[cairo-pattern] Cache surface for solid patterns

We use a small cache of size 16 for surfaces created for solid patterns.
This mainly helps with the X backends where we don't have to create a
pattern for every operation, so we save a lot on X traffic.  Xft uses a
similar cache, so cairo's text rendering traffic with the xlib backend
now completely matches that of Xft.

The cache uses an static index variable, which itself acts like a cache of
size 1, remembering the most recently used solid pattern.  So repeated
lookups for the same pattern hit immediately.  If that fails, the cache is
searched linearly, and if that fails too, a new surface is created and a
random member of the cache is evicted.

Only surfaces that are "compatible" are used.  The definition of compatible
is backend specific.  For the xlib backend, it means that the two surfaces
are allocated on the same display.  Implementations for compatibility are
provided for all backends that it makes sense.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/cairo-debug.c b/src/cairo-debug.c
index 7c299325..dd57dd78 100644
--- a/src/cairo-debug.c
+++ b/src/cairo-debug.c
@@ -68,4 +68,6 @@ cairo_debug_reset_static_data (void)
 #if CAIRO_HAS_FT_FONT
     _cairo_ft_font_reset_static_data ();
 #endif
+
+    _cairo_pattern_reset_static_data ();
 }