shaped-texture: Fix use-nearest check when viewports are scaled

We checked that the content size was appropriately painted in the stage,
but didn't take into account that the size of the sampled texture
region, meaning that when stage views were scaled, we'd think that we
would draw a texture scaled, as e.g. a 200x200 sized texture with buffer
scale 2 would have the size 100x100. When stage views were not scaled,
we'd apply a geometry scale meaning it'd end up as 200x200 anyway, thus
pass the check, but when stage views are scaled, it'd still be painted
as a 100x100 shaped texture on the stage, thus failing the
are-we-unscaled test.

Fix this by comparing the transformed paint size with the sampled size,
instead of the paint size again, when checking whether we are being
painted scaled or not. For example, when stage views are scaled, our
200x200 buffer with buffer scale 2, thus content size 100x100 will
transform to a 200x200 paint command, thus passing the test. For
non-scaled stage views, our 200x200 buffer with buffer scale 2 thus
content size 100x100 will also transform into a 200x200 paint command,
and will also pass the check, as the texture sample region is still
200x200.

Fixes: https://gitlab.gnome.org/GNOME/mutter/issues/804

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1124

src/compositor/clutter-utils.c

@@ -115,6 +115,8 @@ meta_actor_vertices_are_untransformed (graphene_point3d_t *verts,
  * meta_actor_painting_untransformed:
  * @paint_width: the width of the painted area
  * @paint_height: the height of the painted area
+ * @sample_width: the width of the sampled area of the texture
+ * @sample_height: the height of the sampled area of the texture
  * @x_origin: if the transform is only an integer translation
  *  then the X coordinate of the location of the origin under the transformation
  *  from drawing space to screen pixel space is returned here.
@@ -133,6 +135,8 @@ gboolean
 meta_actor_painting_untransformed (CoglFramebuffer *fb,
                                    int              paint_width,
                                    int              paint_height,
+                                   int              sample_width,
+                                   int              sample_height,
                                    int             *x_origin,
                                    int             *y_origin)
 {
@@ -177,6 +181,8 @@ meta_actor_painting_untransformed (CoglFramebuffer *fb,
                                       viewport[3], viewport[1]);
     }
 
-  return meta_actor_vertices_are_untransformed (vertices, paint_width, paint_height, x_origin, y_origin);
+  return meta_actor_vertices_are_untransformed (vertices,
+                                                sample_width, sample_height,
+                                                x_origin, y_origin);
 }
 

src/compositor/clutter-utils.h

@@ -32,6 +32,8 @@ gboolean meta_actor_vertices_are_untransformed (graphene_point3d_t *verts,
 gboolean meta_actor_painting_untransformed (CoglFramebuffer *fb,
                                             int              paint_width,
                                             int              paint_height,
+                                            int              sample_widthf,
+                                            int              sample_heightf,
                                             int             *x_origin,
                                             int             *y_origin);
 

src/compositor/meta-background-actor.c

@@ -450,6 +450,8 @@ setup_pipeline (MetaBackgroundActor   *self,
   fb = clutter_paint_context_get_framebuffer (paint_context);
   if (!self->force_bilinear &&
       meta_actor_painting_untransformed (fb,
+                                         actor_pixel_rect->width,
+                                         actor_pixel_rect->height,
                                          actor_pixel_rect->width,
                                          actor_pixel_rect->height,
                                          NULL, NULL))

src/compositor/meta-shaped-texture.c

@@ -507,6 +507,17 @@ texture_is_idle_and_not_mipmapped (gpointer user_data)
   return G_SOURCE_REMOVE;
 }
 
+static inline void
+flip_ints (int *x,
+           int *y)
+{
+  int tmp;
+
+  tmp = *x;
+  *x = *y;
+  *y = tmp;
+}
+
 static void
 do_paint_content (MetaShapedTexture   *stex,
                   ClutterPaintNode    *root_node,
@@ -522,6 +533,7 @@ do_paint_content (MetaShapedTexture   *stex,
   CoglContext *ctx;
   CoglPipelineFilter filter;
   CoglFramebuffer *framebuffer;
+  int sample_width, sample_height;
 
   ensure_size_valid (stex);
 
@@ -542,15 +554,30 @@ do_paint_content (MetaShapedTexture   *stex,
    * improves performance, especially with software rendering.
    */
 
-  filter = COGL_PIPELINE_FILTER_LINEAR;
-
   framebuffer = clutter_paint_node_get_framebuffer (root_node);
   if (!framebuffer)
     framebuffer = clutter_paint_context_get_framebuffer (paint_context);
+
+  if (stex->has_viewport_src_rect)
+    {
+      sample_width = stex->viewport_src_rect.size.width * stex->buffer_scale;
+      sample_height = stex->viewport_src_rect.size.height * stex->buffer_scale;
+    }
+  else
+    {
+      sample_width = cogl_texture_get_width (stex->texture);
+      sample_height = cogl_texture_get_height (stex->texture);
+    }
+  if (meta_monitor_transform_is_rotated (stex->transform))
+    flip_ints (&sample_width, &sample_height);
+
   if (meta_actor_painting_untransformed (framebuffer,
                                          dst_width, dst_height,
+                                         sample_width, sample_height,
                                          NULL, NULL))
     filter = COGL_PIPELINE_FILTER_NEAREST;
+  else
+    filter = COGL_PIPELINE_FILTER_LINEAR;
 
   ctx = clutter_backend_get_cogl_context (clutter_get_default_backend ());
 

src/compositor/meta-window-group.c

@@ -94,6 +94,8 @@ meta_window_group_paint (ClutterActor        *actor,
 
       fb = clutter_paint_context_get_framebuffer (paint_context);
       if (!meta_actor_painting_untransformed (fb,
+                                              screen_width,
+                                              screen_height,
                                               screen_width,
                                               screen_height,
                                               &paint_x_origin,