
/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */


#ifndef SkFontHost_DEFINED
#define SkFontHost_DEFINED

#include "SkTypeface.h"

class SkDescriptor;
class SkScalerContext;
struct SkScalerContextRec;
class SkStream;
class SkWStream;

/** \class SkFontHost

    This class is ported to each environment. It is responsible for bridging
    the gap between the (sort of) abstract class SkTypeface and the
    platform-specific implementation that provides access to font files.

    One basic task is for each create (subclass of) SkTypeface, the FontHost is
    responsible for assigning a uniqueID. The ID should be unique for the
    underlying font file/data, not unique per typeface instance. Thus it is
    possible/common to request a typeface for the same font more than once
    (e.g. asking for the same font by name several times). The FontHost may
    return seperate typeface instances in that case, or it may choose to use a
    cache and return the same instance (but calling typeface->ref(), since the
    caller is always responsible for calling unref() on each instance that is
    returned). Either way, the fontID for those instance(s) will be the same.
    In addition, the fontID should never be set to 0. That value is used as a
    sentinel to indicate no-font-id.

    The major aspects are:
    1) Given either a name/style, return a subclass of SkTypeface that
        references the closest matching font available on the host system.
    2) Given the data for a font (either in a stream or a file name), return
        a typeface that allows access to that data.
    3) Each typeface instance carries a 32bit ID for its corresponding font.
        SkFontHost turns that ID into a stream to access the font's data.
    4) Given a font ID, return a subclass of SkScalerContext, which connects a
        font scaler (e.g. freetype or other) to the font's data.
    5) Utilites to manage the font cache (budgeting) and gamma correction
*/
class SK_API SkFontHost {
public:
    /** LCDs either have their color elements arranged horizontally or
     vertically. When rendering subpixel glyphs we need to know which way
     round they are.

     Note, if you change this after startup, you'll need to flush the glyph
     cache because it'll have the wrong type of masks cached.

     @deprecated use SkPixelGeometry instead.
     */
    enum LCDOrientation {
        kHorizontal_LCDOrientation = 0,    //!< this is the default
        kVertical_LCDOrientation   = 1
    };

    /** @deprecated set on Device creation. */
    static void SetSubpixelOrientation(LCDOrientation orientation);
    /** @deprecated get from Device. */
    static LCDOrientation GetSubpixelOrientation();

    /** LCD color elements can vary in order. For subpixel text we need to know
     the order which the LCDs uses so that the color fringes are in the
     correct place.

     Note, if you change this after startup, you'll need to flush the glyph
     cache because it'll have the wrong type of masks cached.

     kNONE_LCDOrder means that the subpixel elements are not spatially
     separated in any usable fashion.

     @deprecated use SkPixelGeometry instead.
     */
    enum LCDOrder {
        kRGB_LCDOrder = 0,    //!< this is the default
        kBGR_LCDOrder = 1,
        kNONE_LCDOrder = 2
    };

    /** @deprecated set on Device creation. */
    static void SetSubpixelOrder(LCDOrder order);
    /** @deprecated get from Device. */
    static LCDOrder GetSubpixelOrder();

    /** If Skia is running in a constrained environment and the typeface
     implementation is handle based, the typeface data may become
     unavailable asynchronously. If a font host or scaler context method is
     unable to access font data, it may call this function as a request to
     make the handle contained in the typeface useable.
     */
    static void EnsureTypefaceAccessible(const SkTypeface& typeface);

    /**
     *  DEPRECATED -- will be DESTROYED
     *
     *  Given a "current" fontID, return a ref to the next logical typeface
     *  when searching fonts for a given unicode value. Typically the caller
     *  will query a given font, and if a unicode value is not supported, they
     *  will call this, and if 0 is not returned, will search that font, and so
     *  on. This process must be finite, and when the fonthost sees a
     *  font with no logical successor, it must return NULL.
     *
     *  The original fontID is also provided. This is the initial font that was
     *  stored in the typeface of the caller. It is provided as an aid to choose
     *  the best next logical font. e.g. If the original font was bold or serif,
     *  but the 2nd in the logical chain was plain, then a subsequent call to
     *  get the 3rd can still inspect the original, and try to match its
     *  stylistic attributes.
     */
    static SkTypeface* NextLogicalTypeface(SkFontID currFontID, SkFontID origFontID);


    ///// public HACK FOR FREETYPE -- will be fixed

    /** Return a new stream to read the font data, or null if the uniqueID does
     not match an existing typeface. .The caller must call stream->unref()
     when it is finished reading the data.
     */
    static SkStream* OpenStream(SkFontID uniqueID);

    /** Some fonts are stored in files. If that is true for the fontID, then
     this returns the byte length of the full file path. If path is not null,
     then the full path is copied into path (allocated by the caller), up to
     length bytes. If index is not null, then it is set to the truetype
     collection index for this font, or 0 if the font is not in a collection.

     Note: GetFileName does not assume that path is a null-terminated string,
     so when it succeeds, it only copies the bytes of the file name and
     nothing else (i.e. it copies exactly the number of bytes returned by the
     function. If the caller wants to treat path[] as a C string, it must be
     sure that it is allocated at least 1 byte larger than the returned size,
     and it must copy in the terminating 0.

     If the fontID does not correspond to a file, then the function returns
     0, and the path and index parameters are ignored.

     @param fontID   The font whose file name is being queried
     @param path     Either NULL, or storage for receiving up to length bytes
     of the font's file name. Allocated by the caller.
     @param length   The maximum space allocated in path (by the caller).
     Ignored if path is NULL.
     @param index    Either NULL, or receives the TTC index for this font.
     If the font is not a TTC, then will be set to 0.
     @return The byte length of th font's file name, or 0 if the font is not
     baked by a file.
     */
    static size_t GetFileName(SkFontID fontID, char path[], size_t length,
                              int32_t* index);

    // END_HACK for freetype

private:
    /** Return a new, closest matching typeface given either an existing family
        (specified by a typeface in that family) or by a familyName and a
        requested style.
        1) If familyFace is null, use familyName.
        2) If familyName is null, use data (UTF-16 to cover).
        3) If all are null, return the default font that best matches style
     */
    static SkTypeface* CreateTypeface(const SkTypeface* familyFace,
                                      const char familyName[],
                                      SkTypeface::Style style);

    /** Return a new typeface given the data buffer. If the data does not
        represent a valid font, returns null.

        If a typeface instance is returned, the caller is responsible for
        calling unref() on the typeface when they are finished with it.

        The returned typeface may or may not have called ref() on the stream
        parameter. If the typeface has not called ref(), then it may have made
        a copy of the releveant data. In either case, the caller is still
        responsible for its refcnt ownership of the stream.
     */
    static SkTypeface* CreateTypefaceFromStream(SkStream*);

    /** Return a new typeface from the specified file path. If the file does not
        represent a valid font, this returns null. If a typeface is returned,
        the caller is responsible for calling unref() when it is no longer used.
     */
    static SkTypeface* CreateTypefaceFromFile(const char path[]);

    ///////////////////////////////////////////////////////////////////////////

    /** Write a unique identifier to the stream, so that the same typeface can
        be retrieved with Deserialize(). The standard format is to serialize
        a SkFontDescriptor followed by a uint32_t length value. If the length
        is non-zero then the following bytes (of that length) represent a
        serialized copy of the font which can be recreated from a stream.
    */
    static void Serialize(const SkTypeface*, SkWStream*);

    /** Given a stream created by Serialize(), return a new typeface (like
        CreateTypeface) which is either an exact match to the one serialized
        or the best available typeface based on the data in the deserialized
        SkFontDescriptor.
     */
    static SkTypeface* Deserialize(SkStream*);

    ///////////////////////////////////////////////////////////////////////////

    /** Retrieve detailed typeface metrics.  Used by the PDF backend.
        @param perGlyphInfo Indicate what glyph specific information (advances,
                            names, etc.) should be populated.
        @return The returned object has already been referenced.  NULL is
                returned if the font is not found.
        @param glyphIDs  For per-glyph info, specify subset of the font by
                         giving glyph ids.  Each integer represents a glyph
                         id.  Passing NULL means all glyphs in the font.
        @param glyphIDsCount Number of elements in subsetGlyphIds. Ignored if
                             glyphIDs is NULL.
     */
    static SkAdvancedTypefaceMetrics* GetAdvancedTypefaceMetrics(
            SkFontID fontID,
            SkAdvancedTypefaceMetrics::PerGlyphInfo perGlyphInfo,
            const uint32_t* glyphIDs,
            uint32_t glyphIDsCount);

    ///////////////////////////////////////////////////////////////////////////

    friend class SkTypeface;
};

#endif