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Improve ot-svg callback hooks documentation

This commit is contained in:
Moazin Khatti 2019-08-24 18:24:28 +05:00
parent 67c108bc9c
commit eb9a614011
1 changed files with 33 additions and 11 deletions
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44
include/freetype/otsvg.h
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@ -36,12 +36,15 @@ FT_BEGIN_HEADER
* SVG_Lib_Init_Func
*
* @description:
* A callback used to initiate the SVG Rendering port.
* A callback which is called when the first OT-SVG glyph is rendered in
* the lifetime of an @FT_Library object. The callback should perform all
* sorts of initializations that the SVG rendering library needs such as
* allocating memory for `svg_renderer_state` of @FT_LibraryRec.
*
* @input:
* library ::
* A instance of library. This is required to initialize the
* renderer's state which will be held in the library.
* An instance of @FT_Library. It's passed to give the callbacks access
* to `svg_renderer_state` of @FT_LibraryRec.
*
* @return:
* FreeType error code. 0 means success.
@ -56,13 +59,15 @@ FT_BEGIN_HEADER
* SVG_Lib_Free_Func
*
* @description:
* A callback used to free the SVG Rendering port. Calling this callback
* shall do all cleanups that the SVG Rendering port wants to do.
* A callback which is called when the `ot-svg` module is being freed.
* It is only called only if the init hook was called earlier. So, if no
* OT-SVG glyph is rendered, neither the init hook is called nor the free
* hook.
*
* @input:
* library ::
* A instance of library. This is required to free the renderer's
* state which will be held in the library.
* An instance of @FT_Library. It's passed to give the callbacks access
* to `svg_renderer_state` of @FT_LibraryRec.
*/
typedef void
(*SVG_Lib_Free_Func)( FT_Library library );
@ -74,11 +79,15 @@ FT_BEGIN_HEADER
* SVG_Lib_Render_Func
*
* @description:
* A callback used to render the glyph loaded in the slot.
* A callback which is called to render an OT-SVG glyph. This callback
* hook is called right after the preset hook 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 `other` field of
* @FT_GlyphSlotRec.
*
* @input:
* slot ::
* The whole glyph slot object.
* The slot to render.
*
* @return:
* FreeType error code. 0 means success.
@ -92,12 +101,26 @@ FT_BEGIN_HEADER
* SVG_Lib_Preset_Slot_Func
*
* @description:
* A callback which is to preset the glyphslot.
* A callback which is called to preset the glyphslot. It is called from
* two places.
*
* 1. When `FT_Load_Glyph` needs to preset the glyphslot.
* 2. Right before the `ot-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 while presetting a glyphslot many calculations
* are needed and later the render callback hook needs the same
* calculations, thus, if `cache` is `TRUE`, the hook might _cache_ these
* calculations in `svg_renderer_state` of @FT_LibraryRec.
*
* @input:
* slot ::
* The glyph slot which has the SVG document loaded.
*
* cache ::
* See description.
*
* @return:
* FreeType error code. 0 means success.
*/
@ -130,7 +153,6 @@ FT_BEGIN_HEADER
*/
typedef struct SVG_RendererHooks_
{
/* Api Hooks for OT-SVG Rendering */
SVG_Lib_Init_Func init_svg;
SVG_Lib_Free_Func free_svg;
SVG_Lib_Render_Func render_svg;