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/****************************************************************************
*
* otsvg.h
*
* Interface for OT-SVG support related things (specification).
*
* Copyright (C) 2004-2019 by
* David Turner, Robert Wilhelm, Werner Lemberg and Moazin Khatti.
*
* 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 FTSVG_RENDERER_H_
#define FTSVG_RENDERER_H_
#include <ft2build.h>
#include FT_FREETYPE_H
#ifdef FREETYPE_H
#error "freetype.h of FreeType 1 has been loaded!"
#error "Please fix the directory search order for header files"
#error "so that freetype.h of FreeType 2 is found first."
#endif
FT_BEGIN_HEADER
/**************************************************************************
*
* @functype:
* SVG_Lib_Init_Func
*
* @description:
* 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 ::
* 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.
*/
typedef FT_Error
(*SVG_Lib_Init_Func)( FT_Library library );
/**************************************************************************
*
* @functype:
* SVG_Lib_Free_Func
*
* @description:
* 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 ::
* 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 );
/**************************************************************************
*
* @functype:
* SVG_Lib_Render_Func
*
* @description:
* 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 slot to render.
*
* @return:
* FreeType error code. 0 means success.
*/
typedef FT_Error
(*SVG_Lib_Render_Func)( FT_GlyphSlot slot );
/**************************************************************************
*
* @functype:
* SVG_Lib_Preset_Slot_Func
*
* @description:
* 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.
*/
typedef FT_Error
(*SVG_Lib_Preset_Slot_Func)( FT_GlyphSlot slot, FT_Bool cache);
/**************************************************************************
*
* @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.
*
* @fields:
* init_svg ::
* The initialization hook.
*
* free_svg ::
* The cleanup hook.
*
* render_hook ::
* The render hook.
*
* preset_slot ::
* The preset hook.
*/
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:
* FT_SVG_DocumentRec_
*
* @description:
* A structure that models one SVG document.
*
* @fields:
* svg_document ::
* A pointer to the SVG document.
*
* svg_document_length ::
* The length of `svg_document`.
*
* metrics ::
* A metrics object storing the size information.
*
* units_per_EM ::
* The size of the EM square.
*
* start_glyph_id ::
* The first glyph ID in the glyph range is covered by this document.
*
* end_glyph_id ::
* The last glyph ID in the glyph range is covered by this document.
*
* transform ::
* A 2x2 transformation matrix to apply on the glyph while rendering it.
*
* delta ::
* Translation to apply on the glyph while rendering.
*
* @note:
* `metrics` and `units_per_EM` might look like repetitions since both
* fields are stored in face object, but they are not; When the slot is
* passed down to a renderer, the renderer can only access the `metrics`
* and `units_per_EM` by `slot->face`. However, when `FT_Glyph_To_Bitmap`
* sets up a dummy object, it has no way to set a `face` object. Thus,
* metrics information and units_per_EM (which is necessary for OT-SVG)
* has to be stored separately.
*/
typedef struct FT_SVG_DocumentRec_
{
FT_Byte* svg_document;
FT_ULong svg_document_length;
FT_Size_Metrics metrics;
FT_UShort units_per_EM;
FT_UShort start_glyph_id;
FT_UShort end_glyph_id;
FT_Matrix transform;
FT_Vector delta;
} FT_SVG_DocumentRec;
/**************************************************************************
*
* @type:
* FT_SVG_Document
*
* @description:
* A handle to a FT_SVG_DocumentRec object.
*/
typedef struct FT_SVG_DocumentRec_* FT_SVG_Document;
FT_END_HEADER
#endif
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