offload: Fix handling of clips

When we are inside a non-representable clip, we can't offload. The
reason for this is that the renderer will offscreen due to that
clip, and then the hole we need to punch will end up in the offscreen
and not in the main surface where we need it.

Fixes: #6499

gsk/gskoffload.c

@@ -38,7 +38,7 @@ typedef struct
   guint is_rectilinear     : 1;
   guint is_fully_contained : 1;
   guint is_empty           : 1;
-  guint is_complex         : 1;
+  guint is_complex         : 1; /* Inside a non-representable clip, even if fully contained */
 } Clip;
 
 struct _GskOffload
@@ -225,10 +225,13 @@ static void
 push_rect_clip (GskOffload           *self,
                 const GskRoundedRect *rect)
 {
+  Clip *current_clip = self->clips->data;
   Clip *clip = g_new0 (Clip, 1);
+
   clip->rect = *rect;
   clip->is_rectilinear = gsk_rounded_rect_is_rectilinear (rect);
   clip->is_empty = (rect->bounds.size.width == 0 || rect->bounds.size.height == 0);
+  clip->is_complex = current_clip && current_clip->is_complex;
 
   self->clips = g_slist_prepend (self->clips, clip);
   self->current_clip = self->clips->data;
@@ -249,6 +252,7 @@ push_contained_clip (GskOffload *self)
   clip->rect = current_clip->rect;
   clip->is_rectilinear = TRUE;
   clip->is_fully_contained = TRUE;
+  clip->is_complex = current_clip && current_clip->is_complex;
 
   self->clips = g_slist_prepend (self->clips, clip);
   self->current_clip = self->clips->data;
@@ -278,6 +282,8 @@ pop_clip (GskOffload *self)
   self->clips = self->clips->next;
   if (self->clips)
     self->current_clip = self->clips->data;
+  else
+    self->current_clip = NULL;
 
   g_slist_free_1 (l);
   g_free (clip);
@@ -454,7 +460,7 @@ visit_node (GskOffload    *self,
     case GSK_MASK_NODE:
     case GSK_FILL_NODE:
     case GSK_STROKE_NODE:
-    break;
+      break;
 
     case GSK_CLIP_NODE:
       {
@@ -515,21 +521,21 @@ visit_node (GskOffload    *self,
               push_empty_clip (self);
             else if (result == GSK_INTERSECTION_NONEMPTY)
               push_rect_clip (self, &intersection);
+            else if (gsk_rounded_rect_contains_rect (&self->current_clip->rect, &transformed_clip.bounds))
+              push_rect_clip (self, &transformed_clip);
             else
-              goto complex_clip;
-            visit_node (self, gsk_rounded_clip_node_get_child (node));
-            pop_clip (self);
+              push_complex_clip (self);
           }
         else
           {
-complex_clip:
             if (gsk_rounded_rect_contains_rect (&self->current_clip->rect, &transformed_clip.bounds))
               push_rect_clip (self, &transformed_clip);
             else
               push_complex_clip (self);
-            visit_node (self, gsk_rounded_clip_node_get_child (node));
-            pop_clip (self);
           }
+
+        visit_node (self, gsk_rounded_clip_node_get_child (node));
+        pop_clip (self);
       }
       break;
 
@@ -566,6 +572,12 @@ complex_clip:
                                "Can't offload subsurface %p: clipped",
                                subsurface);
           }
+        else if (self->current_clip->is_complex)
+          {
+            GDK_DISPLAY_DEBUG (gdk_surface_get_display (self->surface), OFFLOAD,
+                               "Can't offload subsurface %p: inside non-representable clip",
+                               subsurface);
+          }
         else if (self->transforms &&
                  gsk_transform_get_category ((GskTransform *)self->transforms->data) < GSK_TRANSFORM_CATEGORY_2D_AFFINE)
           {
@@ -594,7 +606,7 @@ complex_clip:
     case GSK_NOT_A_RENDER_NODE:
     default:
       g_assert_not_reached ();
-    break;
+      break;
     }
 
   if (has_clip)