Add a generic cow-snapshotting framework

Provide a mechanism for backends to attach and remove snapshots. This can
be used by backends to provide a cache for _cairo_surface_clone_similar(),
or by the meta-surfaces to only emit a single pattern for each unique
snapshot.

In order to prevent stale data being returned upon a snapshot operation,
if the surface is modified (via the 5 high level operations, and on
notification of external modification) we break the association with any
current snapshot of the surface and thus preserve the current data for
their use.

1 files changed, 11 insertions, 1 deletions

diff --git a/test/mask.c b/test/mask.c
index bc1adfdb..451054e3 100644
--- a/test/mask.c
+++ b/test/mask.c
@@ -33,6 +33,7 @@
 #define PAD 2
 
 static const char *png_filename = "romedalen.png";
+static cairo_surface_t *image;
 
 static void
 set_solid_pattern (const cairo_test_context_t *ctx, cairo_t *cr, int x, int y)
@@ -64,7 +65,13 @@ set_image_pattern (const cairo_test_context_t *ctx, cairo_t *cr, int x, int y)
 {
     cairo_pattern_t *pattern;
 
-    pattern = cairo_test_create_pattern_from_png (ctx, png_filename);
+    if (image == NULL || cairo_surface_status (image)) {
+	cairo_surface_destroy (image);
+	image = cairo_test_create_surface_from_png (ctx, png_filename);
+    }
+
+    pattern = cairo_pattern_create_for_surface (image);
+    cairo_pattern_set_extend (pattern, CAIRO_EXTEND_REPEAT);
     cairo_set_source (cr, pattern);
     cairo_pattern_destroy (pattern);
 }
@@ -225,6 +232,9 @@ draw (cairo_t *cr, int width, int height)
 
     cairo_destroy (cr2);
 
+    cairo_surface_destroy (image);
+    image = NULL;
+
     return CAIRO_TEST_SUCCESS;
 }