Use the new pixman_glyph_cache_t API that will be in pixman 0.28.0

This new pixman API allows glyphs to be cached and composited in one
go, which reduces overhead compared to individual calls to
pixman_image_composite_region32().

Notes:

- There is an explicit call to _cairo_image_scaled_glyph_fini(). This
  could instead be done with a private, but I chose not to do that
  since we don't need to store any actual data; we only need
  notification when the glyph dies.

- The slowdown in poppler-reseau is real and stable across runs. I'm
  not too concerned about it because this benchmark is only one run
  and so it is dominated by glyph cache setup costs and FreeType
  rasterizing.

Performance results, image backend:

    Speedups
       firefox-talos-gfx  5571.55 -> 4265.57:  1.31x speedup
      gnome-terminal-vim  1875.82 -> 1715.14:  1.09x speedup
               evolution  1128.24 -> 1047.68:  1.08x speedup
       xfce4-terminal-a1  1364.38 -> 1277.48:  1.07x speedup

    Slowdowns
          poppler-reseau   374.42 ->  394.29:  1.05x slowdown

Performance results, image16 backend:

    Speedups
       firefox-talos-gfx  5387.25 -> 4065.39:  1.33x speedup
      gnome-terminal-vim  2116.66 -> 1962.79:  1.08x speedup
               evolution   987.50 ->  924.27:  1.07x speedup
       xfce4-terminal-a1  1856.85 -> 1748.25:  1.06x speedup
                    gvim  1484.07 -> 1398.75:  1.06x speedup

    Slowdowns
          poppler-reseau   371.37 ->  393.99:  1.06x slowdown

Also bump pixman requirement to 0.27.1.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/cairo-scaled-font.c b/src/cairo-scaled-font.c
index fe22f54c3..8c2b64521 100644
--- a/src/cairo-scaled-font.c
+++ b/src/cairo-scaled-font.c
@@ -212,6 +212,8 @@ _cairo_scaled_glyph_fini (cairo_scaled_font_t *scaled_font,
 	private->destroy (private, scaled_glyph, scaled_font);
     }
 
+    _cairo_image_scaled_glyph_fini (scaled_font, scaled_glyph);
+    
     if (scaled_glyph->surface != NULL)
 	cairo_surface_destroy (&scaled_glyph->surface->base);