[Git][freetype/freetype][master] Proposal: Feature control for variable COLRv1

[@drott]

Dominik Röttsches pushed to branch master at FreeType / FreeType

Commits:

• 4b6f92e6
  by Dominik Röttsches at 2022-06-21T12:25:46+03:00

  Proposal: Feature control for variable COLRv1
  
  * include/freetype/ftdriver.h (variable-color-v1 property): Add documentation
  for variable-colr-v1 property.
  * src/truetype/ttdriver.c (tt_property_set): Ingest variable-control property
  when called, set to enable_variable_colrv1 driver flag.
  * src/truetype/ttobjs.h (TT_DriverRec): Add enable_variable_colrv1 flag.
  

3 changed files:

• include/freetype/ftdriver.h
• src/truetype/ttdriver.c
• src/truetype/ttobjs.h

Changes:

include/freetype/ftdriver.h

---

...	...	@@ -214,9 +214,9 @@ FT_BEGIN_HEADER
214	214	* itself, it is possible to control its behaviour with @FT_Property_Set
215	215	* and @FT_Property_Get.
216	216	*
217		- * The TrueType driver's module name is 'truetype'; a single property
218		- * @interpreter-version is available, as documented in the @properties
219		- * section.
	217	+ * The TrueType driver's module name is 'truetype'; two properties are
	218	+ * available, @interpreter-version and @TEMPORARY-enable-variable-colrv1, as
	219	+ * documented in the @properties section.
220	220	*
221	221	* To help understand the differences between interpreter versions, we
222	222	* introduce a list of definitions, kindly provided by Greg Hitchcock.
...	...	@@ -820,6 +820,48 @@ FT_BEGIN_HEADER
820	820	* 2.5
821	821	*/
822	822
	823	+ /**************************************************************************
	824	+ *
	825	+ * @property:
	826	+ * TEMPORARY-enable-variable-colrv1
	827	+ *
	828	+ * @description:
	829	+ * Controls experimental support of variable COLRv1 and whether the COLRv1
	830	+ * implementation should take into account variation deltas. This tells the
	831	+ * COLRv1 API methods whether they should read from the font and apply
	832	+ * variable deltas to COLRv1 properties. The feature is default off. When
	833	+ * on, variable COLRv1 deltas are applied for COLRv1 features for which they
	834	+ * are already implemented. When off, variable deltas are ignored even if
	835	+ * the respective PaintVar* table may already be understood.
	836	+ *
	837	+ * WARNING: Temporary flag during development of variable COLRv1. This flag
	838	+ * will be removed, do not rely on it. Full variable COLRv1 support will be
	839	+ * announced separately.
	840	+ *
	841	+ * @note:
	842	+ * This property cannot be set via the `FREETYPE_PROPERTIES` environment
	843	+ * variable.
	844	+ *
	845	+ * @example:
	846	+ * The following example code demonstrates how to enable variable
	847	+ * COLRv1.
	848	+ *
	849	+ * ```
	850	+ * FT_Library library;
	851	+ * FT_Face face;
	852	+ * FT_Bool variable_colrv1 = TRUE;
	853	+ *
	854	+ *
	855	+ * FT_Init_FreeType( &library );
	856	+ *
	857	+ * FT_Property_Set( library, "truetype",
	858	+ * "TEMPORARY-enable-variable-colrv1",
	859	+ * &variable_colr_v1 );
	860	+ * ```
	861	+ *
	862	+ * @since:
	863	+ * 2.12.2
	864	+ */
823	865
824	866	/**************************************************************************
825	867	*

src/truetype/ttdriver.c

---

...	...	@@ -108,6 +108,23 @@
108	108	return error;
109	109	}
110	110
	111	+ if ( !ft_strcmp( property_name, "TEMPORARY-enable-variable-colrv1" ) )
	112	+ {
	113	+ /* This flag is temporary and can't be set with environment variables. */
	114	+ if ( !value_is_string )
	115	+ {
	116	+ FT_Bool* bv = (FT_Bool*)value;
	117	+
	118	+ if ( *bv == TRUE || *bv == FALSE)
	119	+ driver->enable_variable_colrv1 = *bv;
	120	+ else
	121	+ error = FT_ERR( Unimplemented_Feature );
	122	+ } else
	123	+ error = FT_ERR( Invalid_Argument );
	124	+
	125	+ return error;
	126	+ }
	127	+
111	128	FT_TRACE2(( "tt_property_set: missing property `%s'\n",
112	129	property_name ));
113	130	return FT_THROW( Missing_Property );

src/truetype/ttobjs.h

---

...	...	@@ -337,6 +337,8 @@ FT_BEGIN_HEADER
337	337
338	338	FT_UInt interpreter_version;
339	339
	340	+ FT_Bool enable_variable_colrv1;
	341	+
340	342	} TT_DriverRec;
341	343
342	344

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