ref: b45043c44030337c1f7006f8c3d19fdfffe541f6
parent: e77ee789faaf5697143027452df6669afede0a57
author: Werner Lemberg <[email protected]>
date: Fri Aug 11 05:34:20 EDT 2017
[sfnt, truetype] Improve handling of missing sbits. Requested by Behdad. Modern bitmap-only SFNTs like `NotoColorEmoji.ttf' don't contain entries in the bitmap strike(s) for empty glyphs. Instead, they rely that a space glyph gets created from the font's metrics data. This commit makes FreeType behave accordingly. * include/freetype/fterrdef.h (FT_Err_Missing_Bitmap): New error code. * src/sfnt/ttsbit.c (tt_sbit_decoder_load_image): Change error codes to make a distinction between a missing bitmap in a composite and a simple missing bitmap. * src/truetype/ttgload.c (TT_Load_Glyph): For a missing bitmap (in a bitmap-only font), synthesize an empty bitmap glyph if metrics are available.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,25 @@
+2017-08-11 Werner Lemberg <[email protected]>
+
+ [sfnt, truetype] Improve handling of missing sbits.
+
+ Requested by Behdad.
+
+ Modern bitmap-only SFNTs like `NotoColorEmoji.ttf' don't contain
+ entries in the bitmap strike(s) for empty glyphs. Instead, they
+ rely that a space glyph gets created from the font's metrics data.
+ This commit makes FreeType behave accordingly.
+
+ * include/freetype/fterrdef.h (FT_Err_Missing_Bitmap): New error
+ code.
+
+ * src/sfnt/ttsbit.c (tt_sbit_decoder_load_image): Change error codes
+ to make a distinction between a missing bitmap in a composite and a
+ simple missing bitmap.
+
+ * src/truetype/ttgload.c (TT_Load_Glyph): For a missing bitmap (in a
+ bitmap-only font), synthesize an empty bitmap glyph if metrics are
+ available.
+
2017-08-10 Werner Lemberg <[email protected]>
[base] Minor API improvement for default variation axis setting.
--- a/include/freetype/fterrdef.h
+++ b/include/freetype/fterrdef.h
@@ -233,6 +233,8 @@
"invalid PostScript (post) table" )
FT_ERRORDEF_( DEF_In_Glyf_Bytecode, 0x9C,
"found FDEF or IDEF opcode in glyf bytecode" )
+ FT_ERRORDEF_( Missing_Bitmap, 0x9D,
+ "missing bitmap in strike" )
/* CFF, CID, and Type 1 errors */
--- a/src/sfnt/ttsbit.c
+++ b/src/sfnt/ttsbit.c
@@ -1448,10 +1448,17 @@
return FT_THROW( Invalid_Table );
NoBitmap:
+ if ( recurse_count )
+ {+ FT_TRACE4(( "tt_sbit_decoder_load_image:"
+ " missing subglyph sbit with glyph index %d\n",
+ glyph_index ));
+ return FT_THROW( Invalid_Composite );
+ }
+
FT_TRACE4(( "tt_sbit_decoder_load_image:"
" no sbit found for glyph index %d\n", glyph_index ));
-
- return FT_THROW( Invalid_Argument );
+ return FT_THROW( Missing_Bitmap );
}
--- a/src/truetype/ttgload.c
+++ b/src/truetype/ttgload.c
@@ -87,7 +87,7 @@
/*************************************************************************/
/* */
/* Return the vertical metrics in font units for a given glyph. */
- /* See macro `TT_LOADER_SET_PP' below for explanations. */
+ /* See function `tt_loader_set_pp' below for explanations. */
/* */
FT_LOCAL_DEF( void )
TT_Get_VMetrics( TT_Face face,
@@ -2625,7 +2625,58 @@
IS_DEFAULT_INSTANCE )
{error = load_sbit_image( size, glyph, glyph_index, load_flags );
- if ( error )
+ if ( FT_ERR_EQ( error, Missing_Bitmap ) )
+ {+ /* the bitmap strike is incomplete and misses the requested glyph; */
+ /* if we have a bitmap-only font, return an empty glyph */
+ if ( !FT_IS_SCALABLE( glyph->face ) )
+ {+ TT_Face face = (TT_Face)glyph->face;
+ FT_Short left_bearing = 0, top_bearing = 0;
+ FT_UShort advance_width = 0, advance_height = 0;
+
+
+ /* to return an empty glyph, however, we need metrics data */
+ /* from the `hmtx' (or `vmtx') table; the assumption is that */
+ /* empty glyphs are missing intentionally, representing */
+ /* whitespace - not having at least horizontal metrics is */
+ /* thus considered an error */
+ if ( !face->horz_metrics_size )
+ return error;
+
+ /* we now construct an empty bitmap glyph */
+ TT_Get_HMetrics( face, glyph_index,
+ &left_bearing,
+ &advance_width );
+ TT_Get_VMetrics( face, glyph_index,
+ 0,
+ &top_bearing,
+ &advance_height );
+
+ glyph->outline.n_points = 0;
+ glyph->outline.n_contours = 0;
+
+ glyph->metrics.width = 0;
+ glyph->metrics.height = 0;
+
+ glyph->metrics.horiBearingX = left_bearing;
+ glyph->metrics.horiBearingY = 0;
+ glyph->metrics.horiAdvance = advance_width;
+
+ glyph->metrics.vertBearingX = 0;
+ glyph->metrics.vertBearingY = top_bearing;
+ glyph->metrics.vertAdvance = advance_height;
+
+ glyph->format = FT_GLYPH_FORMAT_BITMAP;
+ glyph->bitmap.pixel_mode = FT_PIXEL_MODE_MONO;
+
+ glyph->bitmap_left = 0;
+ glyph->bitmap_top = 0;
+
+ return FT_Err_Ok;
+ }
+ }
+ else if ( error )
{/* return error if font is not scalable */
if ( !FT_IS_SCALABLE( glyph->face ) )