BLF: Save fixed_width value in cache

Cache the font size's ideal fixed width column size in the glyph cache
rather than the font itself to improve performance.

See D13226 for more details.

Differential Revision: https://developer.blender.org/D13226

Reviewed by Campbell Barton

1 files changed, 17 insertions, 0 deletions

diff --git a/source/blender/blenfont/intern/blf_glyph.c b/source/blender/blenfont/intern/blf_glyph.c
index b87a784adff..c8cc15e804b 100644
--- a/source/blender/blenfont/intern/blf_glyph.c
+++ b/source/blender/blenfont/intern/blf_glyph.c
@@ -34,6 +34,7 @@
 #include FT_GLYPH_H
 #include FT_OUTLINE_H
 #include FT_BITMAP_H
+#include FT_ADVANCES_H /* For FT_Get_Advance. */
 
 #include "MEM_guardedalloc.h"
 
@@ -100,6 +101,22 @@ GlyphCacheBLF *blf_glyph_cache_new(FontBLF *font)
   memset(gc->glyph_ascii_table, 0, sizeof(gc->glyph_ascii_table));
   memset(gc->bucket, 0, sizeof(gc->bucket));
 
+  /* Determine ideal fixed-width size for monospaced output. */
+  FT_UInt gindex = FT_Get_Char_Index(font->face, U'0');
+  if (gindex) {
+    FT_Fixed advance = 0;
+    FT_Get_Advance(font->face, gindex, FT_LOAD_NO_HINTING, &advance);
+    /* Use CSS 'ch unit' width, advance of zero character. */
+    gc->fixed_width = (int)(advance >> 16);
+  }
+  else {
+    /* Font does not contain "0" so use CSS fallback of 1/2 of em. */
+    gc->fixed_width = (int)((font->face->size->metrics.height / 2) >> 6);
+  }
+  if (gc->fixed_width < 1) {
+    gc->fixed_width = 1;
+  }
+
   BLI_addhead(&font->cache, gc);
   return gc;
 }