[gtk+] gsk: Add internal Renderer.create_cairo_surface()

[Emmanuele Bassi <ebassi src gnome org>]

commit 50a5deb8e382a4c116aa383e9c932d42a19efbfb
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Mon Oct 31 16:26:50 2016 +0000

    gsk: Add internal Renderer.create_cairo_surface()
    
    We need an overridable entry point for GskRenderer to create Cairo
    surfaces.
    
    Implementations of GskRenderer can override create_cairo_surface() to
    create efficient surfaces, possibly with zero copies involved, depending
    on the GDK backend.

 gsk/gskrenderer.c        |   31 +++++++++++++++++++++++++++++++
 gsk/gskrendererprivate.h |   17 +++++++++++++----
 2 files changed, 44 insertions(+), 4 deletions(-)
---
diff --git a/gsk/gskrenderer.c b/gsk/gskrenderer.c
index 2d7cdec..21236cf 100644
--- a/gsk/gskrenderer.c
+++ b/gsk/gskrenderer.c
@@ -115,6 +115,24 @@ gsk_renderer_real_render (GskRenderer *self,
   GSK_RENDERER_WARN_NOT_IMPLEMENTED_METHOD (self, render);
 }
 
+static cairo_surface_t *
+gsk_renderer_real_create_cairo_surface (GskRenderer    *self,
+                                        cairo_format_t  format,
+                                        int             width,
+                                        int             height)
+{
+  GskRendererPrivate *priv = gsk_renderer_get_instance_private (self);
+  int scale_factor = priv->scale_factor > 0 ? priv->scale_factor : 1;
+  int real_width = width * scale_factor;
+  int real_height = height * scale_factor;
+
+  cairo_surface_t *res = cairo_image_surface_create (format, real_width, real_height);
+
+  cairo_surface_set_device_scale (res, scale_factor, scale_factor);
+
+  return res;
+}
+
 static void
 gsk_renderer_dispose (GObject *gobject)
 {
@@ -220,6 +238,7 @@ gsk_renderer_class_init (GskRendererClass *klass)
   klass->realize = gsk_renderer_real_realize;
   klass->unrealize = gsk_renderer_real_unrealize;
   klass->render = gsk_renderer_real_render;
+  klass->create_cairo_surface = gsk_renderer_real_create_cairo_surface;
 
   gobject_class->constructed = gsk_renderer_constructed;
   gobject_class->set_property = gsk_renderer_set_property;
@@ -733,6 +752,18 @@ gsk_renderer_get_for_display (GdkDisplay *display)
   return g_object_new (renderer_type, "display", display, NULL);
 }
 
+cairo_surface_t *
+gsk_renderer_create_cairo_surface (GskRenderer    *renderer,
+                                   cairo_format_t  format,
+                                   int             width,
+                                   int             height)
+{
+  g_return_val_if_fail (GSK_IS_RENDERER (renderer), NULL);
+  g_return_val_if_fail (width > 0 && height > 0, NULL);
+
+  return GSK_RENDERER_GET_CLASS (renderer)->create_cairo_surface (renderer, format, width, height);
+}
+
 static void
 gsk_renderer_set_cairo_context (GskRenderer *renderer,
                                 cairo_t     *cr)
diff --git a/gsk/gskrendererprivate.h b/gsk/gskrendererprivate.h
index d702ae5..57f7e86 100644
--- a/gsk/gskrendererprivate.h
+++ b/gsk/gskrendererprivate.h
@@ -42,15 +42,24 @@ struct _GskRendererClass
 
   void (* render) (GskRenderer *renderer,
                    GskRenderNode *root);
+
+  cairo_surface_t * (* create_cairo_surface) (GskRenderer *renderer,
+                                              cairo_format_t,
+                                              int width,
+                                              int height);
 };
 
 gboolean gsk_renderer_is_realized (GskRenderer *renderer);
 
-GskRenderNode *         gsk_renderer_get_root_node              (GskRenderer *renderer);
-GdkDrawingContext *     gsk_renderer_get_drawing_context        (GskRenderer *renderer);
-cairo_t *               gsk_renderer_get_cairo_context          (GskRenderer *renderer);
+GskRenderNode *         gsk_renderer_get_root_node              (GskRenderer    *renderer);
+GdkDrawingContext *     gsk_renderer_get_drawing_context        (GskRenderer    *renderer);
+cairo_t *               gsk_renderer_get_cairo_context          (GskRenderer    *renderer);
+cairo_surface_t *       gsk_renderer_create_cairo_surface       (GskRenderer    *renderer,
+                                                                 cairo_format_t  format,
+                                                                 int             width,
+                                                                 int             height);
 
-GskProfiler *           gsk_renderer_get_profiler               (GskRenderer *renderer);
+GskProfiler *           gsk_renderer_get_profiler               (GskRenderer    *renderer);
 
 G_END_DECLS