[quartz] Snapshot CGBitmapContext-mapped surfaces to cache CGImages.

Motivation: Avoid need to recreate CGImages for unchanged surfaces,
an expensive operation, while ensuring that the CGImages are properly
freed and new ones created when the surface does change.

Thanks to Uli Schlacter for suggestion and coding guidance.

1 files changed, 76 insertions, 4 deletions

diff --git a/src/cairo-quartz-surface.c b/src/cairo-quartz-surface.c
index a92c8fed3..973c5d1a5 100644
--- a/src/cairo-quartz-surface.c
+++ b/src/cairo-quartz-surface.c
@@ -133,6 +133,21 @@ static void quartz_surface_to_png (cairo_quartz_surface_t *nq, char *dest);
 static void quartz_image_to_png (CGImageRef, char *dest);
 #endif
 
+typedef struct
+{
+    cairo_surface_t base;
+    CGImageRef image;
+} cairo_quartz_snapshot_t;
+
+static cairo_surface_t* _cairo_quartz_snapshot_create (cairo_quartz_surface_t *surface);
+static cairo_status_t _cairo_quartz_snapshot_finish (void* surface);
+static CGImageRef _cairo_quartz_surface_snapshot_get_image (cairo_quartz_surface_t *surface);
+
+static const cairo_surface_backend_t cairo_quartz_snapshot_backend = {
+    CAIRO_INTERNAL_SURFACE_TYPE_QUARTZ_SNAPSHOT,
+    _cairo_quartz_snapshot_finish,
+};
+
 static cairo_quartz_surface_t *
 _cairo_quartz_surface_create_internal (CGContextRef cgContext,
 				       cairo_content_t content,
@@ -202,6 +217,8 @@ CairoQuartzCreateCGImage (cairo_format_t format,
 
 	case CAIRO_FORMAT_RGB30:
 	case CAIRO_FORMAT_RGB16_565:
+        case CAIRO_FORMAT_RGB96F:
+        case CAIRO_FORMAT_RGBA128F:
 	case CAIRO_FORMAT_INVALID:
 	default:
 	    return NULL;
@@ -810,10 +827,12 @@ _cairo_surface_to_cgimage (cairo_surface_t       *source,
 	}
 
 	if (_cairo_quartz_is_cgcontext_bitmap_context (surface->cgContext)) {
-	    *image_out = CGBitmapContextCreateImage (surface->cgContext);
-	    if (*image_out)
-		return CAIRO_STATUS_SUCCESS;
+	    *image_out = _cairo_quartz_surface_snapshot_get_image (surface);
+	    return CAIRO_STATUS_SUCCESS;
 	}
+
+	*image_out = NULL;
+	return CAIRO_STATUS_SURFACE_TYPE_MISMATCH;
     }
 
     if (source->type == CAIRO_SURFACE_TYPE_RECORDING) {
@@ -2207,7 +2226,7 @@ _cairo_quartz_surface_clipper_intersect_clip_path (cairo_surface_clipper_t *clip
 
 // XXXtodo implement show_page; need to figure out how to handle begin/end
 
-static const struct _cairo_surface_backend cairo_quartz_surface_backend = {
+static const cairo_surface_backend_t cairo_quartz_surface_backend = {
     CAIRO_SURFACE_TYPE_QUARTZ,
     _cairo_quartz_surface_finish,
 
@@ -2238,6 +2257,10 @@ static const struct _cairo_surface_backend cairo_quartz_surface_backend = {
     _cairo_quartz_surface_fill,
     NULL,  /* fill-stroke */
     _cairo_quartz_surface_glyphs,
+    NULL, /* has_show_text_glyphs */
+    NULL, /* show_text_glyphs */
+    NULL, /* get_supported_mime_types */
+    NULL, /* tag */
 };
 
 cairo_quartz_surface_t *
@@ -2489,6 +2512,55 @@ _cairo_surface_is_quartz (const cairo_surface_t *surface)
     return surface->backend == &cairo_quartz_surface_backend;
 }
 
+cairo_surface_t*
+_cairo_quartz_snapshot_create (cairo_quartz_surface_t *surface)
+{
+    cairo_quartz_snapshot_t *snapshot = NULL;
+
+    if (!surface || !_cairo_surface_is_quartz (&surface->base) || IS_EMPTY (surface) ||
+	! _cairo_quartz_is_cgcontext_bitmap_context (surface->cgContext))
+	return NULL;
+
+    snapshot = _cairo_malloc (sizeof (cairo_quartz_snapshot_t));
+
+    if (unlikely (surface == NULL))
+	return _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_NO_MEMORY));
+
+    memset (snapshot, 0, sizeof (cairo_quartz_snapshot_t));
+    _cairo_surface_init (&snapshot->base,
+			 &cairo_quartz_snapshot_backend,
+			 NULL, CAIRO_CONTENT_COLOR_ALPHA, FALSE);
+    snapshot->image = CGBitmapContextCreateImage (surface->cgContext);
+
+    return &snapshot->base;
+}
+
+cairo_status_t
+_cairo_quartz_snapshot_finish (void *surface)
+{
+    cairo_quartz_snapshot_t *snapshot = (cairo_quartz_snapshot_t *)surface;
+   if (snapshot->image)
+	CGImageRelease (snapshot->image);
+    return CAIRO_STATUS_SUCCESS;
+}
+
+CGImageRef
+_cairo_quartz_surface_snapshot_get_image (cairo_quartz_surface_t *surface)
+{
+    cairo_surface_t *snapshot =
+	_cairo_surface_has_snapshot (&surface->base, &cairo_quartz_snapshot_backend);
+
+    if (unlikely (!snapshot))
+    {
+	snapshot = _cairo_quartz_snapshot_create (surface);
+	if (unlikely (!snapshot || cairo_surface_status (snapshot)))
+	    return NULL;
+	_cairo_surface_attach_snapshot (&surface->base, snapshot, NULL);
+    }
+
+    return CGImageRetain (((cairo_quartz_snapshot_t*)snapshot)->image);
+}
+
 /* Debug stuff */
 
 #ifdef QUARTZ_DEBUG