[image] Clone the format for a similar surface with identical content

Honour the incoming surface format when we are asked to create a similar
surface with identical content. The goal of
cairo_surface_create_similar() is to create an intermediate with similar
characteristics to the original that can be used in place of the
original and be quick to copy to the original. Matching the format for
the same content, ensures that the blits between the two need only be a
memcpy.

1 files changed, 9 insertions, 2 deletions

diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
index 9310a517..05b0edbb 100644
--- a/src/cairo-image-surface.c
+++ b/src/cairo-image-surface.c
@@ -760,12 +760,19 @@ _cairo_format_bits_per_pixel (cairo_format_t format)
 }
 
 static cairo_surface_t *
-_cairo_image_surface_create_similar (void	       *abstract_src,
+_cairo_image_surface_create_similar (void	       *abstract_other,
 				     cairo_content_t	content,
 				     int		width,
 				     int		height)
 {
-    assert (CAIRO_CONTENT_VALID (content));
+    cairo_image_surface_t *other = abstract_other;
+
+    if (content == other->base.content) {
+	return _cairo_image_surface_create_with_pixman_format (NULL,
+							       other->pixman_format,
+							       width, height,
+							       0);
+    }
 
     return _cairo_image_surface_create_with_content (content,
 						     width, height);