harfbuzz: cache glyph metrics

HarfBuzz' FreeType font functions do not cache anything and call
FT_Load_Glyph all the time, which can be slow. Add a cache for metrics
and use it with custom font functions.

1 files changed, 5 insertions, 0 deletions

diff --git a/libass/ass_cache.h b/libass/ass_cache.h
index 077e081..7375f04 100644
--- a/libass/ass_cache.h
+++ b/libass/ass_cache.h
@@ -48,6 +48,10 @@ typedef struct {
     int asc, desc;              // ascender/descender
 } OutlineHashValue;
 
+typedef struct {
+    FT_Glyph_Metrics metrics;
+} GlyphMetricsHashValue;
+
 // Create definitions for bitmap, outline and composite hash keys
 #define CREATE_STRUCT_DEFINITIONS
 #include "ass_cache_template.h"
@@ -93,6 +97,7 @@ void ass_cache_stats(Cache *cache, size_t *size, unsigned *hits,
 void ass_cache_done(Cache *cache);
 Cache *ass_font_cache_create(void);
 Cache *ass_outline_cache_create(void);
+Cache *ass_glyph_metrics_cache_create(void);
 Cache *ass_bitmap_cache_create(void);
 Cache *ass_composite_cache_create(void);