ref: f6be92767d1d002f5e90a4673ee4e6d4f1e1744f
parent: 9cc89717be988ec5922fe029e5a4cf283efb0b0c
author: Chris Liddell <chris.liddell@artifex.com>
date: Wed Dec 16 01:03:10 EST 2020
[truetype] Fix incremental metrics (#59503). * src/truetype/ttgload.c (tt_get_metrics, load_truetype_glyph): Previously, the code would populate the phantom points before calling the `get_glyph_metrics` callback. For formats like PCL XL format 1, class 2 downloaded fonts (where metrics are removed from the TTF header), this causes problems when the hinting program uses the phantom points (misplaced and distorted glyphs) due to the metrics being unset (all zeros). (tt_get_metrics_incr_overrides): Renamed to... (tt_get_metrics_incremental): ... this. Updated caller * include/freetype/ftincrem.h: Update the documentation to make it clearer that `get_glyph_metrics` is to retrieve metrics from a non-standard source, but *not* for the purpose of imposing custom metrics.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,22 @@
+2020-12-16 Chris Liddell <chris.liddell@artifex.com>
+
+ [truetype] Fix incremental metrics (#59503).
+
+ * src/truetype/ttgload.c (tt_get_metrics, load_truetype_glyph):
+ Previously, the code would populate the phantom points before
+ calling the `get_glyph_metrics` callback. For formats like PCL XL
+ format 1, class 2 downloaded fonts (where metrics are removed from
+ the TTF header), this causes problems when the hinting program uses
+ the phantom points (misplaced and distorted glyphs) due to the
+ metrics being unset (all zeros).
+ (tt_get_metrics_incr_overrides): Renamed to...
+ (tt_get_metrics_incremental): ... this. Updated caller
+
+ * include/freetype/ftincrem.h: Update the documentation to make it
+ clearer that `get_glyph_metrics` is to retrieve metrics from a
+ non-standard source, but *not* for the purpose of imposing custom
+ metrics.
+
2020-12-14 Werner Lemberg <wl@gnu.org>
[type42] Pacify static analysis tools (#59682).
--- a/include/freetype/ftincrem.h
+++ b/include/freetype/ftincrem.h
@@ -213,9 +213,14 @@
*
* @description:
* A function used to retrieve the basic metrics of a given glyph index
- * before accessing its data. This is necessary because, in certain
- * formats like TrueType, the metrics are stored in a different place
- * from the glyph images proper.
+ * before accessing its data. This allows for handling font types such
+ * as PCL~XL Format~1, Class~2 downloaded TrueType fonts, where the glyph
+ * metrics (`hmtx` and `vmtx` tables) are permitted to be omitted from
+ * the font, and the relevant metrics included in the header of the glyph
+ * outline data. Importantly, this is not intended to allow custom glyph
+ * metrics (for example, Postscript Metrics dictionaries), because that
+ * conflicts with the requirements of outline hinting. Such custom
+ * metrics must be handled separately, by the calling application.
*
* @input:
* incremental ::
@@ -235,7 +240,7 @@
*
* @output:
* ametrics ::
- * The replacement glyph metrics in font units.
+ * The glyph metrics in font units.
*
*/
typedef FT_Error
@@ -264,7 +269,7 @@
*
* get_glyph_metrics ::
* The function to get glyph metrics. May be null if the font does not
- * provide overriding glyph metrics.
+ * require it.
*
*/
typedef struct FT_Incremental_FuncsRec_
--- a/src/truetype/ttgload.c
+++ b/src/truetype/ttgload.c
@@ -197,10 +197,17 @@
}
#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
- if ( !loader->linear_def )
+#ifdef FT_CONFIG_OPTION_INCREMENTAL
+ /* With the incremental interface, these values are set by */
+ /* a call to `tt_get_metrics_incremental'. */
+ if ( face->root.internal->incremental_interface == NULL )
+#endif
{- loader->linear_def = 1;
- loader->linear = advance_width;
+ if ( !loader->linear_def )
+ {+ loader->linear_def = 1;
+ loader->linear = advance_width;
+ }
}
return FT_Err_Ok;
@@ -210,8 +217,8 @@
#ifdef FT_CONFIG_OPTION_INCREMENTAL
static void
- tt_get_metrics_incr_overrides( TT_Loader loader,
- FT_UInt glyph_index )
+ tt_get_metrics_incremental( TT_Loader loader,
+ FT_UInt glyph_index )
{TT_Face face = loader->face;
@@ -1741,14 +1748,12 @@
if ( loader->byte_len == 0 || loader->n_contours == 0 )
{- /* must initialize points before (possibly) overriding */
- /* glyph metrics from the incremental interface */
- tt_loader_set_pp( loader );
-
#ifdef FT_CONFIG_OPTION_INCREMENTAL
- tt_get_metrics_incr_overrides( loader, glyph_index );
+ tt_get_metrics_incremental( loader, glyph_index );
#endif
+ tt_loader_set_pp( loader );
+
#ifdef TT_CONFIG_OPTION_GX_VAR_SUPPORT
if ( FT_IS_NAMED_INSTANCE( FT_FACE( face ) ) ||
@@ -1830,13 +1835,11 @@
goto Exit;
}
- /* must initialize phantom points before (possibly) overriding */
- /* glyph metrics from the incremental interface */
- tt_loader_set_pp( loader );
-
#ifdef FT_CONFIG_OPTION_INCREMENTAL
- tt_get_metrics_incr_overrides( loader, glyph_index );
+ tt_get_metrics_incremental( loader, glyph_index );
#endif
+ tt_loader_set_pp( loader );
+
/***********************************************************************/
/***********************************************************************/