Cache solid patterns

We use a small cache of size 16 for patterns created from solid colors,
e.g. cairo_set_source_rgb(). This helps with toolkits that draw many
widgets using the same colour scheme.

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

7 files changed, 163 insertions, 2 deletions

diff --git a/src/cairo-color.c b/src/cairo-color.c
index ad6316e1..257f8d26 100644
--- a/src/cairo-color.c
+++ b/src/cairo-color.c
@@ -160,3 +160,10 @@ _cairo_color_get_rgba_premultiplied (cairo_color_t *color,
     *blue  = color->blue  * color->alpha;
     *alpha = color->alpha;
 }
+
+cairo_bool_t
+_cairo_color_equal (const cairo_color_t *color_a,
+	            const cairo_color_t *color_b)
+{
+    return memcmp (color_a, color_b, sizeof (cairo_color_t)) == 0;
+}
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 ();
 }
diff --git a/src/cairo-mutex-list.h b/src/cairo-mutex-list.h
index 7c7bf8f8..c054e11a 100644
--- a/src/cairo-mutex-list.h
+++ b/src/cairo-mutex-list.h
@@ -34,6 +34,8 @@
 #ifndef CAIRO_MUTEX_LIST_H
 #define CAIRO_MUTEX_LIST_H
 
+CAIRO_MUTEX_DECLARE (_cairo_pattern_solid_cache_lock);
+
 CAIRO_MUTEX_DECLARE (_cairo_font_face_mutex);
 CAIRO_MUTEX_DECLARE (_cairo_scaled_font_map_mutex);
 
diff --git a/src/cairo-pattern.c b/src/cairo-pattern.c
index 26390711..6ebe0cab 100644
--- a/src/cairo-pattern.c
+++ b/src/cairo-pattern.c
@@ -259,18 +259,77 @@ _cairo_pattern_init_radial (cairo_radial_pattern_t *pattern,
     pattern->gradient.c2.radius = _cairo_fixed_from_double (fabs (radius1));
 }
 
+/* We use a small cache here, because we don't want to constantly
+ * reallocate simple colors. */
+#define MAX_PATTERN_CACHE_SIZE 16
+static struct {
+    struct {
+	cairo_color_t          color;
+	cairo_solid_pattern_t *pattern;
+    } cache[MAX_PATTERN_CACHE_SIZE];
+    int size;
+} solid_pattern_cache;
+
 cairo_pattern_t *
 _cairo_pattern_create_solid (const cairo_color_t *color)
 {
-    cairo_solid_pattern_t *pattern;
+    static int cache_index;
+    void *pattern;
+
+    CAIRO_MUTEX_LOCK (_cairo_pattern_solid_cache_lock);
+
+    /* Check cache first. */
+    if (cache_index < solid_pattern_cache.size &&
+	    _cairo_color_equal (
+		&solid_pattern_cache.cache[cache_index].color, color))
+	goto DONE;
 
+    for (cache_index = 0; cache_index < solid_pattern_cache.size; cache_index++)
+	if (_cairo_color_equal (
+		    &solid_pattern_cache.cache[cache_index].color, color))
+	    goto DONE;
+
+    /* Not cached, need to create a new pattern. */
     pattern = malloc (sizeof (cairo_solid_pattern_t));
     if (pattern == NULL)
 	return (cairo_pattern_t *) &cairo_pattern_nil.base;
 
     _cairo_pattern_init_solid (pattern, color);
 
-    return &pattern->base;
+    /* And insert it into the cache. */
+    if (solid_pattern_cache.size < MAX_PATTERN_CACHE_SIZE) {
+	solid_pattern_cache.size ++;
+	/* cache_index == solid_pattern_cache.size */
+    } else {
+	/* Evict an old pattern. */
+	cache_index = rand () % MAX_PATTERN_CACHE_SIZE;
+	cairo_pattern_destroy (
+		&solid_pattern_cache.cache[cache_index].pattern->base);
+    }
+
+    solid_pattern_cache.cache[cache_index].color = *color;
+    solid_pattern_cache.cache[cache_index].pattern = pattern;
+
+DONE:
+    pattern = cairo_pattern_reference (
+	    &solid_pattern_cache.cache[cache_index].pattern->base);
+    CAIRO_MUTEX_UNLOCK (_cairo_pattern_solid_cache_lock);
+
+    return pattern;
+}
+
+void
+_cairo_pattern_reset_static_data (void)
+{
+    int i;
+
+    CAIRO_MUTEX_LOCK (_cairo_pattern_solid_cache_lock);
+
+    for (i = 0; i < solid_pattern_cache.size; i++)
+	cairo_pattern_destroy (&solid_pattern_cache.cache[i].pattern->base);
+    solid_pattern_cache.size = 0;
+
+    CAIRO_MUTEX_UNLOCK (_cairo_pattern_solid_cache_lock);
 }
 
 static const cairo_pattern_t *
diff --git a/src/cairoint.h b/src/cairoint.h
index 35f21175..7ce7cd1b 100755
--- a/src/cairoint.h
+++ b/src/cairoint.h
@@ -1546,6 +1546,10 @@ _cairo_color_get_rgba_premultiplied (cairo_color_t *color,
 				     double	   *blue,
 				     double	   *alpha);
 
+cairo_private cairo_bool_t
+_cairo_color_equal (const cairo_color_t *color_a,
+                    const cairo_color_t *color_b);
+
 /* cairo-font.c */
 
 cairo_private void
@@ -2407,6 +2411,9 @@ cairo_private cairo_status_t
 _cairo_pattern_get_extents (cairo_pattern_t	    *pattern,
 			    cairo_rectangle_int16_t *extents);
 
+cairo_private void
+_cairo_pattern_reset_static_data (void);
+
 cairo_private cairo_status_t
 _cairo_gstate_set_antialias (cairo_gstate_t *gstate,
 			     cairo_antialias_t antialias);
diff --git a/test/Makefile.am b/test/Makefile.am
index 11e98813..792584ef 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -86,6 +86,7 @@ self-intersecting		\
 set-source			\
 show-text-current-point		\
 skew-extreme			\
+solid-pattern-cache-stress	\
 source-clip			\
 source-clip-scale		\
 source-surface-scale-paint	\
diff --git a/test/solid-pattern-cache-stress.c b/test/solid-pattern-cache-stress.c
new file mode 100644
index 00000000..93e2f697
--- /dev/null
+++ b/test/solid-pattern-cache-stress.c
@@ -0,0 +1,83 @@
+/*
+ * Copyright ? 2007 Chris Wilson.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software
+ * and its documentation for any purpose is hereby granted without
+ * fee, provided that the above copyright notice appear in all copies
+ * and that both that copyright notice and this permission notice
+ * appear in supporting documentation, and that the name of
+ * Chris Wilson. not be used in advertising or publicity pertaining to
+ * distribution of the software without specific, written prior
+ * permission. Chris Wilson makes no representations about the
+ * suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * CHRIS WILSON DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
+ * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS, IN NO EVENT SHALL CHRIS WILSON BE LIABLE FOR ANY SPECIAL,
+ * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
+ * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+ * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Author: Chris Wilson <chris at chris-wilson.co.uk>
+ */
+
+#include "cairo-test.h"
+
+static cairo_test_draw_function_t draw;
+
+cairo_test_t test = {
+    "solid-pattern-cache-stress",
+    "Stress the solid pattern cache and ensure it behaves",
+    0, 0,
+    draw
+};
+#include <cairo.h>
+#include <stdlib.h>
+
+#define LOOPS 10
+#define NRAND 100
+
+static cairo_test_status_t
+draw (cairo_t *cr, int width, int height)
+{
+    int loop;
+    int i;
+
+    for (loop = 0; loop < LOOPS; loop++) {
+	cairo_set_source_rgb (cr, 0.0, 0.0, 0.0); /* black */
+	cairo_set_source_rgb (cr, 1.0, 0.0, 0.0); /* red */
+	cairo_set_source_rgb (cr, 0.0, 1.0, 0.0); /* green */
+	cairo_set_source_rgb (cr, 1.0, 1.0, 0.0); /* yellow */
+	cairo_set_source_rgb (cr, 0.0, 0.0, 1.0); /* blue */
+	cairo_set_source_rgb (cr, 1.0, 0.0, 1.0); /* magenta */
+	cairo_set_source_rgb (cr, 0.0, 1.0, 1.0); /* cyan */
+	cairo_set_source_rgb (cr, 1.0, 1.0, 1.0); /* white */
+
+	cairo_set_source_rgba (cr, 0.0, 0.0, 0.0, 1.0); /* black */
+	cairo_set_source_rgba (cr, 1.0, 0.0, 0.0, 1.0); /* red */
+	cairo_set_source_rgba (cr, 0.0, 1.0, 0.0, 1.0); /* green */
+	cairo_set_source_rgba (cr, 1.0, 1.0, 0.0, 1.0); /* yellow */
+	cairo_set_source_rgba (cr, 0.0, 0.0, 1.0, 1.0); /* blue */
+	cairo_set_source_rgba (cr, 1.0, 0.0, 1.0, 1.0); /* magenta */
+	cairo_set_source_rgba (cr, 0.0, 1.0, 1.0, 1.0); /* cyan */
+	cairo_set_source_rgba (cr, 1.0, 1.0, 1.0, 1.0); /* white */
+
+	for (i = 0; i < NRAND; i++)
+	    cairo_set_source_rgba (cr,
+		                   drand48 (),
+				   drand48 (),
+				   drand48 (),
+				   drand48 ());
+    }
+
+    return CAIRO_TEST_SUCCESS;
+}
+
+int
+main (void)
+{
+    return cairo_test (&test);
+}
+