[mutter] clutter/stage-cogl: Check for DISABLE_CLIPPED_REDRAWS earlier

[Jonas Ådahl <jadahl src gnome org>]

commit 08f47fee165945dcc83322b1a408bd86d73ed965
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Fri Mar 6 12:15:55 2020 +0100

    clutter/stage-cogl: Check for DISABLE_CLIPPED_REDRAWS earlier
    
    Right now we're checking for the DISABLE_CLIPPED_REDRAWS debug flag
    after creating the fb_clip_region and adjusting the redraw_clip. That
    means that if may_use_clipped_redraw was TRUE, the redraw_clip will
    still be set to the region and thus cause the stage to only be partially
    redrawn. Since we don't push a clip to the framebuffer though
    (use_clipped_redraw is now FALSE), parts of the view will get corrupted.
    
    To fix that, disable clipped redraws right away if the debug flag is
    set. This also allows removing the may_use_clipped_redraw bool and
    replacing it entirely with use_clipped_redraw.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1113

 clutter/clutter/cogl/clutter-stage-cogl.c | 36 +++++++++++++++----------------
 1 file changed, 17 insertions(+), 19 deletions(-)
---
diff --git a/clutter/clutter/cogl/clutter-stage-cogl.c b/clutter/clutter/cogl/clutter-stage-cogl.c
index fdae815e2..be37f3487 100644
--- a/clutter/clutter/cogl/clutter-stage-cogl.c
+++ b/clutter/clutter/cogl/clutter-stage-cogl.c
@@ -575,7 +575,6 @@ clutter_stage_cogl_redraw_view (ClutterStageWindow *stage_window,
   CoglFramebuffer *fb = clutter_stage_view_get_framebuffer (view);
   cairo_rectangle_int_t view_rect;
   gboolean is_full_redraw;
-  gboolean may_use_clipped_redraw;
   gboolean use_clipped_redraw;
   gboolean can_blit_sub_buffer;
   gboolean has_buffer_age;
@@ -611,25 +610,29 @@ clutter_stage_cogl_redraw_view (ClutterStageWindow *stage_window,
   else
     is_full_redraw = FALSE;
 
-  may_use_clipped_redraw =
-    _clutter_stage_window_can_clip_redraws (stage_window) &&
-    (can_blit_sub_buffer || has_buffer_age) &&
-    !is_full_redraw &&
-    /* some drivers struggle to get going and produce some junk
-     * frames when starting up... */
-    cogl_onscreen_get_frame_counter (COGL_ONSCREEN (fb)) > 3;
-
   if (has_buffer_age)
     {
       buffer_age = cogl_onscreen_get_buffer_age (COGL_ONSCREEN (fb));
       if (!valid_buffer_age (view_cogl, buffer_age))
         {
-          CLUTTER_NOTE (CLIPPING, "Invalid back buffer(age=%d): forcing full redraw\n", buffer_age);
-          may_use_clipped_redraw = FALSE;
+          CLUTTER_NOTE (CLIPPING,
+                        "Invalid back buffer(age=%d): forcing full redraw\n",
+                        buffer_age);
+          use_clipped_redraw = FALSE;
         }
     }
 
-  if (may_use_clipped_redraw)
+  use_clipped_redraw =
+    use_clipped_redraw &&
+    !(clutter_paint_debug_flags & CLUTTER_DEBUG_DISABLE_CLIPPED_REDRAWS) &&
+    _clutter_stage_window_can_clip_redraws (stage_window) &&
+    (can_blit_sub_buffer || has_buffer_age) &&
+    !is_full_redraw &&
+    /* some drivers struggle to get going and produce some junk
+     * frames when starting up... */
+    cogl_onscreen_get_frame_counter (COGL_ONSCREEN (fb)) > 3;
+
+  if (use_clipped_redraw)
     {
       fb_clip_region = offset_scale_and_clamp_region (redraw_clip,
                                                       -view_rect.x,
@@ -650,13 +653,8 @@ clutter_stage_cogl_redraw_view (ClutterStageWindow *stage_window,
       redraw_clip = cairo_region_create_rectangle (&view_rect);
     }
 
-  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;
-
-  clip_region_empty = may_use_clipped_redraw && cairo_region_is_empty (fb_clip_region);
+  clip_region_empty = (use_clipped_redraw &&
+                       cairo_region_is_empty (fb_clip_region));
 
   swap_with_damage = FALSE;
   if (has_buffer_age)