The amazing lazy-copy-back-repaint-page-flip

Always use pageflipping, but avoid full repaint by copying back dirty
regions from front to back.  Additionally, we dealy copying back until
we're ready to paint the new frame, so we can avoid copying areas that
will be repainted anyway.

This is the least amount of copying per frame we can get away with at all
and at the same time we don't have to worry about stalling the GPU on
synchronized blits since we always pageflip.

clutter/wayland/clutter-backend-wayland.c

@@ -115,8 +115,16 @@ handle_configure (void *data, struct wl_shell *shell,
 
   stage_wayland = wl_surface_get_user_data (surface);
 
+  if ((stage_wayland->allocation.width != width) ||
+      (stage_wayland->allocation.height != height))
+    {
+      clutter_actor_queue_relayout (CLUTTER_ACTOR (stage_wayland->wrapper));
+    }
+
   stage_wayland->pending_allocation.x = x;
   stage_wayland->pending_allocation.y = y;
+  stage_wayland->pending_allocation.width = width;
+  stage_wayland->pending_allocation.height = height;
   stage_wayland->allocation = stage_wayland->pending_allocation;
 
   clutter_actor_set_size (CLUTTER_ACTOR (stage_wayland->wrapper),

clutter/wayland/clutter-stage-wayland.c

@@ -77,7 +77,10 @@ wayland_create_buffer (ClutterStageWayland *stage_wayland,
       EGL_DRM_BUFFER_USE_MESA, EGL_DRM_BUFFER_USE_SCANOUT_MESA,
       EGL_NONE
   };
-  CoglHandle tex;
+  struct wl_visual *visual;
+  EGLint name;
+  EGLint stride;
+  cairo_rectangle_int_t rect;
 
   buffer = g_slice_new (ClutterStageWaylandWaylandBuffer);
 
@@ -88,16 +91,31 @@ wayland_create_buffer (ClutterStageWayland *stage_wayland,
   glBindTexture (GL_TEXTURE_2D, buffer->texture);
   backend_wayland->image_target_texture_2d (GL_TEXTURE_2D, buffer->drm_image);
 
-  tex = cogl_texture_new_from_foreign (buffer->texture,
+  buffer->tex = cogl_texture_new_from_foreign (buffer->texture,
-                                       GL_TEXTURE_2D,
+					       GL_TEXTURE_2D,
-                                       geom->width,
+					       geom->width,
-                                       geom->height,
+					       geom->height,
-                                       0,
+					       0,
-                                       0,
+					       0,
-                                       COGL_PIXEL_FORMAT_ARGB_8888);
+					       COGL_PIXEL_FORMAT_ARGB_8888);
-  buffer->offscreen = cogl_offscreen_new_to_texture (tex);
+  buffer->offscreen = cogl_offscreen_new_to_texture (buffer->tex);
-  cogl_handle_unref (tex);
+
-  buffer->wayland_buffer = NULL;
+  backend_wayland->export_drm_image (edpy, buffer->drm_image,
+				     &name, NULL, &stride);
+  visual =
+    wl_display_get_premultiplied_argb_visual (backend_wayland->wayland_display);
+  buffer->wayland_buffer =
+    wl_drm_create_buffer (backend_wayland->wayland_drm,
+                          name,
+                          stage_wayland->allocation.width,
+                          stage_wayland->allocation.height,
+                          stride, visual);
+
+  rect.x = geom->x;
+  rect.y = geom->y;
+  rect.width = geom->width;
+  rect.height = geom->height;
+  buffer->dirty_region = cairo_region_create_rectangle (&rect);
 
   return buffer;
 }
@@ -109,9 +127,8 @@ wayland_free_buffer (ClutterStageWaylandWaylandBuffer *buffer)
   ClutterBackendWayland *backend_wayland = CLUTTER_BACKEND_WAYLAND (backend);
   EGLDisplay edpy = clutter_egl_display ();
 
-  if (buffer->wayland_buffer)
+  cogl_handle_unref (buffer->tex);
-    wl_buffer_destroy (buffer->wayland_buffer);
+  wl_buffer_destroy (buffer->wayland_buffer);
-
   cogl_handle_unref (buffer->offscreen);
   glDeleteTextures (1, &buffer->texture);
   backend_wayland->destroy_image (edpy, buffer->drm_image);
@@ -235,9 +252,61 @@ clutter_stage_wayland_resize (ClutterStageWindow *stage_window,
 			      gint                height)
 {
   ClutterStageWayland *stage_wayland = CLUTTER_STAGE_WAYLAND (stage_window);
+  cairo_rectangle_int_t rect;
+
+  fprintf (stderr, "resize %dx%d\n", width, height);
 
   stage_wayland->pending_allocation.width = width;
   stage_wayland->pending_allocation.height = height;
+
+  /* FIXME: Shouldn't the stage repaint everything when it gets resized? */
+  rect.x = stage_wayland->pending_allocation.x;
+  rect.y = stage_wayland->pending_allocation.y;
+  rect.width = stage_wayland->pending_allocation.width;
+  rect.height = stage_wayland->pending_allocation.height;
+  cairo_region_union_rectangle (stage_wayland->repaint_region, &rect);
+}
+
+#define CAIRO_REGION_FULL ((cairo_region_t *) 1)
+
+static gboolean
+clutter_stage_wayland_has_redraw_clips (ClutterStageWindow *stage_window)
+{
+  return TRUE;
+}
+
+static gboolean
+clutter_stage_wayland_ignoring_redraw_clips (ClutterStageWindow *stage_window)
+{
+  return FALSE;
+}
+
+static void
+clutter_stage_wayland_add_redraw_clip (ClutterStageWindow *stage_window,
+				       ClutterGeometry    *stage_clip)
+{
+  ClutterStageWayland *stage_wayland = CLUTTER_STAGE_WAYLAND (stage_window);
+  cairo_rectangle_int_t rect;
+
+  if (stage_clip == NULL)
+    {
+      rect.x = stage_wayland->allocation.x;
+      rect.y = stage_wayland->allocation.y;
+      rect.width = stage_wayland->allocation.width;
+      rect.height = stage_wayland->allocation.height;
+    }
+  else
+    {
+      rect.x = stage_clip->x;
+      rect.y = stage_clip->y;
+      rect.width = stage_clip->width;
+      rect.height = stage_clip->height;
+    }
+
+  if (stage_wayland->repaint_region == NULL)
+    stage_wayland->repaint_region = cairo_region_create_rectangle (&rect);
+  else
+    cairo_region_union_rectangle (stage_wayland->repaint_region, &rect);
 }
 
 static void
@@ -254,6 +323,10 @@ clutter_stage_window_iface_init (ClutterStageWindowIface *iface)
   iface->resize = clutter_stage_wayland_resize;
   iface->show = clutter_stage_wayland_show;
   iface->hide = clutter_stage_wayland_hide;
+
+  iface->add_redraw_clip = clutter_stage_wayland_add_redraw_clip;
+  iface->has_redraw_clips = clutter_stage_wayland_has_redraw_clips;
+  iface->ignoring_redraw_clips = clutter_stage_wayland_ignoring_redraw_clips;
 }
 
 static void
@@ -271,20 +344,6 @@ _clutter_stage_wayland_init (ClutterStageWayland *stage_wayland)
   stage_wayland->save_allocation = stage_wayland->allocation;
 }
 
-static void
-wayland_free_front_buffer (void *data)
-{
-  ClutterStageWayland *stage_wayland = data;
-
-  if (stage_wayland->front_buffer)
-    wayland_free_buffer (stage_wayland->front_buffer);
-  stage_wayland->front_buffer = stage_wayland->pending_buffer;
-  stage_wayland->pending_buffer = NULL;
-
-  if (stage_wayland->back_buffer)
-    wayland_swap_buffers (stage_wayland);
-}
-
 static void
 wayland_frame_callback (void *data, uint32_t _time)
 {
@@ -298,38 +357,19 @@ wayland_swap_buffers (ClutterStageWayland *stage_wayland)
 {
   ClutterBackend *backend = clutter_get_default_backend ();
   ClutterBackendWayland *backend_wayland = CLUTTER_BACKEND_WAYLAND (backend);
-  EGLDisplay edpy = clutter_egl_display ();
+  ClutterStageWaylandWaylandBuffer *buffer;
-  EGLint name;
-  EGLint stride;
-  struct wl_visual *visual;
 
-  if (stage_wayland->pending_buffer)
+  buffer = stage_wayland->front_buffer;
-    return;
+  stage_wayland->front_buffer = stage_wayland->back_buffer;
+  stage_wayland->back_buffer = buffer;
 
-  stage_wayland->pending_buffer = stage_wayland->back_buffer;
-  stage_wayland->back_buffer = NULL;
-
-  backend_wayland->export_drm_image (edpy,
-				     stage_wayland->pending_buffer->drm_image,
-				     &name, NULL, &stride);
-  visual =
-    wl_display_get_premultiplied_argb_visual (backend_wayland->wayland_display);
-  stage_wayland->pending_buffer->wayland_buffer =
-    wl_drm_create_buffer (backend_wayland->wayland_drm,
-                          name,
-                          stage_wayland->allocation.width,
-                          stage_wayland->allocation.height,
-                          stride, visual);
   wl_surface_attach (stage_wayland->wayland_surface,
-                     stage_wayland->pending_buffer->wayland_buffer);
+                     stage_wayland->front_buffer->wayland_buffer);
   wl_surface_map (stage_wayland->wayland_surface,
                   stage_wayland->allocation.x,
                   stage_wayland->allocation.y,
                   stage_wayland->allocation.width,
                   stage_wayland->allocation.height);
-  wl_display_sync_callback (backend_wayland->wayland_display,
-                            wayland_free_front_buffer,
-                            stage_wayland);
 
   stage_wayland->pending_swaps++;
   wl_display_frame_callback (backend_wayland->wayland_display,
@@ -337,32 +377,157 @@ wayland_swap_buffers (ClutterStageWayland *stage_wayland)
 			     stage_wayland);
 }
 
+static void
+_clutter_stage_wayland_repair_dirty(ClutterStageWayland *stage_wayland,
+				       ClutterStage     *stage)
+{
+  CoglMaterial *outline = NULL;
+  CoglHandle vbo;
+  float vertices[8], texcoords[8];
+  CoglMatrix modelview;
+  cairo_region_t *dirty;
+  cairo_rectangle_int_t rect;
+  int i, count;
+  float width, height;
+
+  dirty = stage_wayland->back_buffer->dirty_region;
+  stage_wayland->back_buffer->dirty_region = NULL;
+  cairo_region_subtract (dirty, stage_wayland->repaint_region);
+  width = stage_wayland->allocation.width;
+  height = stage_wayland->allocation.height;
+  
+  /* If this is the first time we render, there is no front buffer to
+   * copy back from, but then the dirty region not covered by the
+   * repaint should be empty, because we repaint the entire stage.
+   *
+   * assert(stage_wayland->front_buffer != NULL) ||
+   *   cairo_region_is_empty(dirty);
+   *
+   * FIXME: in test-rotate, the stage never queues a full repaint
+   * initially, it's restricted to the paint box of it's rotating
+   * children.
+   */
+
+  if (!stage_wayland->front_buffer)
+    return;
+
+  outline = cogl_material_new ();
+  cogl_material_set_layer (outline, 0, stage_wayland->front_buffer->tex);
+  count = cairo_region_num_rectangles (dirty);
+
+  for (i = 0; i < count; i++)
+    {
+      cairo_region_get_rectangle (dirty, i, &rect);
+      vbo = cogl_vertex_buffer_new (4);
+
+      vertices[0] = rect.x - 1;
+      vertices[1] = rect.y - 1;
+      vertices[2] = rect.x + rect.width + 1;
+      vertices[3] = rect.y - 1;
+      vertices[4] = rect.x + rect.width + 1;
+      vertices[5] = rect.y + rect.height + 1;
+      vertices[6] = rect.x - 1;
+      vertices[7] = rect.y + rect.height + 1;
+
+      cogl_vertex_buffer_add (vbo,
+			      "gl_Vertex",
+			      2, /* n_components */
+			      COGL_ATTRIBUTE_TYPE_FLOAT,
+			      FALSE, /* normalized */
+			      0, /* stride */
+			      vertices);
+
+      texcoords[0] = vertices[0] / width;
+      texcoords[1] = vertices[1] / height;
+      texcoords[2] = vertices[2] / width;
+      texcoords[3] = vertices[3] / height;
+      texcoords[4] = vertices[4] / width;
+      texcoords[5] = vertices[5] / height;
+      texcoords[6] = vertices[6] / width;
+      texcoords[7] = vertices[7] / height;
+
+      cogl_vertex_buffer_add (vbo,
+			      "gl_MultiTexCoord0",
+			      2, /* n_components */
+			      COGL_ATTRIBUTE_TYPE_FLOAT,
+			      FALSE, /* normalized */
+			      0, /* stride */
+			      texcoords);
+
+      cogl_vertex_buffer_submit (vbo);
+
+      cogl_push_matrix ();
+      cogl_matrix_init_identity (&modelview);
+      _clutter_actor_apply_modelview_transform (CLUTTER_ACTOR (stage),
+						&modelview);
+      cogl_set_modelview_matrix (&modelview);
+      cogl_set_source (outline);
+      cogl_vertex_buffer_draw (vbo, COGL_VERTICES_MODE_TRIANGLE_FAN,
+			       0 , 4);
+      cogl_pop_matrix ();
+      cogl_object_unref (vbo);
+    }
+
+  cairo_region_destroy (dirty);
+}
+
+void
+_clutter_stage_wayland_repaint_region (ClutterStageWayland *stage_wayland,
+				       ClutterStage        *stage)
+{
+  ClutterGeometry geom;
+  cairo_rectangle_int_t rect;
+  int i, count;
+
+  count = cairo_region_num_rectangles (stage_wayland->repaint_region);
+  for (i = 0; i < count; i++)
+    {
+      cairo_region_get_rectangle (stage_wayland->repaint_region, i, &rect);
+
+      cogl_clip_push_window_rectangle (rect.x - 1, rect.y - 1,
+				       rect.width + 2, rect.height + 2);
+
+      geom.x = rect.x;
+      geom.y = rect.y;
+      geom.width = rect.width;
+      geom.height = rect.height;
+      /* FIXME: We should pass geom in as second arg, but some actors
+       * cull themselves a little to much.  Disable for now.*/
+      _clutter_stage_do_paint (stage, NULL);
+
+      cogl_clip_pop ();
+    }
+}
+
 void
 _clutter_stage_wayland_redraw (ClutterStageWayland *stage_wayland,
 			       ClutterStage    *stage)
 {
-  ClutterActor *wrapper = CLUTTER_ACTOR (stage_wayland->wrapper);
-
   stage_wayland->allocation = stage_wayland->pending_allocation;
 
-  if (stage_wayland->back_buffer)
+  if (!stage_wayland->back_buffer)
-    {
+      stage_wayland->back_buffer =
-      wayland_free_buffer (stage_wayland->back_buffer);
+	wayland_create_buffer (stage_wayland, &stage_wayland->allocation);
-      stage_wayland->back_buffer = NULL;
-    }
-
-  stage_wayland->back_buffer = wayland_create_buffer (stage_wayland,
-                                                  &stage_wayland->allocation);
 
   cogl_set_framebuffer (stage_wayland->back_buffer->offscreen);
   _clutter_stage_maybe_setup_viewport (stage_wayland->wrapper);
 
-  clutter_actor_paint (wrapper);
+  _clutter_stage_wayland_repair_dirty (stage_wayland, stage);
+
+  _clutter_stage_wayland_repaint_region (stage_wayland, stage);
+
   cogl_flush ();
   glFlush ();
 
+  wayland_swap_buffers (stage_wayland);
+
+  if (stage_wayland->back_buffer)
+    stage_wayland->back_buffer->dirty_region = stage_wayland->repaint_region;
+  else
+    cairo_region_destroy (stage_wayland->repaint_region);
+
+  stage_wayland->repaint_region = NULL;
+
   cogl_set_framebuffer (stage_wayland->pick_buffer->offscreen);
   _clutter_stage_maybe_setup_viewport (stage_wayland->wrapper);
-
-  wayland_swap_buffers (stage_wayland);
 }

clutter/wayland/clutter-stage-wayland.h

@@ -57,6 +57,8 @@ typedef struct _ClutterStageWaylandWaylandBuffer
   GLuint texture;
   CoglHandle offscreen;
   struct wl_buffer *wayland_buffer;
+  cairo_region_t *dirty_region;
+  CoglHandle tex;
 } ClutterStageWaylandWaylandBuffer;
 
 struct _ClutterStageWayland
@@ -77,8 +79,8 @@ struct _ClutterStageWayland
 
   ClutterStageWaylandWaylandBuffer *front_buffer;
   ClutterStageWaylandWaylandBuffer *back_buffer;
-  ClutterStageWaylandWaylandBuffer *pending_buffer;
   ClutterStageWaylandWaylandBuffer *pick_buffer;
+  cairo_region_t *repaint_region;
 };
 
 struct _ClutterStageWaylandClass