Android Emulator Skin File Specification:
=========================================

Revisions:
----------
    Revision 2. Dated 2009-12-07
    Dynamic Layout support added 10/2012

Introduction:
-------------

The Android emulator program is capable of displaying a window containing
an image of a fake handset and associated controls (e.g. D-Pad, trackball,
keyboard).

The content of this window is dictated by a "skin", i.e. a collection of
images and configuration data that indicates how to populate the window.
Each skin can have several "layouts" (e.g. "landscape" and "portrait")
corresponding to different orientation / physical configurations of the
emulated handset.

This document specifies how to generate a new skin for the emulator.
The emulator also supports dynamically creating the layout section of
the skin, thereby removing the necessity to create skins for each new
handset type. See the last section regarding info on dynamic controls.

General File Format:
--------------------

Each "skin" has a unique name and corresponds to a directory filled with
various files. All skins are located under a parent "skin-dir" directory.
You can use the '-skin-dir <path>' and '-skin <name>' options when starting
the emulator to specify them. This will instruct the program to look into

    <path>/<name>/

For skin-specific files. Without these options, the emulator will look for
skins in the SDK in a way described later in this document.

The most important file in a skin must be named 'layout', as in:

   <path>/<name>/layout

The format of this file must follow the "aconfig" specification, see
docs/ANDROID-CONFIG-FILES.TXT for details about it.


Layouts & Parts:
----------------

Each skin file must define a list of 'parts' and a list of 'layouts'.

A 'skin part' correspond to a named item that can contain a set of
visual/control elements that can be of the following types:

 - 'background': A background image in PNG format.

 - 'display': An emulated LCD screen area.

 - 'buttons': A set of clickable control areas (e.g. for a D-Pad, or
              a Keyboard)

Each part can be independently positioned and/or rotated in a 'layout'.
A 'skin layout' is simply a specific arrangement of parts. A typical device
skin file contains two layouts: one for landscape mode, and another one for
portrait mode. More layouts can be used if needed. For example, one could
use portrait + landscape-with-keyboard-closed + landscape-with-keyboard-opened)


Skin Layouts:
-------------

Each skin layout is a named sub-key of the top-level 'layouts' key in the
config file, for example:

    layouts {
        portrait {
            ....
        }
        landscape {
            ....
        }
    }

Defines two layouts named 'portrait' and 'landscape'.

Each layout can have the following keys (and corresponding values):

- 'width': The width of the emulator window in pixels, as an integer

- 'height': The height of the emulator window in pixels, as an integer

- 'color' : Background color to be used to fill the emulator window.
            this is a 32-bit ARGB value, the 0x prefix can be used to
            use hexadecimal notation.

- 'event' : An optional specific Linux event code that is generated whenever
            the emulator switches/initializes this layout. This is used to
            emulate the 'keyboard-lid open/close' events when emulating
            certain devices with a hardware keyboard.

            The value must be of the format:

                 <type>:<code>:<value>

            Where the event type, code and value are numerical values or,
            in certain cases string aliases for Linux input-subsystem event
            codes. You can use the following emulator console commands to
            print valid types and codes:

                event types         -> prints all valid types
                event codes <type>  -> prints all valid codes for <type>

            The typical event to be used is EV_SW:0:1 for portrait mode
            and EV_SW:0:0 for landscape ones. They corresponds to "keyboard
            closed" and "keyboard opened" respectively, and would match a
            device like the T-Mobile G1 or the Verizon Droid.

- 'onion' : Specifies an image to overlay on the display. Each such key may
            contain the following sub-keys:
            - 'image' [required]: Filename of image to overlay
            - 'alpha' [optional]: How opaque the image should be, from 0 (not
              visible at all) to 100 (fully opaque). Default is 50.
            - 'rotation' [optional]: Integer in the 0..3 range, specifying the
              rotation of the image in 90-degree increments.

- 'part<n>': Individual part references for the layout. They are named
             in incremental numerical order, starting from 'part1', as in
             'part1', 'part2', 'part3', etc...

             Each such key must contain the following sub-keys:

               - 'name': The name of the corresponding part to be displayed
                         as defined in the rest of the configuration file

               - 'x':  Horizontal offset where the part is displayed
               - 'y':  Vertical offset where the part is displayed

               - 'rotation': An optional sub-key which value is a integer
                             in the 0..3 range specifying the rotation
                             (in 90-degrees increment) to apply to the part
                             before display. 

- 'dpad-rotation': 
             An option integer in the 0..3 range indicating which
             counter-rotation (in 90-degrees increments) to apply to the
             D-Pad keys for proper usage.

             This is needed because the Android framework considers that
             the DPad is in landscape mode when the device is in landscape
             mode and will-auto-rotate the D-Pad value. This setting is used
             to counter-effect this correction for certain skins which
             do not rotate the DPad in landscape mode.


Skin Parts:
-----------

Each skin part is a sub-key of the top-level 'parts' key in the configuration
file. For example:

    parts {
        foo {
            ...
        }
        bar {
            ...
        }
        zoo {
            ...
        }
    }

Defines three parts named 'foo', 'bar' and 'zoo'.

Each part can have one or more elements of the following type/key name that
will determine its visual appearance:

- 'background':
        A background image in PNG format. This is a tree key that can
        have the following sub-keys:

            - 'image':  Name of the PNG image in the skin directory
            - 'x'    :  Optional horizontal offset in pixels (integer)
            - 'y'    :  Optional vertical offset in pixels (integer)

- 'display':
        An optional rectangular area that will appear on top of the
        background image to display an emulated LCD screen. Valid sub-keys
        are:

            - 'x'       : Optional horizontal offset in pixels (integer)
            - 'y'       : Optional vertical offset in pixels (integer)
            - 'width'   : Width in pixels (integer)
            - 'height'  : Height in pixels (integer)
            - 'rotation': Optional rotation value (0..3) in 90 degrees
                          increments.

- 'buttons':
        Used to define a list of rectangular clickable control areas with
        an optional high-lighting image. Each sub-key must have a unique
        name, and may contain the following sub-sub-keys:

            - 'x'       : Horizontal offset in pixels (integer)
            - 'y'       : Vertical offset in pixels (integer)
            - 'image'   : PNG image of the high-lighting for the button

        Each highlight image will be drawn on top of the background are for
        the button. A typical one has 50% opacity. The highlight will be drawn
        twice to simulate 'clicked' state.

        The image's dimensions are used to determine the size of the control
        area.

        The name of each button must correspond to the list of key symbols
        defined in the _keyinfo_table array defined in android/skin/file.c.

Other top-level keys:
---------------------

A few other top-level keys are supported for legacy reasons, but the
corresponding definition is best defined in the hardware properties/config
file instead:

- 'keyboard.charmap':
    Optional, must be the name of the charmap being used for this
    skin. Currently unused so ignore this.

- 'network.speed':
    Default network speed for this skin. Values correspond to the
    -netspeed <speed> emulator command-line option.

- 'network.delay':
    Default network latency for this skin. Values correspond to the
    -netdelay <delay> emulator command-line option.

Dynamic Layouts:
----------------

The emulator also supports a skin that is dynamically generated. This
skin (present in folder "dynamic" in the skins folder) follows the same
format as other skins, except that it only defines the list of parts/controls
that can be used in the skin. The layouts section is generated at
runtime by the emulator. The parts section describes all the controls that
can be used in any handset. All these parts have both an enabled and a
disabled version defined in the skin, and at runtime the emulator reads
the hardware definition and decides which of those two controls to actually
use.