surface: Define private map/unmap functions

Cairo backends often need to map/unmap to a raster surface but they
don't care about the pixel format, as Pixman will be doing the format
handling.

Cairo users cannot know how to access the raw data if the format is
invalid.

The two different scenarios call for different guarantees on the
returned surface.

The private map/unmap functions also makes it possible to simply
return the status upon unmapping.

1 files changed, 41 insertions, 0 deletions

diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
index 98f70c585..00369b61a 100644
--- a/src/cairo-image-surface.c
+++ b/src/cairo-image-surface.c
@@ -1202,3 +1202,44 @@ _cairo_image_analyze_color (cairo_image_surface_t      *image)
 
     return image->color = CAIRO_IMAGE_IS_COLOR;
 }
+
+static const cairo_user_data_key_t clone_key;
+
+cairo_image_surface_t *
+_cairo_image_surface_clone_subimage (cairo_surface_t             *surface,
+				     const cairo_rectangle_int_t *extents)
+{
+    cairo_surface_t *image;
+    cairo_surface_pattern_t pattern;
+    cairo_status_t ignored;
+
+    image = cairo_surface_create_similar_image (surface,
+						_cairo_format_from_content (surface->content),
+						extents->width,
+						extents->height);
+    /* TODO: check me with non-identity device_transform. Should we
+     * clone the scaling, too? */
+    cairo_surface_set_device_offset (image,
+				     -extents->x,
+				     -extents->y);
+
+    _cairo_pattern_init_for_surface (&pattern, surface);
+    pattern.base.filter = CAIRO_FILTER_NEAREST;
+
+    ignored = _cairo_surface_paint (image,
+				    CAIRO_OPERATOR_SOURCE,
+				    &pattern.base,
+				    NULL);
+
+    _cairo_pattern_fini (&pattern.base);
+
+    cairo_surface_set_user_data (image, &clone_key, surface, NULL);
+
+    return (cairo_image_surface_t *) image;
+}
+
+cairo_bool_t
+_cairo_image_surface_is_clone (cairo_image_surface_t *image)
+{
+    return cairo_surface_get_user_data (&image->base, &clone_key) != NULL;
+}