[image] Do assumption initial user data is cleared.

Benjamin Otte pointed out the error of my ways that a clear on a
cairo_image_surface_create_for_data() was not working. This is because I
modified the image surface to skip clears when it knows the target data
has been cleared. This flag must be reset when the user interacts with
the surface, such as providing the initial surface data.

1 files changed, 22 insertions, 4 deletions

diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
index 3b232006..8ad259d2 100644
--- a/src/cairo-image-surface.c
+++ b/src/cairo-image-surface.c
@@ -542,6 +542,7 @@ cairo_image_surface_create_for_data (unsigned char     *data,
 				     int		stride)
 {
     pixman_format_code_t pixman_format;
+    cairo_surface_t *surface;
     int minstride;
 
     if (! CAIRO_FORMAT_VALID (format))
@@ -562,9 +563,16 @@ cairo_image_surface_create_for_data (unsigned char     *data,
     }
 
     pixman_format = _cairo_format_to_pixman_format_code (format);
-
-    return _cairo_image_surface_create_with_pixman_format (data, pixman_format,
-							   width, height, stride);
+    surface = _cairo_image_surface_create_with_pixman_format (data,
+							      pixman_format,
+							      width, height,
+							      stride);
+    if (unlikely (surface->status))
+	return surface;
+
+    /* we can not make any assumptions by the initial state of the data */
+    ((cairo_image_surface_t *) surface)->is_clear = FALSE;
+    return surface;
 }
 slim_hidden_def (cairo_image_surface_create_for_data);
 
@@ -1610,6 +1618,16 @@ _cairo_image_surface_get_font_options (void                  *abstract_surface,
     cairo_font_options_set_hint_metrics (options, CAIRO_HINT_METRICS_ON);
 }
 
+static cairo_status_t
+_cairo_image_surface_mark_dirty_rectangle (void *abstract_surface,
+					   int x, int y,
+					   int width, int height)
+{
+    cairo_image_surface_t *surface = abstract_surface;
+    surface->is_clear = FALSE;
+    return CAIRO_STATUS_SUCCESS;
+}
+
 static cairo_int_status_t
 _cairo_image_surface_paint (void *abstract_surface,
 			    cairo_operator_t	 op,
@@ -1663,7 +1681,7 @@ const cairo_surface_backend_t _cairo_image_surface_backend = {
     NULL, /* old_show_glyphs */
     _cairo_image_surface_get_font_options,
     NULL, /* flush */
-    NULL, /* mark_dirty_rectangle */
+    _cairo_image_surface_mark_dirty_rectangle,
     NULL, /* font_fini */
     NULL, /* glyph_fini */