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Diffstat (limited to 'include/freetype/otsvg.h')
| -rw-r--r-- | include/freetype/otsvg.h | 211 |
1 files changed, 211 insertions, 0 deletions
diff --git a/include/freetype/otsvg.h b/include/freetype/otsvg.h index b8ff84f7b..87482491c 100644 --- a/include/freetype/otsvg.h +++ b/include/freetype/otsvg.h @@ -30,6 +30,217 @@ FT_BEGIN_HEADER + + /************************************************************************** + * + * @functype: + * SVG_Lib_Init_Func + * + * @description: + * A callback that is called when the first OT-SVG glyph is rendered in + * the lifetime of an @FT_Library object. In a typical implementation, + * one would want to allocate a structure and point the `data_pointer` + * to it and perform any library initializations that might be needed. + * + * For more information on the implementation, see our standard hooks + * based on Librsvg in the 'FreeType Demo Programs' repository. + * + * @inout: + * data_pointer :: + * The SVG rendering module stores a pointer variable that can be used + * by clients to store any data that needs to be shared across + * different hooks. `data_pointer` is essentially a pointer to that + * pointer such that it can be written to as well as read from. + * + * @return: + * FreeType error code. 0 means success. + * + * @since: + * 2.12 + */ + typedef FT_Error + (*SVG_Lib_Init_Func)( FT_Pointer *data_pointer ); + + + /************************************************************************** + * + * @functype: + * SVG_Lib_Free_Func + * + * @description: + * A callback that is called when the `ot-svg` module is being freed. + * It is only called if the init hook was called earlier. This means + * that neither the init nor the free hook is called if no OT-SVG glyph + * is rendered. + * + * In a typical implementation, one would want to free any state + * structure that was allocated in the init hook and perform any + * library-related closure that might be needed. + * + * For more information on the implementation, see our standard hooks + * based on Librsvg in the 'FreeType Demo Programs' repository. + * + * @inout: + * data_pointer :: + * The SVG rendering module stores a pointer variable that can be used + * by clients to store any data that needs to be shared across + * different hooks. `data_pointer` is essentially a pointer to that + * pointer such that it can be written to as well as read from. + * + * @since: + * 2.12 + */ + typedef void + (*SVG_Lib_Free_Func)( FT_Pointer *data_pointer ); + + + /************************************************************************** + * + * @functype: + * SVG_Lib_Render_Func + * + * @description: + * A callback that is called to render an OT-SVG glyph. This callback + * hook is called right after the preset hook @SVG_Lib_Preset_SlotFunc + * has been called with `cache` set to `TRUE`. The data necessary to + * render is available through the handle @FT_SVG_Document, which is set + * in the `other` field of @FT_GlyphSlotRec. + * + * The render hook is expected to render the SVG glyph to the bitmap + * buffer that is allocated already at `slot->bitmap.buffer`. It also + * sets the `num_grays` value as well as `slot->format`. + * + * For more information on the implementation, see our standard hooks + * based on Librsvg in the 'FreeType Demo Programs' repository. + * + * @input: + * slot :: + * The slot to render. + * + * @inout: + * data_pointer :: + * The SVG rendering module stores a pointer variable that can be used + * by clients to store any data that needs to be shared across + * different hooks. `data_pointer` is essentially a pointer to that + * pointer such that it can be written to as well as read from. + * + * @return: + * FreeType error code. 0 means success. + * + * @since: + * 2.12 + */ + typedef FT_Error + (*SVG_Lib_Render_Func)( FT_GlyphSlot slot, + FT_Pointer *data_pointer ); + + + /************************************************************************** + * + * @functype: + * SVG_Lib_Preset_Slot_Func + * + * @description: + * A callback that is called to preset the glyph slot. It is called from + * two places. + * + * 1. When `FT_Load_Glyph` needs to preset the glyph slot. + * 2. Right before the `svg` module calls the render callback hook. + * + * When it is the former, the argument `cache` is set to `FALSE`. When + * it is the latter, the argument `cache` is set to `TRUE`. This + * distinction has been made because many calculations that are necessary + * for presetting a glyph slot are the same needed later for the render + * callback hook. Thus, if `cache` is `TRUE`, the hook can _cache_ those + * calculations in a memory block referenced by the state pointer. + * + * This hook is expected to preset the slot by setting parameters such as + * `bitmap_left`, `bitmap_top`, `width`, `rows`, `pitch`, and + * `pixel_mode`. It is also expected to set all the metrics for the slot + * including the vertical advance if it is not already set. Typically, + * fonts have horizontal advances but not vertical ones. If those are + * available, they had already been set, otherwise they have to be + * estimated and set manually. The hook must take into account the + * transformations that have been set, and translate the transformation + * matrices into the SVG coordinate system, as the original matrix is + * intended for the TTF/CFF coordinate system. + * + * For more information on the implementation, see our standard hooks + * based on Librsvg in the 'FreeType Demo Programs' repository. + * + * @input: + * slot :: + * The glyph slot that has the SVG document loaded. + * + * cache :: + * See description. + * + * @inout: + * data_pointer :: + * The SVG rendering module stores a pointer variable that can be used + * by clients to store any data that needs to be shared across + * different hooks. `data_pointer` is essentially a pointer to that + * pointer such that it can be written to as well as read from. + * + * @return: + * FreeType error code. 0 means success. + * + * @since: + * 2.12 + */ + typedef FT_Error + (*SVG_Lib_Preset_Slot_Func)( FT_GlyphSlot slot, + FT_Bool cache, + FT_Pointer *state ); + + + /************************************************************************** + * + * @struct: + * SVG_RendererHooks + * + * @description: + * A structure that stores the four hooks needed to render OT-SVG glyphs + * properly. The structure is publicly used to set the hooks via driver + * properties. + * + * The behavior of each hook is described in its documentation. One + * thing to note is that the preset hook and the render hook often need + * to do the same operations; therefore, it's better to cache the + * intermediate data in a state structure to avoid calculating it twice. + * For example, in the preset hook one can draw the glyph on a recorder + * surface and later create a bitmap surface from it in the render hook. + * + * For more information on the implementation, see our standard hooks + * based on Librsvg in the 'FreeType Demo Programs' repository. + * + * @fields: + * init_svg :: + * The initialization hook. + * + * free_svg :: + * The cleanup hook. + * + * render_hook :: + * The render hook. + * + * preset_slot :: + * The preset hook. + * + * @since: + * 2.12 + */ + typedef struct SVG_RendererHooks_ + { + SVG_Lib_Init_Func init_svg; + SVG_Lib_Free_Func free_svg; + SVG_Lib_Render_Func render_svg; + + SVG_Lib_Preset_Slot_Func preset_slot; + + } SVG_RendererHooks; + + /************************************************************************** * * @struct: |