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[subset] add helper methods to glyf accelerator for reading composite glyph information.

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This commit is contained in:
Garret Rieger 2018-02-15 14:03:34 -08:00 committed by Behdad Esfahbod
parent 926db87455
commit d368414143
1 changed files with 112 additions and 3 deletions
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115
src/hb-ot-glyf-table.hh
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@ -81,9 +81,9 @@ struct glyf
struct GlyphHeader
{
HBINT16 numberOfContours; /* If the number of contours is
* greater than or equal to zero,
* this is a simple glyph; if negative,
* this is a composite glyph. */
* greater than or equal to zero,
* this is a simple glyph; if negative,
* this is a composite glyph. */
FWORD xMin; /* Minimum x for coordinate data. */
FWORD yMin; /* Minimum y for coordinate data. */
FWORD xMax; /* Maximum x for coordinate data. */
@ -92,6 +92,50 @@ struct glyf
DEFINE_SIZE_STATIC (10);
};
struct CompositeGlyphHeader
{
static const uint16_t ARG_1_AND_2_ARE_WORDS = 0x0001;
static const uint16_t ARGS_ARE_XY_VALUES = 0x0002;
static const uint16_t ROUND_XY_TO_GRID = 0x0004;
static const uint16_t WE_HAVE_A_SCALE = 0x0008;
static const uint16_t MORE_COMPONENTS = 0x0020;
static const uint16_t WE_HAVE_AN_X_AND_Y_SCALE = 0x0040;
static const uint16_t WE_HAVE_A_TWO_BY_TWO = 0x0080;
static const uint16_t WE_HAVE_INSTRUCTIONS = 0x0100;
static const uint16_t USE_MY_METRICS = 0x0200;
static const uint16_t OVERLAP_COMPOUND = 0x0400;
static const uint16_t SCALED_COMPONENT_OFFSET = 0x0800;
static const uint16_t UNSCALED_COMPONENT_OFFSET = 0x1000;
HBUINT16 flags;
HBUINT16 glyphIndex;
inline unsigned int get_size (void) const
{
unsigned int size = min_size;
if (flags & ARG_1_AND_2_ARE_WORDS) {
// arg1 and 2 are int16
size += 4;
} else {
// arg1 and 2 are int8
size += 2;
}
if (flags & WE_HAVE_A_SCALE) {
// One x 16 bit (scale)
size += 2;
} else if (flags & WE_HAVE_AN_X_AND_Y_SCALE) {
// Two x 16 bit (xscale, yscale)
size += 4;
} else if (flags & WE_HAVE_A_TWO_BY_TWO) {
// Four x 16 bit (xscale, scale01, scale10, yscale)
size += 8;
}
return size;
}
DEFINE_SIZE_MIN (4);
};
struct accelerator_t
{
inline void init (hb_face_t *face)
@ -122,6 +166,71 @@ struct glyf
hb_blob_destroy (glyf_blob);
}
inline bool in_table (const char *offset, unsigned int len) const
{
return (offset - (const char *) glyf_table + len) <= glyf_len;
}
inline bool in_table (const CompositeGlyphHeader *header) const
{
return in_table ((const char *) header, CompositeGlyphHeader::min_size)
&& in_table ((const char *) header, header->get_size());
}
inline bool in_glyph (const CompositeGlyphHeader *header,
unsigned int start_offset,
unsigned int end_offset)
{
do
{
unsigned int offset_in_glyf = (const char *) header - (const char*) glyf_table;
if (offset_in_glyf < start_offset
|| offset_in_glyf + header->get_size() > end_offset)
return false;
} while (next_composite (&header));
return true;
}
/*
* Returns true if the referenced glyph is a valid glyph and a composite glyph.
* If true is returned a pointer to the composite glyph will be written into
* composite.
*/
inline bool get_composite (hb_codepoint_t glyph, const CompositeGlyphHeader ** composite /* OUT */)
{
unsigned int start_offset, end_offset;
if (!get_offsets (glyph, &start_offset, &end_offset))
return false; /* glyph not found */
if (end_offset - start_offset < GlyphHeader::static_size)
return false; /* Empty glyph; zero extents. */
const GlyphHeader &glyph_header = StructAtOffset<GlyphHeader> (glyf_table, start_offset);
if (glyph_header.numberOfContours < 0) {
const CompositeGlyphHeader *possible = &StructAfter<CompositeGlyphHeader, GlyphHeader> (glyph_header);
if (!in_table (possible)
|| !in_glyph (possible, start_offset, end_offset))
return false;
*composite = possible;
return true;
}
return false;
}
inline bool next_composite (const CompositeGlyphHeader ** next /* IN/OUT */) const
{
if ((*next)->flags & CompositeGlyphHeader::MORE_COMPONENTS)
{
const CompositeGlyphHeader *possible = &StructAfter<CompositeGlyphHeader, CompositeGlyphHeader> (**next);
if (!in_table (possible))
return false;
*next = possible;
return true;
}
return false;
}
inline bool get_offsets (hb_codepoint_t glyph,
unsigned int *start_offset /* OUT */,
unsigned int *end_offset /* OUT */) const