |
| <dt><code>trace()</code> |
| </dt> |
| |
| <dd>This function can be used to explicitly set a trace level. |
| If the trace level is nonzero, execution of your program will |
| generate a file called “trace” in the current |
| working directory containing a report on the library's actions. |
| Higher trace levels enable more detailed (and verbose) |
| reporting -- see comments attached to <code>TRACE_</code> |
| defines in the <code>curses.h</code> file for details. (It is |
| also possible to set a trace level by assigning a trace level |
| value to the environment variable |
| <code>NCURSES_TRACE</code>).</dd> |
| |
| <dt><code>_tracef()</code> |
| </dt> |
| |
| <dd>This function can be used to output your own debugging |
| information. It is only available only if you link with |
| -lncurses_g. It can be used the same way as |
| <code>printf()</code>, only it outputs a newline after the end |
| of arguments. The output goes to a file called |
| <code>trace</code> in the current directory.</dd> |
| </dl> |
| |
| <p>Trace logs can be difficult to interpret due to the sheer |
| volume of data dumped in them. There is a script called |
| <strong>tracemunch</strong> included with the |
| <code>ncurses</code> distribution that can alleviate this problem |
| somewhat; it compacts long sequences of similar operations into |
| more succinct single-line pseudo-operations. These pseudo-ops can |
| be distinguished by the fact that they are named in capital |
| letters.</p> |
| |
| <h2><a name="hints" id="hints">Hints, Tips, and Tricks</a></h2> |
| |
| <p>The <code>ncurses</code> manual pages are a complete reference |
| for this library. In the remainder of this document, we discuss |
| various useful methods that may not be obvious from the manual |
| page descriptions.</p> |
| |
| <h3><a name="caution" id="caution">Some Notes of Caution</a></h3> |
| |
| <p>If you find yourself thinking you need to use |
| <code>noraw()</code> or <code>nocbreak()</code>, think again and |
| move carefully. It is probably better design to use |
| <code>getstr()</code> or one of its relatives to simulate cooked |
| mode. The <code>noraw()</code> and <code>nocbreak()</code> |
| functions try to restore cooked mode, but they may end up |
| clobbering some control bits set before you started your |
| application. Also, they have always been poorly documented, and |
| are likely to hurt your application's usability with other curses |
| libraries.</p> |
| |
| <p>Bear in mind that <code>refresh()</code> is a synonym for |
| <code>wrefresh(stdscr)</code>. Do not try to mix use of |
| <code>stdscr</code> with use of windows declared by |
| <code>newwin()</code>; a <code>refresh()</code> call will blow |
| them off the screen. The right way to handle this is to use |
| <code>subwin()</code>, or not touch <code>stdscr</code> at all |
| and tile your screen with declared windows which you then |
| <code>wnoutrefresh()</code> somewhere in your program event loop, |
| with a single <code>doupdate()</code> call to trigger actual |
| repainting.</p> |
| |
| <p>You are much less likely to run into problems if you design |
| your screen layouts to use tiled rather than overlapping windows. |
| Historically, curses support for overlapping windows has been |
| weak, fragile, and poorly documented. The <code>ncurses</code> |
| library is not yet an exception to this rule.</p> |
| |
| <p>There is a panels library included in the <code>ncurses</code> |
| distribution that does a pretty good job of strengthening the |
| overlapping-windows facilities.</p> |
| |
| <p>Try to avoid using the global variables LINES and COLS. Use |
| <code>getmaxyx()</code> on the <code>stdscr</code> context |
| instead. Reason: your code may be ported to run in an environment |
| with window resizes, in which case several screens could be open |
| with different sizes.</p> |
| |
| <h3><a name="leaving" id="leaving">Temporarily Leaving NCURSES |
| Mode</a></h3> |
| |
| <p>Sometimes you will want to write a program that spends most of |
| its time in screen mode, but occasionally returns to ordinary |
| “cooked” mode. A common reason for this is to support |
| shell-out. This behavior is simple to arrange in |
| <code>ncurses</code>.</p> |
| |
| <p>To leave <code>ncurses</code> mode, call <code>endwin()</code> |
| as you would if you were intending to terminate the program. This |
| will take the screen back to cooked mode; you can do your |
| shell-out. When you want to return to <code>ncurses</code> mode, |
| simply call <code>refresh()</code> or <code>doupdate()</code>. |
| This will repaint the screen.</p> |
| |
| <p>There is a boolean function, <code>isendwin()</code>, which |
| code can use to test whether <code>ncurses</code> screen mode is |
| active. It returns <code>TRUE</code> in the interval between an |
| <code>endwin()</code> call and the following |
| <code>refresh()</code>, <code>FALSE</code> otherwise.</p> |
| |
| <p>Here is some sample code for shellout:</p> |
| |
| <pre> |
| addstr("Shelling out..."); |
| def_prog_mode(); /* save current tty modes */ |
| endwin(); /* restore original tty modes */ |
| system("sh"); /* run shell */ |
| addstr("returned.\n"); /* prepare return message */ |
| refresh(); /* restore save modes, repaint screen */ |
| </pre> |
| |
| <h3><a name="xterm" id="xterm">Using NCURSES under XTERM</a></h3> |
| |
| <p>A resize operation in X sends <code>SIGWINCH</code> to the |
| application running under xterm. The easiest way to handle |
| <code>SIGWINCH</code> is to do an <code>endwin</code>, followed |
| by an <code>refresh</code> and a screen repaint you code |
| yourself. The <code>refresh</code> will pick up the new screen |
| size from the xterm's environment.</p> |
| |
| <p>That is the standard way, of course (it even works with some |
| vendor's curses implementations). Its drawback is that it clears |
| the screen to reinitialize the display, and does not resize |
| subwindows which must be shrunk. <code>Ncurses</code> provides an |
| extension which works better, the <code>resizeterm</code> |
| function. That function ensures that all windows are limited to |
| the new screen dimensions, and pads <code>stdscr</code> with |
| blanks if the screen is larger.</p> |
| |
| <p>The <code>ncurses</code> library provides a SIGWINCH signal |
| handler, which pushes a <code>KEY_RESIZE</code> via the wgetch() |
| calls. When <code>ncurses</code> returns that code, it calls |
| <code>resizeterm</code> to update the size of the standard |
| screen's window, repainting that (filling with blanks or |
| truncating as needed). It also resizes other windows, but its |
| effect may be less satisfactory because it cannot know how you |
| want the screen re-painted. You will usually have to write |
| special-purpose code to handle <code>KEY_RESIZE</code> |
| yourself.</p> |
| |
| <h3><a name="screens" id="screens">Handling Multiple Terminal |
| Screens</a></h3> |
| |
| <p>The <code>initscr()</code> function actually calls a function |
| named <code>newterm()</code> to do most of its work. If you are |
| writing a program that opens multiple terminals, use |
| <code>newterm()</code> directly.</p> |
| |
| <p>For each call, you will have to specify a terminal type and a |
| pair of file pointers; each call will return a screen reference, |
| and <code>stdscr</code> will be set to the last one allocated. |
| You will switch between screens with the <code>set_term</code> |
| call. Note that you will also have to call |
| <code>def_shell_mode</code> and <code>def_prog_mode</code> on |
| each tty yourself.</p> |
| |
| <h3><a name="testing" id="testing">Testing for Terminal |
| Capabilities</a></h3> |
| |
| <p>Sometimes you may want to write programs that test for the |
| presence of various capabilities before deciding whether to go |
| into <code>ncurses</code> mode. An easy way to do this is to call |
| <code>setupterm()</code>, then use the functions |
| <code>tigetflag()</code>, <code>tigetnum()</code>, and |
| <code>tigetstr()</code> to do your testing.</p> |
| |
| <p>A particularly useful case of this often comes up when you |
| want to test whether a given terminal type should be treated as |
| “smart” (cursor-addressable) or “stupid”. |
| The right way to test this is to see if the return value of |
| <code>tigetstr("cup")</code> is non-NULL. Alternatively, you can |
| include the <code>term.h</code> file and test the value of the |
| macro <code>cursor_address</code>.</p> |
| |
| <h3><a name="tuning" id="tuning">Tuning for Speed</a></h3> |
| |
| <p>Use the <code>addchstr()</code> family of functions for fast |
| screen-painting of text when you know the text does not contain |
| any control characters. Try to make attribute changes infrequent |
| on your screens. Do not use the <code>immedok()</code> |
| option!</p> |
| |
| <h3><a name="special" id="special">Special Features of |
| NCURSES</a></h3> |
| |
| <p>The <code>wresize()</code> function allows you to resize a |
| window in place. The associated <code>resizeterm()</code> |
| function simplifies the construction of <a href= |
| "#xterm">SIGWINCH</a> handlers, for resizing all windows.</p> |
| |
| <p>The <code>define_key()</code> function allows you to define at |
| runtime function-key control sequences which are not in the |
| terminal description. The <code>keyok()</code> function allows |
| you to temporarily enable or disable interpretation of any |
| function-key control sequence.</p> |
| |
| <p>The <code>use_default_colors()</code> function allows you to |
| construct applications which can use the terminal's default |
| foreground and background colors as an additional "default" |
| color. Several terminal emulators support this feature, which is |
| based on ISO 6429.</p> |
| |
| <p>Ncurses supports up 16 colors, unlike SVr4 curses which |
| defines only 8. While most terminals which provide color allow |
| only 8 colors, about a quarter (including XFree86 xterm) support |
| 16 colors.</p> |
| |
| <h2><a name="compat" id="compat">Compatibility with Older |
| Versions</a></h2> |
| |
| <p>Despite our best efforts, there are some differences between |
| <code>ncurses</code> and the (undocumented!) behavior of older |
| curses implementations. These arise from ambiguities or omissions |
| in the documentation of the API.</p> |
| |
| <h3><a name="refbug" id="refbug">Refresh of Overlapping |
| Windows</a></h3> |
| |
| <p>If you define two windows A and B that overlap, and then |
| alternately scribble on and refresh them, the changes made to the |
| overlapping region under historic <code>curses</code> versions |
| were often not documented precisely.</p> |
| |
| <p>To understand why this is a problem, remember that screen |
| updates are calculated between two representations of the |
| <em>entire</em> display. The documentation says that when you |
| refresh a window, it is first copied to the virtual screen, and |
| then changes are calculated to update the physical screen (and |
| applied to the terminal). But "copied to" is not very specific, |
| and subtle differences in how copying works can produce different |
| behaviors in the case where two overlapping windows are each |
| being refreshed at unpredictable intervals.</p> |
| |
| <p>What happens to the overlapping region depends on what |
| <code>wnoutrefresh()</code> does with its argument -- what |
| portions of the argument window it copies to the virtual screen. |
| Some implementations do "change copy", copying down only |
| locations in the window that have changed (or been marked changed |
| with <code>wtouchln()</code> and friends). Some implementations |
| do "entire copy", copying <em>all</em> window locations to the |
| virtual screen whether or not they have changed.</p> |
| |
| <p>The <code>ncurses</code> library itself has not always been |
| consistent on this score. Due to a bug, versions 1.8.7 to 1.9.8a |
| did entire copy. Versions 1.8.6 and older, and versions 1.9.9 and |
| newer, do change copy.</p> |
| |
| <p>For most commercial curses implementations, it is not |
| documented and not known for sure (at least not to the |
| <code>ncurses</code> maintainers) whether they do change copy or |
| entire copy. We know that System V release 3 curses has logic in |
| it that looks like an attempt to do change copy, but the |
| surrounding logic and data representations are sufficiently |
| complex, and our knowledge sufficiently indirect, that it is hard |
| to know whether this is reliable. It is not clear what the SVr4 |
| documentation and XSI standard intend. The XSI Curses standard |
| barely mentions wnoutrefresh(); the SVr4 documents seem to be |
| describing entire-copy, but it is possible with some effort and |
| straining to read them the other way.</p> |
| |
| <p>It might therefore be unwise to rely on either behavior in |
| programs that might have to be linked with other curses |
| implementations. Instead, you can do an explicit |
| <code>touchwin()</code> before the <code>wnoutrefresh()</code> |
| call to guarantee an entire-contents copy anywhere.</p> |
| |
| <p>The really clean way to handle this is to use the panels |
| library. If, when you want a screen update, you do |
| <code>update_panels()</code>, it will do all the necessary |
| <code>wnoutrefresh()</code> calls for whatever panel stacking |
| order you have defined. Then you can do one |
| <code>doupdate()</code> and there will be a <em>single</em> burst |
| of physical I/O that will do all your updates.</p> |
| |
| <h3><a name="backbug" id="backbug">Background Erase</a></h3> |
| |
| <p>If you have been using a very old versions of |
| <code>ncurses</code> (1.8.7 or older) you may be surprised by the |
| behavior of the erase functions. In older versions, erased areas |
| of a window were filled with a blank modified by the window's |
| current attribute (as set by <strong>wattrset()</strong>, |
| <strong>wattron()</strong>, <strong>wattroff()</strong> and |
| friends).</p> |
| |
| <p>In newer versions, this is not so. Instead, the attribute of |
| erased blanks is normal unless and until it is modified by the |
| functions <code>bkgdset()</code> or <code>wbkgdset()</code>.</p> |
| |
| <p>This change in behavior conforms <code>ncurses</code> to |
| System V Release 4 and the XSI Curses standard.</p> |
| |
| <h2><a name="xsifuncs" id="xsifuncs">XSI Curses Conformance</a></h2> |
| |
| <p>The <code>ncurses</code> library is intended to be base-level |
| conformant with the XSI Curses standard from X/Open. Many |
| extended-level features (in fact, almost all features not |
| directly concerned with wide characters and internationalization) |
| are also supported.</p> |
| |
| <p>One effect of XSI conformance is the change in behavior |
| described under <a href="#backbug">"Background Erase -- |
| Compatibility with Old Versions"</a>.</p> |
| |
| <p>Also, <code>ncurses</code> meets the XSI requirement that |
| every macro entry point have a corresponding function which may |
| be linked (and will be prototype-checked) if the macro definition |
| is disabled with <code>#undef</code>.</p> |
| |
| <h1><a name="panels" id="panels">The Panels Library</a></h1> |
| |
| <p>The <code>ncurses</code> library by itself provides good |
| support for screen displays in which the windows are tiled |
| (non-overlapping). In the more general case that windows may |
| overlap, you have to use a series of <code>wnoutrefresh()</code> |
| calls followed by a <code>doupdate()</code>, and be careful about |
| the order you do the window refreshes in. It has to be |
| bottom-upwards, otherwise parts of windows that should be |
| obscured will show through.</p> |
| |
| <p>When your interface design is such that windows may dive |
| deeper into the visibility stack or pop to the top at runtime, |
| the resulting book-keeping can be tedious and difficult to get |
| right. Hence the panels library.</p> |
| |
| <p>The <code>panel</code> library first appeared in AT&T |
| System V. The version documented here is the <code>panel</code> |
| code distributed with <code>ncurses</code>.</p> |
| |
| <h2><a name="pcompile" id="pcompile">Compiling With the Panels |
| Library</a></h2> |
| |
| <p>Your panels-using modules must import the panels library |
| declarations with</p> |
| |
| <pre> |
| #include <panel.h> |
| </pre> |
| |
| <p>and must be linked explicitly with the panels library using an |
| <code>-lpanel</code> argument. Note that they must also link the |
| <code>ncurses</code> library with <code>-lncurses</code>. Many |
| linkers are two-pass and will accept either order, but it is |
| still good practice to put <code>-lpanel</code> first and |
| <code>-lncurses</code> second.</p> |
| |
| <h2><a name="poverview" id="poverview">Overview of Panels</a></h2> |
| |
| <p>A panel object is a window that is implicitly treated as part |
| of a <dfn>deck</dfn> including all other panel objects. The deck |
| has an implicit bottom-to-top visibility order. The panels |
| library includes an update function (analogous to |
| <code>refresh()</code>) that displays all panels in the deck in |
| the proper order to resolve overlaps. The standard window, |
| <code>stdscr</code>, is considered below all panels.</p> |
| |
| <p>Details on the panels functions are available in the man |
| pages. We will just hit the highlights here.</p> |
| |
| <p>You create a panel from a window by calling |
| <code>new_panel()</code> on a window pointer. It then becomes the |
| top of the deck. The panel's window is available as the value of |
| <code>panel_window()</code> called with the panel pointer as |
| argument.</p> |
| |
| <p>You can delete a panel (removing it from the deck) with |
| <code>del_panel</code>. This will not deallocate the associated |
| window; you have to do that yourself. You can replace a panel's |
| window with a different window by calling |
| <code>replace_window</code>. The new window may be of different |
| size; the panel code will re-compute all overlaps. This operation |
| does not change the panel's position in the deck.</p> |
| |
| <p>To move a panel's window, use <code>move_panel()</code>. The |
| <code>mvwin()</code> function on the panel's window is not |
| sufficient because it does not update the panels library's |
| representation of where the windows are. This operation leaves |
| the panel's depth, contents, and size unchanged.</p> |
| |
| <p>Two functions (<code>top_panel()</code>, |
| <code>bottom_panel()</code>) are provided for rearranging the |
| deck. The first pops its argument window to the top of the deck; |
| the second sends it to the bottom. Either operation leaves the |
| panel's screen location, contents, and size unchanged.</p> |
| |
| <p>The function <code>update_panels()</code> does all the |
| <code>wnoutrefresh()</code> calls needed to prepare for |
| <code>doupdate()</code> (which you must call yourself, |
| afterwards).</p> |
| |
| <p>Typically, you will want to call <code>update_panels()</code> |
| and <code>doupdate()</code> just before accepting command input, |
| once in each cycle of interaction with the user. If you call |
| <code>update_panels()</code> after each and every panel write, |
| you will generate a lot of unnecessary refresh activity and |
| screen flicker.</p> |
| |
| <h2><a name="pstdscr" id="pstdscr">Panels, Input, and the |
| Standard Screen</a></h2> |
| |
| <p>You should not mix <code>wnoutrefresh()</code> or |
| <code>wrefresh()</code> operations with panels code; this will |
| work only if the argument window is either in the top panel or |
| unobscured by any other panels.</p> |
| |
| <p>The <code>stsdcr</code> window is a special case. It is |
| considered below all panels. Because changes to panels may |
| obscure parts of <code>stdscr</code>, though, you should call |
| <code>update_panels()</code> before <code>doupdate()</code> even |
| when you only change <code>stdscr</code>.</p> |
| |
| <p>Note that <code>wgetch</code> automatically calls |
| <code>wrefresh</code>. Therefore, before requesting input from a |
| panel window, you need to be sure that the panel is totally |
| unobscured.</p> |
| |
| <p>There is presently no way to display changes to one obscured |
| panel without repainting all panels.</p> |
| |
| <h2><a name="hiding" id="hiding">Hiding Panels</a></h2> |
| |
| <p>It is possible to remove a panel from the deck temporarily; |
| use <code>hide_panel</code> for this. Use |
| <code>show_panel()</code> to render it visible again. The |
| predicate function <code>panel_hidden</code> tests whether or not |
| a panel is hidden.</p> |
| |
| <p>The <code>panel_update</code> code ignores hidden panels. You |
| cannot do <code>top_panel()</code> or <code>bottom_panel</code> |
| on a hidden panel(). Other panels operations are applicable.</p> |
| |
| <h2><a name="pmisc" id="pmisc">Miscellaneous Other Facilities</a></h2> |
| |
| <p>It is possible to navigate the deck using the functions |
| <code>panel_above()</code> and <code>panel_below</code>. Handed a |
| panel pointer, they return the panel above or below that panel. |
| Handed <code>NULL</code>, they return the bottom-most or top-most |
| panel.</p> |
| |
| <p>Every panel has an associated user pointer, not used by the |
| panel code, to which you can attach application data. See the man |
| page documentation of <code>set_panel_userptr()</code> and |
| <code>panel_userptr</code> for details.</p> |
| |
| <h1><a name="menu" id="menu">The Menu Library</a></h1> |
| |
| <p>A menu is a screen display that assists the user to choose |
| some subset of a given set of items. The <code>menu</code> |
| library is a curses extension that supports easy programming of |
| menu hierarchies with a uniform but flexible interface.</p> |
| |
| <p>The <code>menu</code> library first appeared in AT&T |
| System V. The version documented here is the <code>menu</code> |
| code distributed with <code>ncurses</code>.</p> |
| |
| <h2><a name="mcompile" id="mcompile">Compiling With the menu |
| Library</a></h2> |
| |
| <p>Your menu-using modules must import the menu library |
| declarations with</p> |
| |
| <pre> |
| #include <menu.h> |
| </pre> |
| |
| <p>and must be linked explicitly with the menus library using an |
| <code>-lmenu</code> argument. Note that they must also link the |
| <code>ncurses</code> library with <code>-lncurses</code>. Many |
| linkers are two-pass and will accept either order, but it is |
| still good practice to put <code>-lmenu</code> first and |
| <code>-lncurses</code> second.</p> |
| |
| <h2><a name="moverview" id="moverview">Overview of Menus</a></h2> |
| |
| <p>The menus created by this library consist of collections of |
| <dfn>items</dfn> including a name string part and a description |
| string part. To make menus, you create groups of these items and |
| connect them with menu frame objects.</p> |
| |
| <p>The menu can then by <dfn>posted</dfn>, that is written to an |
| associated window. Actually, each menu has two associated |
| windows; a containing window in which the programmer can scribble |
| titles or borders, and a subwindow in which the menu items proper |
| are displayed. If this subwindow is too small to display all the |
| items, it will be a scrollable viewport on the collection of |
| items.</p> |
| |
| <p>A menu may also be <dfn>unposted</dfn> (that is, undisplayed), |
| and finally freed to make the storage associated with it and its |
| items available for re-use.</p> |
| |
| <p>The general flow of control of a menu program looks like |
| this:</p> |
| |
| <ol> |
| <li>Initialize <code>curses</code>.</li> |
| |
| <li>Create the menu items, using <code>new_item()</code>.</li> |
| |
| <li>Create the menu using <code>new_menu()</code>.</li> |
| |
| <li>Post the menu using <code>post_menu()</code>.</li> |
| |
| <li>Refresh the screen.</li> |
| |
| <li>Process user requests via an input loop.</li> |
| |
| <li>Unpost the menu using <code>unpost_menu()</code>.</li> |
| |
| <li>Free the menu, using <code>free_menu()</code>.</li> |
| |
| <li>Free the items using <code>free_item()</code>.</li> |
| |
| <li>Terminate <code>curses</code>.</li> |
| </ol> |
| |
| <h2><a name="mselect" id="mselect">Selecting items</a></h2> |
| |
| <p>Menus may be multi-valued or (the default) single-valued (see |
| the manual page <code>menu_opts(3x)</code> to see how to change |
| the default). Both types always have a <dfn>current |
| item</dfn>.</p> |
| |
| <p>From a single-valued menu you can read the selected value |
| simply by looking at the current item. From a multi-valued menu, |
| you get the selected set by looping through the items applying |
| the <code>item_value()</code> predicate function. Your |
| menu-processing code can use the function |
| <code>set_item_value()</code> to flag the items in the select |
| set.</p> |
| |
| <p>Menu items can be made unselectable using |
| <code>set_item_opts()</code> or <code>item_opts_off()</code> with |
| the <code>O_SELECTABLE</code> argument. This is the only option |
| so far defined for menus, but it is good practice to code as |
| though other option bits might be on.</p> |
| |
| <h2><a name="mdisplay" id="mdisplay">Menu Display</a></h2> |
| |
| <p>The menu library calculates a minimum display size for your |
| window, based on the following variables:</p> |
| |
| <ul> |
| <li>The number and maximum length of the menu items</li> |
| |
| <li>Whether the O_ROWMAJOR option is enabled</li> |
| |
| <li>Whether display of descriptions is enabled</li> |
| |
| <li>Whatever menu format may have been set by the |
| programmer</li> |
| |
| <li>The length of the menu mark string used for highlighting |
| selected items</li> |
| </ul> |
| |
| <p>The function <code>set_menu_format()</code> allows you to set |
| the maximum size of the viewport or <dfn>menu page</dfn> that |
| will be used to display menu items. You can retrieve any format |
| associated with a menu with <code>menu_format()</code>. The |
| default format is rows=16, columns=1.</p> |
| |
| <p>The actual menu page may be smaller than the format size. This |
| depends on the item number and size and whether O_ROWMAJOR is on. |
| This option (on by default) causes menu items to be displayed in |
| a “raster-scan” pattern, so that if more than one |
| item will fit horizontally the first couple of items are |
| side-by-side in the top row. The alternative is column-major |
| display, which tries to put the first several items in the first |
| column.</p> |
| |
| <p>As mentioned above, a menu format not large enough to allow |
| all items to fit on-screen will result in a menu display that is |
| vertically scrollable.</p> |
| |
| <p>You can scroll it with requests to the menu driver, which will |
| be described in the section on <a href="#minput">menu input |
| handling</a>.</p> |
| |
| <p>Each menu has a <dfn>mark string</dfn> used to visually tag |
| selected items; see the <code>menu_mark(3x)</code> manual page |
| for details. The mark string length also influences the menu page |
| size.</p> |
| |
| <p>The function <code>scale_menu()</code> returns the minimum |
| display size that the menu code computes from all these factors. |
| There are other menu display attributes including a select |
| attribute, an attribute for selectable items, an attribute for |
| unselectable items, and a pad character used to separate item |
| name text from description text. These have reasonable defaults |
| which the library allows you to change (see the |
| <code>menu_attribs(3x)</code> manual page.</p> |
| |
| <h2><a name="mwindows" id="mwindows">Menu Windows</a></h2> |
| |
| <p>Each menu has, as mentioned previously, a pair of associated |
| windows. Both these windows are painted when the menu is posted |
| and erased when the menu is unposted.</p> |
| |
| <p>The outer or frame window is not otherwise touched by the menu |
| routines. It exists so the programmer can associate a title, a |
| border, or perhaps help text with the menu and have it properly |
| refreshed or erased at post/unpost time. The inner window or |
| <dfn>subwindow</dfn> is where the current menu page is |
| displayed.</p> |
| |
| <p>By default, both windows are <code>stdscr</code>. You can set |
| them with the functions in <code>menu_win(3x)</code>.</p> |
| |
| <p>When you call <code>post_menu()</code>, you write the menu to |
| its subwindow. When you call <code>unpost_menu()</code>, you |
| erase the subwindow, However, neither of these actually modifies |
| the screen. To do that, call <code>wrefresh()</code> or some |
| equivalent.</p> |
| |
| <h2><a name="minput" id="minput">Processing Menu Input</a></h2> |
| |
| <p>The main loop of your menu-processing code should call |
| <code>menu_driver()</code> repeatedly. The first argument of this |
| routine is a menu pointer; the second is a menu command code. You |
| should write an input-fetching routine that maps input characters |
| to menu command codes, and pass its output to |
| <code>menu_driver()</code>. The menu command codes are fully |
| documented in <code>menu_driver(3x)</code>.</p> |
| |
| <p>The simplest group of command codes is |
| <code>REQ_NEXT_ITEM</code>, <code>REQ_PREV_ITEM</code>, |
| <code>REQ_FIRST_ITEM</code>, <code>REQ_LAST_ITEM</code>, |
| <code>REQ_UP_ITEM</code>, <code>REQ_DOWN_ITEM</code>, |
| <code>REQ_LEFT_ITEM</code>, <code>REQ_RIGHT_ITEM</code>. These |
| change the currently selected item. These requests may cause |
| scrolling of the menu page if it only partially displayed.</p> |
| |
| <p>There are explicit requests for scrolling which also change |
| the current item (because the select location does not change, |
| but the item there does). These are <code>REQ_SCR_DLINE</code>, |
| <code>REQ_SCR_ULINE</code>, <code>REQ_SCR_DPAGE</code>, and |
| <code>REQ_SCR_UPAGE</code>.</p> |
| |
| <p>The <code>REQ_TOGGLE_ITEM</code> selects or deselects the |
| current item. It is for use in multi-valued menus; if you use it |
| with <code>O_ONEVALUE</code> on, you will get an error return |
| (<code>E_REQUEST_DENIED</code>).</p> |
| |
| <p>Each menu has an associated pattern buffer. The |
| <code>menu_driver()</code> logic tries to accumulate printable |
| ASCII characters passed in in that buffer; when it matches a |
| prefix of an item name, that item (or the next matching item) is |
| selected. If appending a character yields no new match, that |
| character is deleted from the pattern buffer, and |
| <code>menu_driver()</code> returns <code>E_NO_MATCH</code>.</p> |
| |
| <p>Some requests change the pattern buffer directly: |
| <code>REQ_CLEAR_PATTERN</code>, <code>REQ_BACK_PATTERN</code>, |
| <code>REQ_NEXT_MATCH</code>, <code>REQ_PREV_MATCH</code>. The |
| latter two are useful when pattern buffer input matches more than |
| one item in a multi-valued menu.</p> |
| |
| <p>Each successful scroll or item navigation request clears the |
| pattern buffer. It is also possible to set the pattern buffer |
| explicitly with <code>set_menu_pattern()</code>.</p> |
| |
| <p>Finally, menu driver requests above the constant |
| <code>MAX_COMMAND</code> are considered application-specific |
| commands. The <code>menu_driver()</code> code ignores them and |
| returns <code>E_UNKNOWN_COMMAND</code>.</p> |
| |
| <h2><a name="mmisc" id="mmisc">Miscellaneous Other Features</a></h2> |
| |
| <p>Various menu options can affect the processing and visual |
| appearance and input processing of menus. See <code>menu_opts(3x) |
| for details.</code></p> |
| |
| <p>It is possible to change the current item from application |
| code; this is useful if you want to write your own navigation |
| requests. It is also possible to explicitly set the top row of |
| the menu display. See <code>mitem_current(3x)</code>. If your |
| application needs to change the menu subwindow cursor for any |
| reason, <code>pos_menu_cursor()</code> will restore it to the |
| correct location for continuing menu driver processing.</p> |
| |
| <p>It is possible to set hooks to be called at menu |
| initialization and wrapup time, and whenever the selected item |
| changes. See <code>menu_hook(3x)</code>.</p> |
| |
| <p>Each item, and each menu, has an associated user pointer on |
| which you can hang application data. See |
| <code>mitem_userptr(3x)</code> and |
| <code>menu_userptr(3x)</code>.</p> |
| |
| <h1><a name="form" id="form">The Forms Library</a></h1> |
| |
| <p>The <code>form</code> library is a curses extension that |
| supports easy programming of on-screen forms for data entry and |
| program control.</p> |
| |
| <p>The <code>form</code> library first appeared in AT&T |
| System V. The version documented here is the <code>form</code> |
| code distributed with <code>ncurses</code>.</p> |
| |
| <h2><a name="fcompile" id="fcompile">Compiling With the form |
| Library</a></h2> |
| |
| <p>Your form-using modules must import the form library |
| declarations with</p> |
| |
| <pre> |
| #include <form.h> |
| </pre> |
| |
| <p>and must be linked explicitly with the forms library using an |
| <code>-lform</code> argument. Note that they must also link the |
| <code>ncurses</code> library with <code>-lncurses</code>. Many |
| linkers are two-pass and will accept either order, but it is |
| still good practice to put <code>-lform</code> first and |
| <code>-lncurses</code> second.</p> |
| |
| <h2><a name="foverview" id="foverview">Overview of Forms</a></h2> |
| |
| <p>A form is a collection of fields; each field may be either a |
| label (explanatory text) or a data-entry location. Long forms may |
| be segmented into pages; each entry to a new page clears the |
| screen.</p> |
| |
| <p>To make forms, you create groups of fields and connect them |
| with form frame objects; the form library makes this relatively |
| simple.</p> |
| |
| <p>Once defined, a form can be <dfn>posted</dfn>, that is written |
| to an associated window. Actually, each form has two associated |
| windows; a containing window in which the programmer can scribble |
| titles or borders, and a subwindow in which the form fields |
| proper are displayed.</p> |
| |
| <p>As the form user fills out the posted form, navigation and |
| editing keys support movement between fields, editing keys |
| support modifying field, and plain text adds to or changes data |
| in a current field. The form library allows you (the forms |
| designer) to bind each navigation and editing key to any |
| keystroke accepted by <code>curses</code> Fields may have |
| validation conditions on them, so that they check input data for |
| type and value. The form library supplies a rich set of |
| pre-defined field types, and makes it relatively easy to define |
| new ones.</p> |
| |
| <p>Once its transaction is completed (or aborted), a form may be |
| <dfn>unposted</dfn> (that is, undisplayed), and finally freed to |
| make the storage associated with it and its items available for |
| re-use.</p> |
| |
| <p>The general flow of control of a form program looks like |
| this:</p> |
| |
| <ol> |
| <li>Initialize <code>curses</code>.</li> |
| |
| <li>Create the form fields, using |
| <code>new_field()</code>.</li> |
| |
| <li>Create the form using <code>new_form()</code>.</li> |
| |
| <li>Post the form using <code>post_form()</code>.</li> |
| |
| <li>Refresh the screen.</li> |
| |
| <li>Process user requests via an input loop.</li> |
| |
| <li>Unpost the form using <code>unpost_form()</code>.</li> |
| |
| <li>Free the form, using <code>free_form()</code>.</li> |
| |
| <li>Free the fields using <code>free_field()</code>.</li> |
| |
| <li>Terminate <code>curses</code>.</li> |
| </ol> |
| |
| <p>Note that this looks much like a menu program; the form |
| library handles tasks which are in many ways similar, and its |
| interface was obviously designed to resemble that of the <a href= |
| "#menu">menu library</a> wherever possible.</p> |
| |
| <p>In forms programs, however, the “process user |
| requests” is somewhat more complicated than for menus. |
| Besides menu-like navigation operations, the menu driver loop has |
| to support field editing and data validation.</p> |
| |
| <h2><a name="fcreate" id="fcreate">Creating and Freeing Fields |
| and Forms</a></h2> |
| |
| <p>The basic function for creating fields is |
| <code>new_field()</code>:</p> |
| |
| <pre> |
| FIELD *new_field(int height, int width, /* new field size */ |
| int top, int left, /* upper left corner */ |
| int offscreen, /* number of offscreen rows */ |
| int nbuf); /* number of working buffers */ |
| </pre> |
| |
| <p>Menu items always occupy a single row, but forms fields may |
| have multiple rows. So <code>new_field()</code> requires you to |
| specify a width and height (the first two arguments, which mist |
| both be greater than zero).</p> |
| |
| <p>You must also specify the location of the field's upper left |
| corner on the screen (the third and fourth arguments, which must |
| be zero or greater). Note that these coordinates are relative to |
| the form subwindow, which will coincide with <code>stdscr</code> |
| by default but need not be <code>stdscr</code> if you have done |
| an explicit <code>set_form_win()</code> call.</p> |
| |
| <p>The fifth argument allows you to specify a number of |
| off-screen rows. If this is zero, the entire field will always be |
| displayed. If it is nonzero, the form will be scrollable, with |
| only one screen-full (initially the top part) displayed at any |
| given time. If you make a field dynamic and grow it so it will no |
| longer fit on the screen, the form will become scrollable even if |
| the <code>offscreen</code> argument was initially zero.</p> |
| |
| <p>The forms library allocates one working buffer per field; the |
| size of each buffer is <code>((height + offscreen)*width + |
| 1</code>, one character for each position in the field plus a NUL |
| terminator. The sixth argument is the number of additional data |
| buffers to allocate for the field; your application can use them |
| for its own purposes.</p> |
| |
| <pre> |
| FIELD *dup_field(FIELD *field, /* field to copy */ |
| int top, int left); /* location of new copy */ |
| </pre> |
| |
| <p>The function <code>dup_field()</code> duplicates an existing |
| field at a new location. Size and buffering information are |
| copied; some attribute flags and status bits are not (see the |
| <code>form_field_new(3X)</code> for details).</p> |
| |
| <pre> |
| FIELD *link_field(FIELD *field, /* field to copy */ |
| int top, int left); /* location of new copy */ |
| </pre> |
| |
| <p>The function <code>link_field()</code> also duplicates an |
| existing field at a new location. The difference from |
| <code>dup_field()</code> is that it arranges for the new field's |
| buffer to be shared with the old one.</p> |
| |
| <p>Besides the obvious use in making a field editable from two |
| different form pages, linked fields give you a way to hack in |
| dynamic labels. If you declare several fields linked to an |
| original, and then make them inactive, changes from the original |
| will still be propagated to the linked fields.</p> |
| |
| <p>As with duplicated fields, linked fields have attribute bits |
| separate from the original.</p> |
| |
| <p>As you might guess, all these field-allocations return |
| <code>NULL</code> if the field allocation is not possible due to |
| an out-of-memory error or out-of-bounds arguments.</p> |
| |
| <p>To connect fields to a form, use</p> |
| |
| <pre> |
| FORM *new_form(FIELD **fields); |
| </pre> |
| |
| <p>This function expects to see a NULL-terminated array of field |
| pointers. Said fields are connected to a newly-allocated form |
| object; its address is returned (or else NULL if the allocation |
| fails).</p> |
| |
| <p>Note that <code>new_field()</code> does <em>not</em> copy the |
| pointer array into private storage; if you modify the contents of |
| the pointer array during forms processing, all manner of bizarre |
| things might happen. Also note that any given field may only be |
| connected to one form.</p> |
| |
| <p>The functions <code>free_field()</code> and |
| <code>free_form</code> are available to free field and form |
| objects. It is an error to attempt to free a field connected to a |
| form, but not vice-versa; thus, you will generally free your form |
| objects first.</p> |
| |
| <h2><a name="fattributes" id="fattributes">Fetching and Changing |
| Field Attributes</a></h2> |
| |
| <p>Each form field has a number of location and size attributes |
| associated with it. There are other field attributes used to |
| control display and editing of the field. Some (for example, the |
| <code>O_STATIC</code> bit) involve sufficient complications to be |
| covered in sections of their own later on. We cover the functions |
| used to get and set several basic attributes here.</p> |
| |
| <p>When a field is created, the attributes not specified by the |
| <code>new_field</code> function are copied from an invisible |
| system default field. In attribute-setting and -fetching |
| functions, the argument NULL is taken to mean this field. Changes |
| to it persist as defaults until your forms application |
| terminates.</p> |
| |
| <h3><a name="fsizes" id="fsizes">Fetching Size and Location |
| Data</a></h3> |
| |
| <p>You can retrieve field sizes and locations through:</p> |
| |
| <pre> |
| int field_info(FIELD *field, /* field from which to fetch */ |
| int *height, *int width, /* field size */ |
| int *top, int *left, /* upper left corner */ |
| int *offscreen, /* number of offscreen rows */ |
| int *nbuf); /* number of working buffers */ |
| </pre> |
| |
| <p>This function is a sort of inverse of |
| <code>new_field()</code>; instead of setting size and location |
| attributes of a new field, it fetches them from an existing |
| one.</p> |
| |
| <h3><a name="flocation" id="flocation">Changing the Field |
| Location</a></h3> |
| |
| <p>It is possible to move a field's location on the screen:</p> |
| |
| <pre> |
| int move_field(FIELD *field, /* field to alter */ |
| int top, int left); /* new upper-left corner */ |
| </pre> |
| |
| <p>You can, of course. query the current location through |
| <code>field_info()</code>.</p> |
| |
| <h3><a name="fjust" id="fjust">The Justification Attribute</a></h3> |
| |
| <p>One-line fields may be unjustified, justified right, justified |
| left, or centered. Here is how you manipulate this attribute:</p> |
| |
| <pre> |
| int set_field_just(FIELD *field, /* field to alter */ |
| int justmode); /* mode to set */ |
| |
| int field_just(FIELD *field); /* fetch mode of field */ |
| </pre> |
| |
| <p>The mode values accepted and returned by this functions are |
| preprocessor macros <code>NO_JUSTIFICATION</code>, |
| <code>JUSTIFY_RIGHT</code>, <code>JUSTIFY_LEFT</code>, or |
| <code>JUSTIFY_CENTER</code>.</p> |
| |
| <h3><a name="fdispatts" id="fdispatts">Field Display |
| Attributes</a></h3> |
| |
| <p>For each field, you can set a foreground attribute for entered |
| characters, a background attribute for the entire field, and a |
| pad character for the unfilled portion of the field. You can also |
| control pagination of the form.</p> |
| |
| <p>This group of four field attributes controls the visual |
| appearance of the field on the screen, without affecting in any |
| way the data in the field buffer.</p> |
| |
| <pre> |
| int set_field_fore(FIELD *field, /* field to alter */ |
| chtype attr); /* attribute to set */ |
| |
| chtype field_fore(FIELD *field); /* field to query */ |
| |
| int set_field_back(FIELD *field, /* field to alter */ |
| chtype attr); /* attribute to set */ |
| |
| chtype field_back(FIELD *field); /* field to query */ |
| |
| int set_field_pad(FIELD *field, /* field to alter */ |
| int pad); /* pad character to set */ |
| |
| chtype field_pad(FIELD *field); |
| |
| int set_new_page(FIELD *field, /* field to alter */ |
| int flag); /* TRUE to force new page */ |
| |
| chtype new_page(FIELD *field); /* field to query */ |
| </pre> |
| |
| <p>The attributes set and returned by the first four functions |
| are normal <code>curses(3x)</code> display attribute values |
| (<code>A_STANDOUT</code>, <code>A_BOLD</code>, |
| <code>A_REVERSE</code> etc). The page bit of a field controls |
| whether it is displayed at the start of a new form screen.</p> |
| |
| <h3><a name="foptions" id="foptions">Field Option Bits</a></h3> |
| |
| <p>There is also a large collection of field option bits you can |
| set to control various aspects of forms processing. You can |
| manipulate them with these functions:</p> |
| |
| <pre> |
| int set_field_opts(FIELD *field, /* field to alter */ |
| int attr); /* attribute to set */ |
| |
| int field_opts_on(FIELD *field, /* field to alter */ |
| int attr); /* attributes to turn on */ |
| |
| int field_opts_off(FIELD *field, /* field to alter */ |
| int attr); /* attributes to turn off */ |
| |
| int field_opts(FIELD *field); /* field to query */ |
| </pre> |
| |
| <p>By default, all options are on. Here are the available option |
| bits:</p> |
| |
| <dl> |
| <dt>O_VISIBLE</dt> |
| |
| <dd>Controls whether the field is visible on the screen. Can be |
| used during form processing to hide or pop up fields depending |
| on the value of parent fields.</dd> |
| |
| <dt>O_ACTIVE</dt> |
| |
| <dd>Controls whether the field is active during forms |
| processing (i.e. visited by form navigation keys). Can be used |
| to make labels or derived fields with buffer values alterable |
| by the forms application, not the user.</dd> |
| |
| <dt>O_PUBLIC</dt> |
| |
| <dd>Controls whether data is displayed during field entry. If |
| this option is turned off on a field, the library will accept |
| and edit data in that field, but it will not be displayed and |
| the visible field cursor will not move. You can turn off the |
| O_PUBLIC bit to define password fields.</dd> |
| |
| <dt>O_EDIT</dt> |
| |
| <dd>Controls whether the field's data can be modified. When |
| this option is off, all editing requests except |
| <code>REQ_PREV_CHOICE</code> and <code>REQ_NEXT_CHOICE</code> |
| will fail. Such read-only fields may be useful for help |
| messages.</dd> |
| |
| <dt>O_WRAP</dt> |
| |
| <dd>Controls word-wrapping in multi-line fields. Normally, when |
| any character of a (blank-separated) word reaches the end of |
| the current line, the entire word is wrapped to the next line |
| (assuming there is one). When this option is off, the word will |
| be split across the line break.</dd> |
| |
| <dt>O_BLANK</dt> |
| |
| <dd>Controls field blanking. When this option is on, entering a |
| character at the first field position erases the entire field |
| (except for the just-entered character).</dd> |
| |
| <dt>O_AUTOSKIP</dt> |
| |
| <dd>Controls automatic skip to next field when this one fills. |
| Normally, when the forms user tries to type more data into a |
| field than will fit, the editing location jumps to next field. |
| When this option is off, the user's cursor will hang at the end |
| of the field. This option is ignored in dynamic fields that |
| have not reached their size limit.</dd> |
| |
| <dt>O_NULLOK</dt> |
| |
| <dd>Controls whether <a href="#fvalidation">validation</a> is |
| applied to blank fields. Normally, it is not; the user can |
| leave a field blank without invoking the usual validation check |
| on exit. If this option is off on a field, exit from it will |
| invoke a validation check.</dd> |
| |
| <dt>O_PASSOK</dt> |
| |
| <dd>Controls whether validation occurs on every exit, or only |
| after the field is modified. Normally the latter is true. |
| Setting O_PASSOK may be useful if your field's validation |
| function may change during forms processing.</dd> |
| |
| <dt>O_STATIC</dt> |
| |
| <dd>Controls whether the field is fixed to its initial |
| dimensions. If you turn this off, the field becomes <a href= |
| "#fdynamic">dynamic</a> and will stretch to fit entered |
| data.</dd> |
| </dl> |
| |
| <p>A field's options cannot be changed while the field is |
| currently selected. However, options may be changed on posted |
| fields that are not current.</p> |
| |
| <p>The option values are bit-masks and can be composed with |
| logical-or in the obvious way.</p> |
| |
| <h2><a name="fstatus" id="fstatus">Field Status</a></h2> |
| |
| <p>Every field has a status flag, which is set to FALSE when the |
| field is created and TRUE when the value in field buffer 0 |
| changes. This flag can be queried and set directly:</p> |
| |
| <pre> |
| int set_field_status(FIELD *field, /* field to alter */ |
| int status); /* mode to set */ |
| |
| int field_status(FIELD *field); /* fetch mode of field */ |
| </pre> |
| |
| <p>Setting this flag under program control can be useful if you |
| use the same form repeatedly, looking for modified fields each |
| time.</p> |
| |
| <p>Calling <code>field_status()</code> on a field not currently |
| selected for input will return a correct value. Calling |
| <code>field_status()</code> on a field that is currently selected |
| for input may not necessarily give a correct field status value, |
| because entered data is not necessarily copied to buffer zero |
| before the exit validation check. To guarantee that the returned |
| status value reflects reality, call <code>field_status()</code> |
| either (1) in the field's exit validation check routine, (2) from |
| the field's or form's initialization or termination hooks, or (3) |
| just after a <code>REQ_VALIDATION</code> request has been |
| processed by the forms driver.</p> |
| |
| <h2><a name="fuser" id="fuser">Field User Pointer</a></h2> |
| |
| <p>Each field structure contains one character pointer slot that |
| is not used by the forms library. It is intended to be used by |
| applications to store private per-field data. You can manipulate |
| it with:</p> |
| |
| <pre> |
| int set_field_userptr(FIELD *field, /* field to alter */ |
| char *userptr); /* mode to set */ |
| |
| char *field_userptr(FIELD *field); /* fetch mode of field */ |
| </pre>(Properly, this user pointer field ought to have <code>(void |
| *)</code> type. The <code>(char *)</code> type is retained for |
| System V compatibility.) |
| |
| <p>It is valid to set the user pointer of the default field (with |
| a <code>set_field_userptr()</code> call passed a NULL field |
| pointer.) When a new field is created, the default-field user |
| pointer is copied to initialize the new field's user pointer.</p> |
| |
| <h2><a name="fdynamic" id="fdynamic">Variable-Sized Fields</a></h2> |
| |
| <p>Normally, a field is fixed at the size specified for it at |
| creation time. If, however, you turn off its O_STATIC bit, it |
| becomes <dfn>dynamic</dfn> and will automatically resize itself |
| to accommodate data as it is entered. If the field has extra |
| buffers associated with it, they will grow right along with the |
| main input buffer.</p> |
| |
| <p>A one-line dynamic field will have a fixed height (1) but |
| variable width, scrolling horizontally to display data within the |
| field area as originally dimensioned and located. A multi-line |
| dynamic field will have a fixed width, but variable height |
| (number of rows), scrolling vertically to display data within the |
| field area as originally dimensioned and located.</p> |
| |
| <p>Normally, a dynamic field is allowed to grow without limit. |
| But it is possible to set an upper limit on the size of a dynamic |
| field. You do it with this function:</p> |
| |
| <pre> |
| int set_max_field(FIELD *field, /* field to alter (may not be NULL) */ |
| int max_size); /* upper limit on field size */ |
| </pre> |
| |
| <p>If the field is one-line, <code>max_size</code> is taken to be |
| a column size limit; if it is multi-line, it is taken to be a |
| line size limit. To disable any limit, use an argument of zero. |
| The growth limit can be changed whether or not the O_STATIC bit |
| is on, but has no effect until it is.</p> |
| |
| <p>The following properties of a field change when it becomes |
| dynamic:</p> |
| |
| <ul> |
| <li>If there is no growth limit, there is no final position of |
| the field; therefore <code>O_AUTOSKIP</code> and |
| <code>O_NL_OVERLOAD</code> are ignored.</li> |
| |
| <li>Field justification will be ignored (though whatever |
| justification is set up will be retained internally and can be |
| queried).</li> |
| |
| <li>The <code>dup_field()</code> and <code>link_field()</code> |
| calls copy dynamic-buffer sizes. If the <code>O_STATIC</code> |
| option is set on one of a collection of links, buffer resizing |
| will occur only when the field is edited through that |
| link.</li> |
| |
| <li>The call <code>field_info()</code> will retrieve the |
| original static size of the field; use |
| <code>dynamic_field_info()</code> to get the actual dynamic |
| size.</li> |
| </ul> |
| |
| <h2><a name="fvalidation" id="fvalidation">Field Validation</a></h2> |
| |
| <p>By default, a field will accept any data that will fit in its |
| input buffer. However, it is possible to attach a validation type |
| to a field. If you do this, any attempt to leave the field while |
| it contains data that does not match the validation type will |
| fail. Some validation types also have a character-validity check |
| for each time a character is entered in the field.</p> |
| |
| <p>A field's validation check (if any) is not called when |
| <code>set_field_buffer()</code> modifies the input buffer, nor |
| when that buffer is changed through a linked field.</p> |
| |
| <p>The <code>form</code> library provides a rich set of |
| pre-defined validation types, and gives you the capability to |
| define custom ones of your own. You can examine and change field |
| validation attributes with the following functions:</p> |
| |
| <pre> |
| int set_field_type(FIELD *field, /* field to alter */ |
| FIELDTYPE *ftype, /* type to associate */ |
| ...); /* additional arguments*/ |
| |
| FIELDTYPE *field_type(FIELD *field); /* field to query */ |
| </pre> |
| |
| <p>The validation type of a field is considered an attribute of |
| the field. As with other field attributes, Also, doing |
| <code>set_field_type()</code> with a <code>NULL</code> field |
| default will change the system default for validation of |
| newly-created fields.</p> |
| |
| <p>Here are the pre-defined validation types:</p> |
| |
| <h3><a name="ftype_alpha" id="ftype_alpha">TYPE_ALPHA</a></h3> |
| |
| <p>This field type accepts alphabetic data; no blanks, no digits, |
| no special characters (this is checked at character-entry time). |
| It is set up with:</p> |
| |
| <pre> |
| int set_field_type(FIELD *field, /* field to alter */ |
| TYPE_ALPHA, /* type to associate */ |
| int width); /* maximum width of field */ |
| </pre> |
| |
| <p>The <code>width</code> argument sets a minimum width of data. |
| Typically you will want to set this to the field width; if it is |
| greater than the field width, the validation check will always |
| fail. A minimum width of zero makes field completion |
| optional.</p> |
| |
| <h3><a name="ftype_alnum" id="ftype_alnum">TYPE_ALNUM</a></h3> |
| |
| <p>This field type accepts alphabetic data and digits; no blanks, |
| no special characters (this is checked at character-entry time). |
| It is set up with:</p> |
| |
| <pre> |
| int set_field_type(FIELD *field, /* field to alter */ |
| TYPE_ALNUM, /* type to associate */ |
| int width); /* maximum width of field */ |
| </pre> |
| |
| <p>The <code>width</code> argument sets a minimum width of data. |
| As with TYPE_ALPHA, typically you will want to set this to the |
| field width; if it is greater than the field width, the |
| validation check will always fail. A minimum width of zero makes |
| field completion optional.</p> |
| |
| <h3><a name="ftype_enum" id="ftype_enum">TYPE_ENUM</a></h3> |
| |
| <p>This type allows you to restrict a field's values to be among |
| a specified set of string values (for example, the two-letter |
| postal codes for U.S. states). It is set up with:</p> |
| |
| <pre> |
| int set_field_type(FIELD *field, /* field to alter */ |
| TYPE_ENUM, /* type to associate */ |
| char **valuelist; /* list of possible values */ |
| int checkcase; /* case-sensitive? */ |
| int checkunique); /* must specify uniquely? */ |
| </pre> |
| |
| <p>The <code>valuelist</code> parameter must point at a |
| NULL-terminated list of valid strings. The <code>checkcase</code> |
| argument, if true, makes comparison with the string |
| case-sensitive.</p> |
| |
| <p>When the user exits a TYPE_ENUM field, the validation |
| procedure tries to complete the data in the buffer to a valid |
| entry. If a complete choice string has been entered, it is of |
| course valid. But it is also possible to enter a prefix of a |
| valid string and have it completed for you.</p> |
| |
| <p>By default, if you enter such a prefix and it matches more |
| than one value in the string list, the prefix will be completed |
| to the first matching value. But the <code>checkunique</code> |
| argument, if true, requires prefix matches to be unique in order |
| to be valid.</p> |
| |
| <p>The <code>REQ_NEXT_CHOICE</code> and |
| <code>REQ_PREV_CHOICE</code> input requests can be particularly |
| useful with these fields.</p> |
| |
| <h3><a name="ftype_integer" id="ftype_integer">TYPE_INTEGER</a></h3> |
| |
| <p>This field type accepts an integer. It is set up as |
| follows:</p> |
| |
| <pre> |
| int set_field_type(FIELD *field, /* field to alter */ |
| TYPE_INTEGER, /* type to associate */ |
| int padding, /* # places to zero-pad to */ |
| int vmin, int vmax); /* valid range */ |
| </pre> |
| |
| <p>Valid characters consist of an optional leading minus and |
| digits. The range check is performed on exit. If the range |
| maximum is less than or equal to the minimum, the range is |
| ignored.</p> |
| |
| <p>If the value passes its range check, it is padded with as many |
| leading zero digits as necessary to meet the padding |
| argument.</p> |
| |
| <p>A <code>TYPE_INTEGER</code> value buffer can conveniently be |
| interpreted with the C library function <code>atoi(3)</code>.</p> |
| |
| <h3><a name="ftype_numeric" id="ftype_numeric">TYPE_NUMERIC</a></h3> |
| |
| <p>This field type accepts a decimal number. It is set up as |
| follows:</p> |
| |
| <pre> |
| int set_field_type(FIELD *field, /* field to alter */ |
| TYPE_NUMERIC, /* type to associate */ |
| int padding, /* # places of precision */ |
| double vmin, double vmax); /* valid range */ |
| </pre> |
| |
| <p>Valid characters consist of an optional leading minus and |
| digits. possibly including a decimal point. If your system |
| supports locale's, the decimal point character used must be the |
| one defined by your locale. The range check is performed on exit. |
| If the range maximum is less than or equal to the minimum, the |
| range is ignored.</p> |
| |
| <p>If the value passes its range check, it is padded with as many |
| trailing zero digits as necessary to meet the padding |
| argument.</p> |
| |
| <p>A <code>TYPE_NUMERIC</code> value buffer can conveniently be |
| interpreted with the C library function <code>atof(3)</code>.</p> |
| |
| <h3><a name="ftype_regexp" id="ftype_regexp">TYPE_REGEXP</a></h3> |
| |
| <p>This field type accepts data matching a regular expression. It |
| is set up as follows:</p> |
| |
| <pre> |
| int set_field_type(FIELD *field, /* field to alter */ |
| TYPE_REGEXP, /* type to associate */ |
| char *regexp); /* expression to match */ |
| </pre> |
| |
| <p>The syntax for regular expressions is that of |
| <code>regcomp(3)</code>. The check for regular-expression match |
| is performed on exit.</p> |
| |
| <h2><a name="fbuffer" id="fbuffer">Direct Field Buffer |
| Manipulation</a></h2> |
| |
| <p>The chief attribute of a field is its buffer contents. When a |
| form has been completed, your application usually needs to know |
| the state of each field buffer. You can find this out with:</p> |
| |
| <pre> |
| char *field_buffer(FIELD *field, /* field to query */ |
| int bufindex); /* number of buffer to query */ |
| </pre> |
| |
| <p>Normally, the state of the zero-numbered buffer for each field |
| is set by the user's editing actions on that field. It is |
| sometimes useful to be able to set the value of the zero-numbered |
| (or some other) buffer from your application:</p> |
| |
| <pre> |
| int set_field_buffer(FIELD *field, /* field to alter */ |
| int bufindex, /* number of buffer to alter */ |
| char *value); /* string value to set */ |
| </pre> |
| |
| <p>If the field is not large enough and cannot be resized to a |
| sufficiently large size to contain the specified value, the value |
| will be truncated to fit.</p> |
| |
| <p>Calling <code>field_buffer()</code> with a null field pointer |
| will raise an error. Calling <code>field_buffer()</code> on a |
| field not currently selected for input will return a correct |
| value. Calling <code>field_buffer()</code> on a field that is |
| currently selected for input may not necessarily give a correct |
| field buffer value, because entered data is not necessarily |
| copied to buffer zero before the exit validation check. To |
| guarantee that the returned buffer value reflects on-screen |
| reality, call <code>field_buffer()</code> either (1) in the |
| field's exit validation check routine, (2) from the field's or |
| form's initialization or termination hooks, or (3) just after a |
| <code>REQ_VALIDATION</code> request has been processed by the |
| forms driver.</p> |
| |
| <h2><a name="formattrs" id="formattrs">Attributes of Forms</a></h2> |
| |
| <p>As with field attributes, form attributes inherit a default |
| from a system default form structure. These defaults can be |
| queried or set by of these functions using a form-pointer |
| argument of <code>NULL</code>.</p> |
| |
| <p>The principal attribute of a form is its field list. You can |
| query and change this list with:</p> |
| |
| <pre> |
| int set_form_fields(FORM *form, /* form to alter */ |
| FIELD **fields); /* fields to connect */ |
| |
| char *form_fields(FORM *form); /* fetch fields of form */ |
| |
| int field_count(FORM *form); /* count connect fields */ |
| </pre> |
| |
| <p>The second argument of <code>set_form_fields()</code> may be a |
| NULL-terminated field pointer array like the one required by |
| <code>new_form()</code>. In that case, the old fields of the form |
| are disconnected but not freed (and eligible to be connected to |
| other forms), then the new fields are connected.</p> |
| |
| <p>It may also be null, in which case the old fields are |
| disconnected (and not freed) but no new ones are connected.</p> |
| |
| <p>The <code>field_count()</code> function simply counts the |
| number of fields connected to a given from. It returns -1 if the |
| form-pointer argument is NULL.</p> |
| |
| <h2><a name="fdisplay" id="fdisplay">Control of Form Display</a></h2> |
| |
| <p>In the overview section, you saw that to display a form you |
| normally start by defining its size (and fields), posting it, and |
| refreshing the screen. There is an hidden step before posting, |
| which is the association of the form with a frame window |
| (actually, a pair of windows) within which it will be displayed. |
| By default, the forms library associates every form with the |
| full-screen window <code>stdscr</code>.</p> |
| |
| <p>By making this step explicit, you can associate a form with a |
| declared frame window on your screen display. This can be useful |
| if you want to adapt the form display to different screen sizes, |
| dynamically tile forms on the screen, or use a form as part of an |
| interface layout managed by <a href="#panels">panels</a>.</p> |
| |
| <p>The two windows associated with each form have the same |
| functions as their analogues in the <a href="#menu">menu |
| library</a>. Both these windows are painted when the form is |
| posted and erased when the form is unposted.</p> |
| |
| <p>The outer or frame window is not otherwise touched by the form |
| routines. It exists so the programmer can associate a title, a |
| border, or perhaps help text with the form and have it properly |
| refreshed or erased at post/unpost time. The inner window or |
| subwindow is where the current form page is actually |
| displayed.</p> |
| |
| <p>In order to declare your own frame window for a form, you will |
| need to know the size of the form's bounding rectangle. You can |
| get this information with:</p> |
| |
| <pre> |
| int scale_form(FORM *form, /* form to query */ |
| int *rows, /* form rows */ |
| int *cols); /* form cols */ |
| </pre> |
| |
| <p>The form dimensions are passed back in the locations pointed |
| to by the arguments. Once you have this information, you can use |
| it to declare of windows, then use one of these functions:</p> |
| |
| <pre> |
| int set_form_win(FORM *form, /* form to alter */ |
| WINDOW *win); /* frame window to connect */ |
| |
| WINDOW *form_win(FORM *form); /* fetch frame window of form */ |
| |
| int set_form_sub(FORM *form, /* form to alter */ |
| WINDOW *win); /* form subwindow to connect */ |
| |
| WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */ |
| </pre> |
| |
| <p>Note that curses operations, including <code>refresh()</code>, |
| on the form, should be done on the frame window, not the form |
| subwindow.</p> |
| |
| <p>It is possible to check from your application whether all of a |
| scrollable field is actually displayed within the menu subwindow. |
| Use these functions:</p> |
| |
| <pre> |
| int data_ahead(FORM *form); /* form to be queried */ |
| |
| int data_behind(FORM *form); /* form to be queried */ |
| </pre> |
| |
| <p>The function <code>data_ahead()</code> returns TRUE if (a) the |
| current field is one-line and has undisplayed data off to the |
| right, (b) the current field is multi-line and there is data |
| off-screen below it.</p> |
| |
| <p>The function <code>data_behind()</code> returns TRUE if the |
| first (upper left hand) character position is off-screen (not |
| being displayed).</p> |
| |
| <p>Finally, there is a function to restore the form window's |
| cursor to the value expected by the forms driver:</p> |
| |
| <pre> |
| int pos_form_cursor(FORM *) /* form to be queried */ |
| </pre> |
| |
| <p>If your application changes the form window cursor, call this |
| function before handing control back to the forms driver in order |
| to re-synchronize it.</p> |
| |
| <h2><a name="fdriver" id="fdriver">Input Processing in the Forms |
| Driver</a></h2> |
| |
| <p>The function <code>form_driver()</code> handles virtualized |
| input requests for form navigation, editing, and validation |
| requests, just as <code>menu_driver</code> does for menus (see |
| the section on <a href="#minput">menu input handling</a>).</p> |
| |
| <pre> |
| int form_driver(FORM *form, /* form to pass input to */ |
| int request); /* form request code */ |
| </pre> |
| |
| <p>Your input virtualization function needs to take input and |
| then convert it to either an alphanumeric character (which is |
| treated as data to be entered in the currently-selected field), |
| or a forms processing request.</p> |
| |
| <p>The forms driver provides hooks (through input-validation and |
| field-termination functions) with which your application code can |
| check that the input taken by the driver matched what was |
| expected.</p> |
| |
| <h3><a name="fpage" id="fpage">Page Navigation Requests</a></h3> |
| |
| <p>These requests cause page-level moves through the form, |
| triggering display of a new form screen.</p> |
| |
| <dl> |
| <dt><code>REQ_NEXT_PAGE</code> |
| </dt> |
| |
| <dd>Move to the next form page.</dd> |
| |
| <dt><code>REQ_PREV_PAGE</code> |
| </dt> |
| |
| <dd>Move to the previous form page.</dd> |
| |
| <dt><code>REQ_FIRST_PAGE</code> |
| </dt> |
| |
| <dd>Move to the first form page.</dd> |
| |
| <dt><code>REQ_LAST_PAGE</code> |
| </dt> |
| |
| <dd>Move to the last form page.</dd> |
| </dl> |
| |
| <p>These requests treat the list as cyclic; that is, |
| <code>REQ_NEXT_PAGE</code> from the last page goes to the first, |
| and <code>REQ_PREV_PAGE</code> from the first page goes to the |
| last.</p> |
| |
| <h3><a name="ffield" id="ffield">Inter-Field Navigation |
| Requests</a></h3> |
| |
| <p>These requests handle navigation between fields on the same |
| page.</p> |
| |
| <dl> |
| <dt><code>REQ_NEXT_FIELD</code> |
| </dt> |
| |
| <dd>Move to next field.</dd> |
| |
| <dt><code>REQ_PREV_FIELD</code> |
| </dt> |
| |
| <dd>Move to previous field.</dd> |
| |
| <dt><code>REQ_FIRST_FIELD</code> |
| </dt> |
| |
| <dd>Move to the first field.</dd> |
| |
| <dt><code>REQ_LAST_FIELD</code> |
| </dt> |
| |
| <dd>Move to the last field.</dd> |
| |
| <dt><code>REQ_SNEXT_FIELD</code> |
| </dt> |
| |
| <dd>Move to sorted next field.</dd> |
| |
| <dt><code>REQ_SPREV_FIELD</code> |
| </dt> |
| |
| <dd>Move to sorted previous field.</dd> |
| |
| <dt><code>REQ_SFIRST_FIELD</code> |
| </dt> |
| |
| <dd>Move to the sorted first field.</dd> |
| |
| <dt><code>REQ_SLAST_FIELD</code> |
| </dt> |
| |
| <dd>Move to the sorted last field.</dd> |
| |
| <dt><code>REQ_LEFT_FIELD</code> |
| </dt> |
| |
| <dd>Move left to field.</dd> |
| |
| <dt><code>REQ_RIGHT_FIELD</code> |
| </dt> |
| |
| <dd>Move right to field.</dd> |
| |
| <dt><code>REQ_UP_FIELD</code> |
| </dt> |
| |
| <dd>Move up to field.</dd> |
| |
| <dt><code>REQ_DOWN_FIELD</code> |
| </dt> |
| |
| <dd>Move down to field.</dd> |
| </dl> |
| |
| <p>These requests treat the list of fields on a page as cyclic; |
| that is, <code>REQ_NEXT_FIELD</code> from the last field goes to |
| the first, and <code>REQ_PREV_FIELD</code> from the first field |
| goes to the last. The order of the fields for these (and the |
| <code>REQ_FIRST_FIELD</code> and <code>REQ_LAST_FIELD</code> |
| requests) is simply the order of the field pointers in the form |
| array (as set up by <code>new_form()</code> or |
| <code>set_form_fields()</code></p> |
| |
| <p>It is also possible to traverse the fields as if they had been |
| sorted in screen-position order, so the sequence goes |
| left-to-right and top-to-bottom. To do this, use the second group |
| of four sorted-movement requests.</p> |
| |
| <p>Finally, it is possible to move between fields using visual |
| directions up, down, right, and left. To accomplish this, use the |
| third group of four requests. Note, however, that the position of |
| a form for purposes of these requests is its upper-left |
| corner.</p> |
| |
| <p>For example, suppose you have a multi-line field B, and two |
| single-line fields A and C on the same line with B, with A to the |
| left of B and C to the right of B. A <code>REQ_MOVE_RIGHT</code> |
| from A will go to B only if A, B, and C <em>all</em> share the |
| same first line; otherwise it will skip over B to C.</p> |
| |
| <h3><a name="fifield" id="fifield">Intra-Field Navigation |
| Requests</a></h3> |
| |
| <p>These requests drive movement of the edit cursor within the |
| currently selected field.</p> |
| |
| <dl> |
| <dt><code>REQ_NEXT_CHAR</code> |
| </dt> |
| |
| <dd>Move to next character.</dd> |
| |
| <dt><code>REQ_PREV_CHAR</code> |
| </dt> |
| |
| <dd>Move to previous character.</dd> |
| |
| <dt><code>REQ_NEXT_LINE</code> |
| </dt> |
| |
| <dd>Move to next line.</dd> |
| |
| <dt><code>REQ_PREV_LINE</code> |
| </dt> |
| |
| <dd>Move to previous line.</dd> |
| |
| <dt><code>REQ_NEXT_WORD</code> |
| </dt> |
| |
| <dd>Move to next word.</dd> |
| |
| <dt><code>REQ_PREV_WORD</code> |
| </dt> |
| |
| <dd>Move to previous word.</dd> |
| |
| <dt><code>REQ_BEG_FIELD</code> |
| </dt> |
| |
| <dd>Move to beginning of field.</dd> |
| |
| <dt><code>REQ_END_FIELD</code> |
| </dt> |
| |
| <dd>Move to end of field.</dd> |
| |
| <dt><code>REQ_BEG_LINE</code> |
| </dt> |
| |
| <dd>Move to beginning of line.</dd> |
| |
| <dt><code>REQ_END_LINE</code> |
| </dt> |
| |
| <dd>Move to end of line.</dd> |
| |
| <dt><code>REQ_LEFT_CHAR</code> |
| </dt> |
| |
| <dd>Move left in field.</dd> |
| |
| <dt><code>REQ_RIGHT_CHAR</code> |
| </dt> |
| |
| <dd>Move right in field.</dd> |
| |
| <dt><code>REQ_UP_CHAR</code> |
| </dt> |
| |
| <dd>Move up in field.</dd> |
| |
| <dt><code>REQ_DOWN_CHAR</code> |
| </dt> |
| |
| <dd>Move down in field.</dd> |
| </dl> |
| |
| <p>Each <em>word</em> is separated from the previous and next |
| characters by whitespace. The commands to move to beginning and |
| end of line or field look for the first or last non-pad character |
| in their ranges.</p> |
| |
| <h3><a name="fscroll" id="fscroll">Scrolling Requests</a></h3> |
| |
| <p>Fields that are dynamic and have grown and fields explicitly |
| created with offscreen rows are scrollable. One-line fields |
| scroll horizontally; multi-line fields scroll vertically. Most |
| scrolling is triggered by editing and intra-field movement (the |
| library scrolls the field to keep the cursor visible). It is |
| possible to explicitly request scrolling with the following |
| requests:</p> |
| |
| <dl> |
| <dt><code>REQ_SCR_FLINE</code> |
| </dt> |
| |
| <dd>Scroll vertically forward a line.</dd> |
| |
| <dt><code>REQ_SCR_BLINE</code> |
| </dt> |
| |
| <dd>Scroll vertically backward a line.</dd> |
| |
| <dt><code>REQ_SCR_FPAGE</code> |
| </dt> |
| |
| <dd>Scroll vertically forward a page.</dd> |
| |
| <dt><code>REQ_SCR_BPAGE</code> |
| </dt> |
| |
| <dd>Scroll vertically backward a page.</dd> |
| |
| <dt><code>REQ_SCR_FHPAGE</code> |
| </dt> |
| |
| <dd>Scroll vertically forward half a page.</dd> |
| |
| <dt><code>REQ_SCR_BHPAGE</code> |
| </dt> |
| |
| <dd>Scroll vertically backward half a page.</dd> |
| |
| <dt><code>REQ_SCR_FCHAR</code> |
| </dt> |
| |
| <dd>Scroll horizontally forward a character.</dd> |
| |
| <dt><code>REQ_SCR_BCHAR</code> |
| </dt> |
| |
| <dd>Scroll horizontally backward a character.</dd> |
| |
| <dt><code>REQ_SCR_HFLINE</code> |
| </dt> |
| |
| <dd>Scroll horizontally one field width forward.</dd> |
| |
| <dt><code>REQ_SCR_HBLINE</code> |
| </dt> |
| |
| <dd>Scroll horizontally one field width backward.</dd> |
| |
| <dt><code>REQ_SCR_HFHALF</code> |
| </dt> |
| |
| <dd>Scroll horizontally one half field width forward.</dd> |
| |
| <dt><code>REQ_SCR_HBHALF</code> |
| </dt> |
| |
| <dd>Scroll horizontally one half field width backward.</dd> |
| </dl> |
| |
| <p>For scrolling purposes, a <em>page</em> of a field is the |
| height of its visible part.</p> |
| |
| <h3><a name="fedit" id="fedit">Editing Requests</a></h3> |
| |
| <p>When you pass the forms driver an ASCII character, it is |
| treated as a request to add the character to the field's data |
| buffer. Whether this is an insertion or a replacement depends on |
| the field's edit mode (insertion is the default.</p> |
| |
| <p>The following requests support editing the field and changing |
| the edit mode:</p> |
| |
| <dl> |
| <dt><code>REQ_INS_MODE</code> |
| </dt> |
| |
| <dd>Set insertion mode.</dd> |
| |
| <dt><code>REQ_OVL_MODE</code> |
| </dt> |
| |
| <dd>Set overlay mode.</dd> |
| |
| <dt><code>REQ_NEW_LINE</code> |
| </dt> |
| |
| <dd>New line request (see below for explanation).</dd> |
| |
| <dt><code>REQ_INS_CHAR</code> |
| </dt> |
| |
| <dd>Insert space at character location.</dd> |
| |
| <dt><code>REQ_INS_LINE</code> |
| </dt> |
| |
| <dd>Insert blank line at character location.</dd> |
| |
| <dt><code>REQ_DEL_CHAR</code> |
| </dt> |
| |
| <dd>Delete character at cursor.</dd> |
| |
| <dt><code>REQ_DEL_PREV</code> |
| </dt> |
| |
| <dd>Delete previous word at cursor.</dd> |
| |
| <dt><code>REQ_DEL_LINE</code> |
| </dt> |
| |
| <dd>Delete line at cursor.</dd> |
| |
| <dt><code>REQ_DEL_WORD</code> |
| </dt> |
| |
| <dd>Delete word at cursor.</dd> |
| |
| <dt><code>REQ_CLR_EOL</code> |
| </dt> |
| |
| <dd>Clear to end of line.</dd> |
| |
| <dt><code>REQ_CLR_EOF</code> |
| </dt> |
| |
| <dd>Clear to end of field.</dd> |
| |
| <dt><code>REQ_CLEAR_FIELD</code> |
| </dt> |
| |
| <dd>Clear entire field.</dd> |
| </dl> |
| |
| <p>The behavior of the <code>REQ_NEW_LINE</code> and |
| <code>REQ_DEL_PREV</code> requests is complicated and partly |
| controlled by a pair of forms options. The special cases are |
| triggered when the cursor is at the beginning of a field, or on |
| the last line of the field.</p> |
| |
| <p>First, we consider <code>REQ_NEW_LINE</code>:</p> |
| |
| <p>The normal behavior of <code>REQ_NEW_LINE</code> in insert |
| mode is to break the current line at the position of the edit |
| cursor, inserting the portion of the current line after the |
| cursor as a new line following the current and moving the cursor |
| to the beginning of that new line (you may think of this as |
| inserting a newline in the field buffer).</p> |
| |
| <p>The normal behavior of <code>REQ_NEW_LINE</code> in overlay |
| mode is to clear the current line from the position of the edit |
| cursor to end of line. The cursor is then moved to the beginning |
| of the next line.</p> |
| |
| <p>However, <code>REQ_NEW_LINE</code> at the beginning of a |
| field, or on the last line of a field, instead does a |
| <code>REQ_NEXT_FIELD</code>. <code>O_NL_OVERLOAD</code> option is |
| off, this special action is disabled.</p> |
| |
| <p>Now, let us consider <code>REQ_DEL_PREV</code>:</p> |
| |
| <p>The normal behavior of <code>REQ_DEL_PREV</code> is to delete |
| the previous character. If insert mode is on, and the cursor is |
| at the start of a line, and the text on that line will fit on the |
| previous one, it instead appends the contents of the current line |
| to the previous one and deletes the current line (you may think |
| of this as deleting a newline from the field buffer).</p> |
| |
| <p>However, <code>REQ_DEL_PREV</code> at the beginning of a field |
| is instead treated as a <code>REQ_PREV_FIELD</code>.</p> |
| |
| <p>If the <code>O_BS_OVERLOAD</code> option is off, this special |
| action is disabled and the forms driver just returns |
| <code>E_REQUEST_DENIED</code>.</p> |
| |
| <p>See <a href="#frmoptions">Form Options</a> for discussion of |
| how to set and clear the overload options.</p> |
| |
| <h3><a name="forder" id="forder">Order Requests</a></h3> |
| |
| <p>If the type of your field is ordered, and has associated |
| functions for getting the next and previous values of the type |
| from a given value, there are requests that can fetch that value |
| into the field buffer:</p> |
| |
| <dl> |
| <dt><code>REQ_NEXT_CHOICE</code> |
| </dt> |
| |
| <dd>Place the successor value of the current value in the |
| buffer.</dd> |
| |
| <dt><code>REQ_PREV_CHOICE</code> |
| </dt> |
| |
| <dd>Place the predecessor value of the current value in the |
| buffer.</dd> |
| </dl> |
| |
| <p>Of the built-in field types, only <code>TYPE_ENUM</code> has |
| built-in successor and predecessor functions. When you define a |
| field type of your own (see <a href="#fcustom">Custom Validation |
| Types</a>), you can associate our own ordering functions.</p> |
| |
| <h3><a name="fappcmds" id="fappcmds">Application Commands</a></h3> |
| |
| <p>Form requests are represented as integers above the |
| <code>curses</code> value greater than <code>KEY_MAX</code> and |
| less than or equal to the constant <code>MAX_COMMAND</code>. If |
| your input-virtualization routine returns a value above |
| <code>MAX_COMMAND</code>, the forms driver will ignore it.</p> |
| |
| <h2><a name="fhooks" id="fhooks">Field Change Hooks</a></h2> |
| |
| <p>It is possible to set function hooks to be executed whenever |
| the current field or form changes. Here are the functions that |
| support this:</p> |
| |
| <pre> |
| typedef void (*HOOK)(); /* pointer to function returning void */ |
| |
| int set_form_init(FORM *form, /* form to alter */ |
| HOOK hook); /* initialization hook */ |
| |
| HOOK form_init(FORM *form); /* form to query */ |
| |
| int set_form_term(FORM *form, /* form to alter */ |
| HOOK hook); /* termination hook */ |
| |
| HOOK form_term(FORM *form); /* form to query */ |
| |
| int set_field_init(FORM *form, /* form to alter */ |
| HOOK hook); /* initialization hook */ |
| |
| HOOK field_init(FORM *form); /* form to query */ |
| |
| int set_field_term(FORM *form, /* form to alter */ |
| HOOK hook); /* termination hook */ |
| |
| HOOK field_term(FORM *form); /* form to query */ |
| </pre> |
| |
| <p>These functions allow you to either set or query four |
| different hooks. In each of the set functions, the second |
| argument should be the address of a hook function. These |
| functions differ only in the timing of the hook call.</p> |
| |
| <dl> |
| <dt>form_init</dt> |
| |
| <dd>This hook is called when the form is posted; also, just |
| after each page change operation.</dd> |
| |
| <dt>field_init</dt> |
| |
| <dd>This hook is called when the form is posted; also, just |
| after each field change</dd> |
| |
| <dt>field_term</dt> |
| |
| <dd>This hook is called just after field validation; that is, |
| just before the field is altered. It is also called when the |
| form is unposted.</dd> |
| |
| <dt>form_term</dt> |
| |
| <dd>This hook is called when the form is unposted; also, just |
| before each page change operation.</dd> |
| </dl> |
| |
| <p>Calls to these hooks may be triggered</p> |
| |
| <ol> |
| <li>When user editing requests are processed by the forms |
| driver</li> |
| |
| <li>When the current page is changed by |
| <code>set_current_field()</code> call</li> |
| |
| <li>When the current field is changed by a |
| <code>set_form_page()</code> call</li> |
| </ol> |
| |
| <p>See <a name="ffocus" id="ffocus">Field Change Commands</a> for |
| discussion of the latter two cases.</p> |
| |
| <p>You can set a default hook for all fields by passing one of |
| the set functions a NULL first argument.</p> |
| |
| <p>You can disable any of these hooks by (re)setting them to |
| NULL, the default value.</p> |
| |
| <h2><a href="#ffocus">Field Change Commands</a></h2> |
| |
| <p>Normally, navigation through the form will be driven by the |
| user's input requests. But sometimes it is useful to be able to |
| move the focus for editing and viewing under control of your |
| application, or ask which field it currently is in. The following |
| functions help you accomplish this:</p> |
| |
| <pre> |
| int set_current_field(FORM *form, /* form to alter */ |
| FIELD *field); /* field to shift to */ |
| |
| FIELD *current_field(FORM *form); /* form to query */ |
| |
| int field_index(FORM *form, /* form to query */ |
| FIELD *field); /* field to get index of */ |
| </pre> |
| |
| <p>The function <code>field_index()</code> returns the index of |
| the given field in the given form's field array (the array passed |
| to <code>new_form()</code> or |
| <code>set_form_fields()</code>).</p> |
| |
| <p>The initial current field of a form is the first active field |
| on the first page. The function <code>set_form_fields()</code> |
| resets this.</p> |
| |
| <p>It is also possible to move around by pages.</p> |
| |
| <pre> |
| int set_form_page(FORM *form, /* form to alter */ |
| int page); /* page to go to (0-origin) */ |
| |
| int form_page(FORM *form); /* return form's current page */ |
| </pre> |
| |
| <p>The initial page of a newly-created form is 0. The function |
| <code>set_form_fields()</code> resets this.</p> |
| |
| <h2><a name="frmoptions" id="frmoptions">Form Options</a></h2> |
| |
| <p>Like fields, forms may have control option bits. They can be |
| changed or queried with these functions:</p> |
| |
| <pre> |
| int set_form_opts(FORM *form, /* form to alter */ |
| int attr); /* attribute to set */ |
| |
| int form_opts_on(FORM *form, /* form to alter */ |
| int attr); /* attributes to turn on */ |
| |
| int form_opts_off(FORM *form, /* form to alter */ |
| int attr); /* attributes to turn off */ |
| |
| int form_opts(FORM *form); /* form to query */ |
| </pre> |
| |
| <p>By default, all options are on. Here are the available option |
| bits:</p> |
| |
| <dl> |
| <dt>O_NL_OVERLOAD</dt> |
| |
| <dd>Enable overloading of <code>REQ_NEW_LINE</code> as |
| described in <a href="#fedit">Editing Requests</a>. The value |
| of this option is ignored on dynamic fields that have not |
| reached their size limit; these have no last line, so the |
| circumstances for triggering a <code>REQ_NEXT_FIELD</code> |
| never arise.</dd> |
| |
| <dt>O_BS_OVERLOAD</dt> |
| |
| <dd>Enable overloading of <code>REQ_DEL_PREV</code> as |
| described in <a href="#fedit">Editing Requests</a>.</dd> |
| </dl> |
| |
| <p>The option values are bit-masks and can be composed with |
| logical-or in the obvious way.</p> |
| |
| <h2><a name="fcustom" id="fcustom">Custom Validation Types</a></h2> |
| |
| <p>The <code>form</code> library gives you the capability to |
| define custom validation types of your own. Further, the optional |
| additional arguments of <code>set_field_type</code> effectively |
| allow you to parameterize validation types. Most of the |
| complications in the validation-type interface have to do with |
| the handling of the additional arguments within custom validation |
| functions.</p> |
| |
| <h3><a name="flinktypes" id="flinktypes">Union Types</a></h3> |
| |
| <p>The simplest way to create a custom data type is to compose it |
| from two preexisting ones:</p> |
| |
| <pre> |
| FIELD *link_fieldtype(FIELDTYPE *type1, |
| FIELDTYPE *type2); |
| </pre> |
| |
| <p>This function creates a field type that will accept any of the |
| values legal for either of its argument field types (which may be |
| either predefined or programmer-defined). If a |
| <code>set_field_type()</code> call later requires arguments, the |
| new composite type expects all arguments for the first type, than |
| all arguments for the second. Order functions (see <a href= |
| "#forder">Order Requests</a>) associated with the component types |
| will work on the composite; what it does is check the validation |
| function for the first type, then for the second, to figure what |
| type the buffer contents should be treated as.</p> |
| |
| <h3><a name="fnewtypes" id="fnewtypes">New Field Types</a></h3> |
| |
| <p>To create a field type from scratch, you need to specify one |
| or both of the following things:</p> |
| |
| <ul> |
| <li>A character-validation function, to check each character as |
| it is entered.</li> |
| |
| <li>A field-validation function to be applied on exit from the |
| field.</li> |
| </ul> |
| |
| <p>Here is how you do that:</p> |
| |
| <pre> |
| typedef int (*HOOK)(); /* pointer to function returning int */ |
| |
| FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */ |
| HOOK c_validate) /* character validator */ |
| |
| int free_fieldtype(FIELDTYPE *ftype); /* type to free */ |
| </pre> |
| |
| <p>At least one of the arguments of <code>new_fieldtype()</code> |
| must be non-NULL. The forms driver will automatically call the |
| new type's validation functions at appropriate points in |
| processing a field of the new type.</p> |
| |
| <p>The function <code>free_fieldtype()</code> deallocates the |
| argument fieldtype, freeing all storage associated with it.</p> |
| |
| <p>Normally, a field validator is called when the user attempts |
| to leave the field. Its first argument is a field pointer, from |
| which it can get to field buffer 0 and test it. If the function |
| returns TRUE, the operation succeeds; if it returns FALSE, the |
| edit cursor stays in the field.</p> |
| |
| <p>A character validator gets the character passed in as a first |
| argument. It too should return TRUE if the character is valid, |
| FALSE otherwise.</p> |
| |
| <h3><a name="fcheckargs" id="fcheckargs">Validation Function |
| Arguments</a></h3> |
| |
| <p>Your field- and character- validation functions will be passed |
| a second argument as well. This second argument is the address of |
| a structure (which we will call a <em>pile</em>) built from any |
| of the field-type-specific arguments passed to |
| <code>set_field_type()</code>. If no such arguments are defined |
| for the field type, this pile pointer argument will be NULL.</p> |
| |
| <p>In order to arrange for such arguments to be passed to your |
| validation functions, you must associate a small set of |
| storage-management functions with the type. The forms driver will |
| use these to synthesize a pile from the trailing arguments of |
| each <code>set_field_type()</code> argument, and a pointer to the |
| pile will be passed to the validation functions.</p> |
| |
| <p>Here is how you make the association:</p> |
| |
| <pre> |
| typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */ |
| typedef void (*VOIDHOOK)(); /* pointer to function returning void */ |
| |
| int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ |
| PTRHOOK make_str, /* make structure from args */ |
| PTRHOOK copy_str, /* make copy of structure */ |
| VOIDHOOK free_str); /* free structure storage */ |
| </pre> |
| |
| <p>Here is how the storage-management hooks are used:</p> |
| |
| <dl> |
| <dt><code>make_str</code> |
| </dt> |
| |
| <dd>This function is called by <code>set_field_type()</code>. |
| It gets one argument, a <code>va_list</code> of the |
| type-specific arguments passed to |
| <code>set_field_type()</code>. It is expected to return a pile |
| pointer to a data structure that encapsulates those |
| arguments.</dd> |
| |
| <dt><code>copy_str</code> |
| </dt> |
| |
| <dd>This function is called by form library functions that |
| allocate new field instances. It is expected to take a pile |
| pointer, copy the pile to allocated storage, and return the |
| address of the pile copy.</dd> |
| |
| <dt><code>free_str</code> |
| </dt> |
| |
| <dd>This function is called by field- and type-deallocation |
| routines in the library. It takes a pile pointer argument, and |
| is expected to free the storage of that pile.</dd> |
| </dl> |
| |
| <p>The <code>make_str</code> and <code>copy_str</code> functions |
| may return NULL to signal allocation failure. The library |
| routines will that call them will return error indication when |
| this happens. Thus, your validation functions should never see a |
| NULL file pointer and need not check specially for it.</p> |
| |
| <h3><a name="fcustorder" id="fcustorder">Order Functions For |
| Custom Types</a></h3> |
| |
| <p>Some custom field types are simply ordered in the same |
| well-defined way that <code>TYPE_ENUM</code> is. For such types, |
| it is possible to define successor and predecessor functions to |
| support the <code>REQ_NEXT_CHOICE</code> and |
| <code>REQ_PREV_CHOICE</code> requests. Here is how:</p> |
| |
| <pre> |
| typedef int (*INTHOOK)(); /* pointer to function returning int */ |
| |
| int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ |
| INTHOOK succ, /* get successor value */ |
| INTHOOK pred); /* get predecessor value */ |
| </pre> |
| |
| <p>The successor and predecessor arguments will each be passed |
| two arguments; a field pointer, and a pile pointer (as for the |
| validation functions). They are expected to use the function |
| <code>field_buffer()</code> to read the current value, and |
| <code>set_field_buffer()</code> on buffer 0 to set the next or |
| previous value. Either hook may return TRUE to indicate success |
| (a legal next or previous value was set) or FALSE to indicate |
| failure.</p> |
| |
| <h3><a name="fcustprobs" id="fcustprobs">Avoiding Problems</a></h3> |
| |
| <p>The interface for defining custom types is complicated and |
| tricky. Rather than attempting to create a custom type entirely |
| from scratch, you should start by studying the library source |
| code for whichever of the pre-defined types seems to be closest |
| to what you want.</p> |
| |
| <p>Use that code as a model, and evolve it towards what you |
| really want. You will avoid many problems and annoyances that |
| way. The code in the <code>ncurses</code> library has been |
| specifically exempted from the package copyright to support |
| this.</p> |
| |
| <p>If your custom type defines order functions, have do something |
| intuitive with a blank field. A useful convention is to make the |
| successor of a blank field the types minimum value, and its |
| predecessor the maximum.</p> |
| </body> |
| </html> |