[gtk/better-glyph-caching] ngl: Improve glyph caching

[Matthias Clasen <matthiasc src gnome org>]

commit bc088d668340b2b02cd4c97d158cd944dea238ea
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu May 13 21:35:26 2021 -0400

    ngl: Improve glyph caching
    
    Avoid creating duplicate cache entries with miniscule
    scale differences. It does not cost us much to use a
    slightly larger texture for a glyph.

 gsk/ngl/gsknglrenderjob.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/gsk/ngl/gsknglrenderjob.c b/gsk/ngl/gsknglrenderjob.c
index d08d45a04f..0ebe3921cb 100644
--- a/gsk/ngl/gsknglrenderjob.c
+++ b/gsk/ngl/gsknglrenderjob.c
@@ -2837,6 +2837,7 @@ gsk_ngl_render_job_visit_text_node (GskNglRenderJob     *job,
   guint i;
   int yshift;
   float ypos;
+  float scale;
 
   if (num_glyphs == 0)
     return;
@@ -2847,8 +2848,13 @@ gsk_ngl_render_job_visit_text_node (GskNglRenderJob     *job,
   if (force_color || !gsk_text_node_has_color_glyphs (node))
     rgba_to_half (color, c);
 
+  /* Avoid caching glyphs with miniscule scale differences */
+  scale = 1;
+  while (scale < text_scale)
+    scale *= 1.2;
+
   lookup.font = (PangoFont *)font;
-  lookup.scale = (guint) (text_scale * 1024);
+  lookup.scale = (guint) (scale * 1024);
 
   yshift = compute_phase_and_pos (y, &ypos);