ref: 38b349c41b2456d533cf60fb966a32d1a665dc8f
dir: /include/freetype/ftcache.h/
/****************************************************************************
*
* ftcache.h
*
* FreeType Cache subsystem (specification).
*
* Copyright (C) 1996-2021 by
* David Turner, Robert Wilhelm, and Werner Lemberg.
*
* This file is part of the FreeType project, and may only be used,
* modified, and distributed under the terms of the FreeType project
* license, LICENSE.TXT. By continuing to use, modify, or distribute
* this file you indicate that you have read the license and
* understand and accept it fully.
*
*/
#ifndef FTCACHE_H_
#define FTCACHE_H_
#include <freetype/ftglyph.h>
FT_BEGIN_HEADER
/**************************************************************************
*
* @section:
* cache_subsystem
*
* @title:
* Cache Sub-System
*
* @abstract:
* How to cache face, size, and glyph data with FreeType~2.
*
* @description:
* This section describes the FreeType~2 cache sub-system, which is used
* to limit the number of concurrently opened @FT_Face and @FT_Size
* objects, as well as caching information like character maps and glyph
* images while limiting their maximum memory usage.
*
* Note that all types and functions begin with the `FTC_` prefix.
*
* The cache is highly portable and thus doesn't know anything about the
* fonts installed on your system, or how to access them. This implies
* the following scheme:
*
* First, available or installed font faces are uniquely identified by
* @FTC_FaceID values, provided to the cache by the client. Note that
* the cache only stores and compares these values, and doesn't try to
* interpret them in any way.
*
* Second, the cache calls, only when needed, a client-provided function
* to convert an @FTC_FaceID into a new @FT_Face object. The latter is
* then completely managed by the cache, including its termination
* through @FT_Done_Face. To monitor termination of face objects, the
* finalizer callback in the `generic` field of the @FT_Face object can
* be used, which might also be used to store the @FTC_FaceID of the
* face.
*
* Clients are free to map face IDs to anything else. The most simple
* usage is to associate them to a (pathname,face_index) pair that is
* used to call @FT_New_Face. However, more complex schemes are also
* possible.
*
* Note that for the cache to work correctly, the face ID values must be
* **persistent**, which means that the contents they point to should not
* change at runtime, or that their value should not become invalid.
*
* If this is unavoidable (e.g., when a font is uninstalled at runtime),
* you should call @FTC_Manager_RemoveFaceID as soon as possible, to let
* the cache get rid of any references to the old @FTC_FaceID it may keep
* internally. Failure to do so will lead to incorrect behaviour or even
* crashes.
*
* To use the cache, start with calling @FTC_Manager_New to create a new
* @FTC_Manager object, which models a single cache instance. You can
* then look up @FT_Face and @FT_Size objects with
* @FTC_Manager_LookupFace and @FTC_Manager_LookupSize, respectively.
*
* If you want to use the charmap caching, call @FTC_CMapCache_New, then
* later use @FTC_CMapCache_Lookup to perform the equivalent of
* @FT_Get_Char_Index, only much faster.
*
* If you want to use the @FT_Glyph caching, call @FTC_ImageCache_New,
* then later use @FTC_ImageCache_Lookup to retrieve the corresponding
* @FT_Glyph objects from the cache.
*
* If you need lots of small bitmaps, it is much more memory efficient to
* call @FTC_SBitCache_New followed by @FTC_SBitCache_Lookup. This
* returns @FTC_SBitRec structures, which are used to store small bitmaps
* directly. (A small bitmap is one whose metrics and dimensions all fit
* into 8-bit integers).
*
* We hope to also provide a kerning cache in the near future.
*
*
* @order:
* FTC_Manager
* FTC_FaceID
* FTC_Face_Requester
*
* FTC_Manager_New
* FTC_Manager_Reset
* FTC_Manager_Done
* FTC_Manager_LookupFace
* FTC_Manager_LookupSize
* FTC_Manager_RemoveFaceID
*
* FTC_Node
* FTC_Node_Unref
*
* FTC_ImageCache
* FTC_ImageCache_New
* FTC_ImageCache_Lookup
*
* FTC_SBit
* FTC_SBitCache
* FTC_SBitCache_New
* FTC_SBitCache_Lookup
*
* FTC_CMapCache
* FTC_CMapCache_New
* FTC_CMapCache_Lookup
*
*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/***** *****/
/***** BASIC TYPE DEFINITIONS *****/
/***** *****/
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/**************************************************************************
*
* @type:
* FTC_FaceID
*
* @description:
* An opaque pointer type that is used to identity face objects. The
* contents of such objects is application-dependent.
*
* These pointers are typically used to point to a user-defined structure
* containing a font file path, and face index.
*
* @note:
* Never use `NULL` as a valid @FTC_FaceID.
*
* Face IDs are passed by the client to the cache manager that calls,
* when needed, the @FTC_Face_Requester to translate them into new
* @FT_Face objects.
*
* If the content of a given face ID changes at runtime, or if the value
* becomes invalid (e.g., when uninstalling a font), you should
* immediately call @FTC_Manager_RemoveFaceID before any other cache
* function.
*
* Failure to do so will result in incorrect behaviour or even memory
* leaks and crashes.
*/
typedef FT_Pointer FTC_FaceID;
/**************************************************************************
*
* @functype:
* FTC_Face_Requester
*
* @description:
* A callback function provided by client applications. It is used by
* the cache manager to translate a given @FTC_FaceID into a new valid
* @FT_Face object, on demand.
*
* @input:
* face_id ::
* The face ID to resolve.
*
* library ::
* A handle to a FreeType library object.
*
* req_data ::
* Application-provided request data (see note below).
*
* @output:
* aface ::
* A new @FT_Face handle.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The third parameter `req_data` is the same as the one passed by the
* client when @FTC_Manager_New is called.
*
* The face requester should not perform funny things on the returned
* face object, like creating a new @FT_Size for it, or setting a
* transformation through @FT_Set_Transform!
*/
typedef FT_Error
(*FTC_Face_Requester)( FTC_FaceID face_id,
FT_Library library,
FT_Pointer req_data,
FT_Face* aface );
/* */
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/***** *****/
/***** CACHE MANAGER OBJECT *****/
/***** *****/
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/**************************************************************************
*
* @type:
* FTC_Manager
*
* @description:
* This object corresponds to one instance of the cache-subsystem. It is
* used to cache one or more @FT_Face objects, along with corresponding
* @FT_Size objects.
*
* The manager intentionally limits the total number of opened @FT_Face
* and @FT_Size objects to control memory usage. See the `max_faces` and
* `max_sizes` parameters of @FTC_Manager_New.
*
* The manager is also used to cache 'nodes' of various types while
* limiting their total memory usage.
*
* All limitations are enforced by keeping lists of managed objects in
* most-recently-used order, and flushing old nodes to make room for new
* ones.
*/
typedef struct FTC_ManagerRec_* FTC_Manager;
/**************************************************************************
*
* @type:
* FTC_Node
*
* @description:
* An opaque handle to a cache node object. Each cache node is
* reference-counted. A node with a count of~0 might be flushed out of a
* full cache whenever a lookup request is performed.
*
* If you look up nodes, you have the ability to 'acquire' them, i.e., to
* increment their reference count. This will prevent the node from
* being flushed out of the cache until you explicitly 'release' it (see
* @FTC_Node_Unref).
*
* See also @FTC_SBitCache_Lookup and @FTC_ImageCache_Lookup.
*/
typedef struct FTC_NodeRec_* FTC_Node;
/**************************************************************************
*
* @function:
* FTC_Manager_New
*
* @description:
* Create a new cache manager.
*
* @input:
* library ::
* The parent FreeType library handle to use.
*
* max_faces ::
* Maximum number of opened @FT_Face objects managed by this cache
* instance. Use~0 for defaults.
*
* max_sizes ::
* Maximum number of opened @FT_Size objects managed by this cache
* instance. Use~0 for defaults.
*
* max_bytes ::
* Maximum number of bytes to use for cached data nodes. Use~0 for
* defaults. Note that this value does not account for managed
* @FT_Face and @FT_Size objects.
*
* requester ::
* An application-provided callback used to translate face IDs into
* real @FT_Face objects.
*
* req_data ::
* A generic pointer that is passed to the requester each time it is
* called (see @FTC_Face_Requester).
*
* @output:
* amanager ::
* A handle to a new manager object. 0~in case of failure.
*
* @return:
* FreeType error code. 0~means success.
*/
FT_EXPORT( FT_Error )
FTC_Manager_New( FT_Library library,
FT_UInt max_faces,
FT_UInt max_sizes,
FT_ULong max_bytes,
FTC_Face_Requester requester,
FT_Pointer req_data,
FTC_Manager *amanager );
/**************************************************************************
*
* @function:
* FTC_Manager_Reset
*
* @description:
* Empty a given cache manager. This simply gets rid of all the
* currently cached @FT_Face and @FT_Size objects within the manager.
*
* @inout:
* manager ::
* A handle to the manager.
*/
FT_EXPORT( void )
FTC_Manager_Reset( FTC_Manager manager );
/**************************************************************************
*
* @function:
* FTC_Manager_Done
*
* @description:
* Destroy a given manager after emptying it.
*
* @input:
* manager ::
* A handle to the target cache manager object.
*/
FT_EXPORT( void )
FTC_Manager_Done( FTC_Manager manager );
/**************************************************************************
*
* @function:
* FTC_Manager_LookupFace
*
* @description:
* Retrieve the @FT_Face object that corresponds to a given face ID
* through a cache manager.
*
* @input:
* manager ::
* A handle to the cache manager.
*
* face_id ::
* The ID of the face object.
*
* @output:
* aface ::
* A handle to the face object.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The returned @FT_Face object is always owned by the manager. You
* should never try to discard it yourself.
*
* The @FT_Face object doesn't necessarily have a current size object
* (i.e., face->size can be~0). If you need a specific 'font size', use
* @FTC_Manager_LookupSize instead.
*
* Never change the face's transformation matrix (i.e., never call the
* @FT_Set_Transform function) on a returned face! If you need to
* transform glyphs, do it yourself after glyph loading.
*
* When you perform a lookup, out-of-memory errors are detected _within_
* the lookup and force incremental flushes of the cache until enough
* memory is released for the lookup to succeed.
*
* If a lookup fails with `FT_Err_Out_Of_Memory` the cache has already
* been completely flushed, and still no memory was available for the
* operation.
*/
FT_EXPORT( FT_Error )
FTC_Manager_LookupFace( FTC_Manager manager,
FTC_FaceID face_id,
FT_Face *aface );
/**************************************************************************
*
* @struct:
* FTC_ScalerRec
*
* @description:
* A structure used to describe a given character size in either pixels
* or points to the cache manager. See @FTC_Manager_LookupSize.
*
* @fields:
* face_id ::
* The source face ID.
*
* width ::
* The character width.
*
* height ::
* The character height.
*
* pixel ::
* A Boolean. If 1, the `width` and `height` fields are interpreted as
* integer pixel character sizes. Otherwise, they are expressed as
* 1/64th of points.
*
* x_res ::
* Only used when `pixel` is value~0 to indicate the horizontal
* resolution in dpi.
*
* y_res ::
* Only used when `pixel` is value~0 to indicate the vertical
* resolution in dpi.
*
* @note:
* This type is mainly used to retrieve @FT_Size objects through the
* cache manager.
*/
typedef struct FTC_ScalerRec_
{
FTC_FaceID face_id;
FT_UInt width;
FT_UInt height;
FT_Int pixel;
FT_UInt x_res;
FT_UInt y_res;
} FTC_ScalerRec;
/**************************************************************************
*
* @struct:
* FTC_Scaler
*
* @description:
* A handle to an @FTC_ScalerRec structure.
*/
typedef struct FTC_ScalerRec_* FTC_Scaler;
/**************************************************************************
*
* @function:
* FTC_Manager_LookupSize
*
* @description:
* Retrieve the @FT_Size object that corresponds to a given
* @FTC_ScalerRec pointer through a cache manager.
*
* @input:
* manager ::
* A handle to the cache manager.
*
* scaler ::
* A scaler handle.
*
* @output:
* asize ::
* A handle to the size object.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The returned @FT_Size object is always owned by the manager. You
* should never try to discard it by yourself.
*
* You can access the parent @FT_Face object simply as `size->face` if
* you need it. Note that this object is also owned by the manager.
*
* @note:
* When you perform a lookup, out-of-memory errors are detected _within_
* the lookup and force incremental flushes of the cache until enough
* memory is released for the lookup to succeed.
*
* If a lookup fails with `FT_Err_Out_Of_Memory` the cache has already
* been completely flushed, and still no memory is available for the
* operation.
*/
FT_EXPORT( FT_Error )
FTC_Manager_LookupSize( FTC_Manager manager,
FTC_Scaler scaler,
FT_Size *asize );
/**************************************************************************
*
* @function:
* FTC_Node_Unref
*
* @description:
* Decrement a cache node's internal reference count. When the count
* reaches 0, it is not destroyed but becomes eligible for subsequent
* cache flushes.
*
* @input:
* node ::
* The cache node handle.
*
* manager ::
* The cache manager handle.
*/
FT_EXPORT( void )
FTC_Node_Unref( FTC_Node node,
FTC_Manager manager );
/**************************************************************************
*
* @function:
* FTC_Manager_RemoveFaceID
*
* @description:
* A special function used to indicate to the cache manager that a given
* @FTC_FaceID is no longer valid, either because its content changed, or
* because it was deallocated or uninstalled.
*
* @input:
* manager ::
* The cache manager handle.
*
* face_id ::
* The @FTC_FaceID to be removed.
*
* @note:
* This function flushes all nodes from the cache corresponding to this
* `face_id`, with the exception of nodes with a non-null reference
* count.
*
* Such nodes are however modified internally so as to never appear in
* later lookups with the same `face_id` value, and to be immediately
* destroyed when released by all their users.
*
*/
FT_EXPORT( void )
FTC_Manager_RemoveFaceID( FTC_Manager manager,
FTC_FaceID face_id );
/**************************************************************************
*
* @type:
* FTC_CMapCache
*
* @description:
* An opaque handle used to model a charmap cache. This cache is to hold
* character codes -> glyph indices mappings.
*
*/
typedef struct FTC_CMapCacheRec_* FTC_CMapCache;
/**************************************************************************
*
* @function:
* FTC_CMapCache_New
*
* @description:
* Create a new charmap cache.
*
* @input:
* manager ::
* A handle to the cache manager.
*
* @output:
* acache ::
* A new cache handle. `NULL` in case of error.
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* Like all other caches, this one will be destroyed with the cache
* manager.
*
*/
FT_EXPORT( FT_Error )
FTC_CMapCache_New( FTC_Manager manager,
FTC_CMapCache *acache );
/**************************************************************************
*
* @function:
* FTC_CMapCache_Lookup
*
* @description:
* Translate a character code into a glyph index, using the charmap
* cache.
*
* @input:
* cache ::
* A charmap cache handle.
*
* face_id ::
* The source face ID.
*
* cmap_index ::
* The index of the charmap in the source face. Any negative value
* means to use the cache @FT_Face's default charmap.
*
* char_code ::
* The character code (in the corresponding charmap).
*
* @return:
* Glyph index. 0~means 'no glyph'.
*
*/
FT_EXPORT( FT_UInt )
FTC_CMapCache_Lookup( FTC_CMapCache cache,
FTC_FaceID face_id,
FT_Int cmap_index,
FT_UInt32 char_code );
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/***** *****/
/***** IMAGE CACHE OBJECT *****/
/***** *****/
/*************************************************************************/
/*************************************************************************/
/*************************************************************************/
/**************************************************************************
*
* @struct:
* FTC_ImageTypeRec
*
* @description:
* A structure used to model the type of images in a glyph cache.
*
* @fields:
* face_id ::
* The face ID.
*
* width ::
* The width in pixels.
*
* height ::
* The height in pixels.
*
* flags ::
* The load flags, as in @FT_Load_Glyph.
*
*/
typedef struct FTC_ImageTypeRec_
{
FTC_FaceID face_id;
FT_UInt width;
FT_UInt height;
FT_Int32 flags;
} FTC_ImageTypeRec;
/**************************************************************************
*
* @type:
* FTC_ImageType
*
* @description:
* A handle to an @FTC_ImageTypeRec structure.
*
*/
typedef struct FTC_ImageTypeRec_* FTC_ImageType;
/* */
#define FTC_IMAGE_TYPE_COMPARE( d1, d2 ) \
( (d1)->face_id == (d2)->face_id && \
(d1)->width == (d2)->width && \
(d1)->flags == (d2)->flags )
/**************************************************************************
*
* @type:
* FTC_ImageCache
*
* @description:
* A handle to a glyph image cache object. They are designed to hold
* many distinct glyph images while not exceeding a certain memory
* threshold.
*/
typedef struct FTC_ImageCacheRec_* FTC_ImageCache;
/**************************************************************************
*
* @function:
* FTC_ImageCache_New
*
* @description:
* Create a new glyph image cache.
*
* @input:
* manager ::
* The parent manager for the image cache.
*
* @output:
* acache ::
* A handle to the new glyph image cache object.
*
* @return:
* FreeType error code. 0~means success.
*/
FT_EXPORT( FT_Error )
FTC_ImageCache_New( FTC_Manager manager,
FTC_ImageCache *acache );
/**************************************************************************
*
* @function:
* FTC_ImageCache_Lookup
*
* @description:
* Retrieve a given glyph image from a glyph image cache.
*
* @input:
* cache ::
* A handle to the source glyph image cache.
*
* type ::
* A pointer to a glyph image type descriptor.
*
* gindex ::
* The glyph index to retrieve.
*
* @output:
* aglyph ::
* The corresponding @FT_Glyph object. 0~in case of failure.
*
* anode ::
* Used to return the address of the corresponding cache node after
* incrementing its reference count (see note below).
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The returned glyph is owned and managed by the glyph image cache.
* Never try to transform or discard it manually! You can however create
* a copy with @FT_Glyph_Copy and modify the new one.
*
* If `anode` is _not_ `NULL`, it receives the address of the cache node
* containing the glyph image, after increasing its reference count.
* This ensures that the node (as well as the @FT_Glyph) will always be
* kept in the cache until you call @FTC_Node_Unref to 'release' it.
*
* If `anode` is `NULL`, the cache node is left unchanged, which means
* that the @FT_Glyph could be flushed out of the cache on the next call
* to one of the caching sub-system APIs. Don't assume that it is
* persistent!
*/
FT_EXPORT( FT_Error )
FTC_ImageCache_Lookup( FTC_ImageCache cache,
FTC_ImageType type,
FT_UInt gindex,
FT_Glyph *aglyph,
FTC_Node *anode );
/**************************************************************************
*
* @function:
* FTC_ImageCache_LookupScaler
*
* @description:
* A variant of @FTC_ImageCache_Lookup that uses an @FTC_ScalerRec to
* specify the face ID and its size.
*
* @input:
* cache ::
* A handle to the source glyph image cache.
*
* scaler ::
* A pointer to a scaler descriptor.
*
* load_flags ::
* The corresponding load flags.
*
* gindex ::
* The glyph index to retrieve.
*
* @output:
* aglyph ::
* The corresponding @FT_Glyph object. 0~in case of failure.
*
* anode ::
* Used to return the address of the corresponding cache node after
* incrementing its reference count (see note below).
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The returned glyph is owned and managed by the glyph image cache.
* Never try to transform or discard it manually! You can however create
* a copy with @FT_Glyph_Copy and modify the new one.
*
* If `anode` is _not_ `NULL`, it receives the address of the cache node
* containing the glyph image, after increasing its reference count.
* This ensures that the node (as well as the @FT_Glyph) will always be
* kept in the cache until you call @FTC_Node_Unref to 'release' it.
*
* If `anode` is `NULL`, the cache node is left unchanged, which means
* that the @FT_Glyph could be flushed out of the cache on the next call
* to one of the caching sub-system APIs. Don't assume that it is
* persistent!
*
* Calls to @FT_Set_Char_Size and friends have no effect on cached
* glyphs; you should always use the FreeType cache API instead.
*/
FT_EXPORT( FT_Error )
FTC_ImageCache_LookupScaler( FTC_ImageCache cache,
FTC_Scaler scaler,
FT_ULong load_flags,
FT_UInt gindex,
FT_Glyph *aglyph,
FTC_Node *anode );
/**************************************************************************
*
* @type:
* FTC_SBit
*
* @description:
* A handle to a small bitmap descriptor. See the @FTC_SBitRec structure
* for details.
*/
typedef struct FTC_SBitRec_* FTC_SBit;
/**************************************************************************
*
* @struct:
* FTC_SBitRec
*
* @description:
* A very compact structure used to describe a small glyph bitmap.
*
* @fields:
* width ::
* The bitmap width in pixels.
*
* height ::
* The bitmap height in pixels.
*
* left ::
* The horizontal distance from the pen position to the left bitmap
* border (a.k.a. 'left side bearing', or 'lsb').
*
* top ::
* The vertical distance from the pen position (on the baseline) to the
* upper bitmap border (a.k.a. 'top side bearing'). The distance is
* positive for upwards y~coordinates.
*
* format ::
* The format of the glyph bitmap (monochrome or gray).
*
* max_grays ::
* Maximum gray level value (in the range 1 to~255).
*
* pitch ::
* The number of bytes per bitmap line. May be positive or negative.
*
* xadvance ::
* The horizontal advance width in pixels.
*
* yadvance ::
* The vertical advance height in pixels.
*
* buffer ::
* A pointer to the bitmap pixels.
*/
typedef struct FTC_SBitRec_
{
FT_Byte width;
FT_Byte height;
FT_Char left;
FT_Char top;
FT_Byte format;
FT_Byte max_grays;
FT_Short pitch;
FT_Char xadvance;
FT_Char yadvance;
FT_Byte* buffer;
} FTC_SBitRec;
/**************************************************************************
*
* @type:
* FTC_SBitCache
*
* @description:
* A handle to a small bitmap cache. These are special cache objects
* used to store small glyph bitmaps (and anti-aliased pixmaps) in a much
* more efficient way than the traditional glyph image cache implemented
* by @FTC_ImageCache.
*/
typedef struct FTC_SBitCacheRec_* FTC_SBitCache;
/**************************************************************************
*
* @function:
* FTC_SBitCache_New
*
* @description:
* Create a new cache to store small glyph bitmaps.
*
* @input:
* manager ::
* A handle to the source cache manager.
*
* @output:
* acache ::
* A handle to the new sbit cache. `NULL` in case of error.
*
* @return:
* FreeType error code. 0~means success.
*/
FT_EXPORT( FT_Error )
FTC_SBitCache_New( FTC_Manager manager,
FTC_SBitCache *acache );
/**************************************************************************
*
* @function:
* FTC_SBitCache_Lookup
*
* @description:
* Look up a given small glyph bitmap in a given sbit cache and 'lock' it
* to prevent its flushing from the cache until needed.
*
* @input:
* cache ::
* A handle to the source sbit cache.
*
* type ::
* A pointer to the glyph image type descriptor.
*
* gindex ::
* The glyph index.
*
* @output:
* sbit ::
* A handle to a small bitmap descriptor.
*
* anode ::
* Used to return the address of the corresponding cache node after
* incrementing its reference count (see note below).
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The small bitmap descriptor and its bit buffer are owned by the cache
* and should never be freed by the application. They might as well
* disappear from memory on the next cache lookup, so don't treat them as
* persistent data.
*
* The descriptor's `buffer` field is set to~0 to indicate a missing
* glyph bitmap.
*
* If `anode` is _not_ `NULL`, it receives the address of the cache node
* containing the bitmap, after increasing its reference count. This
* ensures that the node (as well as the image) will always be kept in
* the cache until you call @FTC_Node_Unref to 'release' it.
*
* If `anode` is `NULL`, the cache node is left unchanged, which means
* that the bitmap could be flushed out of the cache on the next call to
* one of the caching sub-system APIs. Don't assume that it is
* persistent!
*/
FT_EXPORT( FT_Error )
FTC_SBitCache_Lookup( FTC_SBitCache cache,
FTC_ImageType type,
FT_UInt gindex,
FTC_SBit *sbit,
FTC_Node *anode );
/**************************************************************************
*
* @function:
* FTC_SBitCache_LookupScaler
*
* @description:
* A variant of @FTC_SBitCache_Lookup that uses an @FTC_ScalerRec to
* specify the face ID and its size.
*
* @input:
* cache ::
* A handle to the source sbit cache.
*
* scaler ::
* A pointer to the scaler descriptor.
*
* load_flags ::
* The corresponding load flags.
*
* gindex ::
* The glyph index.
*
* @output:
* sbit ::
* A handle to a small bitmap descriptor.
*
* anode ::
* Used to return the address of the corresponding cache node after
* incrementing its reference count (see note below).
*
* @return:
* FreeType error code. 0~means success.
*
* @note:
* The small bitmap descriptor and its bit buffer are owned by the cache
* and should never be freed by the application. They might as well
* disappear from memory on the next cache lookup, so don't treat them as
* persistent data.
*
* The descriptor's `buffer` field is set to~0 to indicate a missing
* glyph bitmap.
*
* If `anode` is _not_ `NULL`, it receives the address of the cache node
* containing the bitmap, after increasing its reference count. This
* ensures that the node (as well as the image) will always be kept in
* the cache until you call @FTC_Node_Unref to 'release' it.
*
* If `anode` is `NULL`, the cache node is left unchanged, which means
* that the bitmap could be flushed out of the cache on the next call to
* one of the caching sub-system APIs. Don't assume that it is
* persistent!
*/
FT_EXPORT( FT_Error )
FTC_SBitCache_LookupScaler( FTC_SBitCache cache,
FTC_Scaler scaler,
FT_ULong load_flags,
FT_UInt gindex,
FTC_SBit *sbit,
FTC_Node *anode );
/* */
FT_END_HEADER
#endif /* FTCACHE_H_ */
/* END */