debug: CLUTTER_DEBUG_REDRAWS: disable clipped redraws

This ensures that clipped redraws are disabled when using
CLUTTER_PAINT=redraws. This may seem unintuitive given that this option
is for debugging clipped redraws, but we can't draw an outline outside
the clip region and anything we draw inside the clip region is liable to
leave a trailing mess on the screen since it won't be cleared up by
later clipped redraws.

clutter/clutter-main.c

@@ -1611,6 +1611,13 @@ clutter_init_real (GError **error)
   if (!_clutter_backend_post_parse (backend, error))
     return CLUTTER_INIT_ERROR_BACKEND;
 
+  /* If we are displaying the regions that would get redrawn with clipped
+   * redraws enabled we actually have to disable the clipped redrawing
+   * because otherwise we end up with nasty trails of rectangles everywhere.
+   */
+  if (clutter_paint_debug_flags & CLUTTER_DEBUG_REDRAWS)
+    clutter_paint_debug_flags |= CLUTTER_DEBUG_DISABLE_CLIPPED_REDRAWS;
+
   /* The same is true when drawing the outlines of paint volumes... */
   if (clutter_paint_debug_flags & CLUTTER_DEBUG_PAINT_VOLUMES)
     clutter_paint_debug_flags |= CLUTTER_DEBUG_DISABLE_CLIPPED_REDRAWS;

clutter/glx/clutter-stage-glx.c

@@ -498,6 +498,8 @@ _clutter_stage_glx_redraw (ClutterStageGLX *stage_glx,
   ClutterStageX11   *stage_x11;
   GLXDrawable        drawable;
   unsigned int       video_sync_count;
+  gboolean           may_use_clipped_redraw;
+  gboolean           use_clipped_redraw;
   CLUTTER_STATIC_TIMER (painting_timer,
                         "Redrawing", /* parent */
                         "Painting actors",
@@ -522,11 +524,21 @@ _clutter_stage_glx_redraw (ClutterStageGLX *stage_glx,
 
   CLUTTER_TIMER_START (_clutter_uprof_context, painting_timer);
 
-  if (backend_glx->can_blit_sub_buffer &&
+  if (G_LIKELY (backend_glx->can_blit_sub_buffer) &&
       /* NB: a degenerate redraw clip width == full stage redraw */
-      (stage_glx->bounding_redraw_clip.width != 0) &&
+      stage_glx->bounding_redraw_clip.width != 0)
+    may_use_clipped_redraw = TRUE;
+  else
+    may_use_clipped_redraw = FALSE;
+
+  if (may_use_clipped_redraw &&
       G_LIKELY (!(clutter_paint_debug_flags &
                   CLUTTER_DEBUG_DISABLE_CLIPPED_REDRAWS)))
+    use_clipped_redraw = TRUE;
+  else
+    use_clipped_redraw = FALSE;
+
+  if (use_clipped_redraw)
     {
       cogl_clip_push_window_rectangle (stage_glx->bounding_redraw_clip.x,
                                        stage_glx->bounding_redraw_clip.y,
@@ -538,6 +550,52 @@ _clutter_stage_glx_redraw (ClutterStageGLX *stage_glx,
   else
     _clutter_stage_do_paint (stage);
 
+  if (clutter_paint_debug_flags & CLUTTER_DEBUG_REDRAWS &&
+      may_use_clipped_redraw)
+    {
+      ClutterGeometry *clip = &stage_glx->bounding_redraw_clip;
+      static CoglMaterial *outline = NULL;
+      CoglHandle vbo;
+      float x_1 = clip->x;
+      float x_2 = clip->x + clip->width;
+      float y_1 = clip->y;
+      float y_2 = clip->y + clip->height;
+      float quad[8] = {
+        x_1, y_1,
+        x_2, y_1,
+        x_2, y_2,
+        x_1, y_2
+      };
+      CoglMatrix modelview;
+
+      if (outline == NULL)
+        {
+          outline = cogl_material_new ();
+          cogl_material_set_color4ub (outline, 0xff, 0x00, 0x00, 0xff);
+        }
+
+      vbo = cogl_vertex_buffer_new (4);
+      cogl_vertex_buffer_add (vbo,
+                              "gl_Vertex",
+                              2, /* n_components */
+                              COGL_ATTRIBUTE_TYPE_FLOAT,
+                              FALSE, /* normalized */
+                              0, /* stride */
+                              quad);
+      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_LINE_LOOP,
+                               0 , 4);
+      cogl_pop_matrix ();
+      cogl_object_unref (vbo);
+    }
+
   cogl_flush ();
   CLUTTER_TIMER_STOP (_clutter_uprof_context, painting_timer);
 
@@ -558,11 +616,7 @@ _clutter_stage_glx_redraw (ClutterStageGLX *stage_glx,
     backend_glx->get_video_sync (&video_sync_count);
 
   /* push on the screen */
-  if (backend_glx->can_blit_sub_buffer &&
+  if (use_clipped_redraw)
-      /* NB: a degenerate redraw clip width == full stage redraw */
-      (stage_glx->bounding_redraw_clip.width != 0) &&
-      G_LIKELY (!(clutter_paint_debug_flags &
-                  CLUTTER_DEBUG_DISABLE_CLIPPED_REDRAWS)))
     {
       ClutterGeometry *clip = &stage_glx->bounding_redraw_clip;
       ClutterGeometry copy_area;
@@ -577,43 +631,6 @@ _clutter_stage_glx_redraw (ClutterStageGLX *stage_glx,
                     stage_glx->bounding_redraw_clip.width,
                     stage_glx->bounding_redraw_clip.height);
 
-      if (clutter_paint_debug_flags & CLUTTER_DEBUG_REDRAWS)
-        {
-          static CoglHandle outline = COGL_INVALID_HANDLE;
-          CoglHandle vbo;
-          float x_1 = clip->x;
-          float x_2 = clip->x + clip->width;
-          float y_1 = clip->y;
-          float y_2 = clip->y + clip->height;
-          float quad[8] = {
-            x_1, y_1,
-            x_2, y_1,
-            x_2, y_2,
-            x_1, y_2
-          };
-
-          if (outline == COGL_INVALID_HANDLE)
-            {
-              outline = cogl_material_new ();
-              cogl_material_set_color4ub (outline, 0xff, 0x00, 0x00, 0xff);
-            }
-
-          vbo = cogl_vertex_buffer_new (4);
-          cogl_vertex_buffer_add (vbo,
-                                  "gl_Vertex",
-                                  2, /* n_components */
-                                  COGL_ATTRIBUTE_TYPE_FLOAT,
-                                  FALSE, /* normalized */
-                                  0, /* stride */
-                                  quad);
-          cogl_vertex_buffer_submit (vbo);
-
-          cogl_set_source (outline);
-          cogl_vertex_buffer_draw (vbo, COGL_VERTICES_MODE_LINE_LOOP,
-                                   0 , 4);
-          cogl_flush ();
-        }
-
       /* XXX: It seems there will be a race here in that the stage
        * window may be resized before glXCopySubBufferMESA is handled
        * and so we may copy the wrong region. I can't really see how