wayland/surface: Unconditionally set scanout destination rect

The cogl_scanout_get_dst_rect() fell back on the buffer dimensions as
the destination rectangle when nothing was explicitly set. This,
however, is not necessarily correct. For example, if a buffer is larger
the CRTC resolution, but the surface is scaled to exactly match the CRTC view,
the expected destination size should match the CRTC resolution, not the
buffer dimension, which would be the case if no explicit destination was
set.

In meta_wayland_try_aquire_scanout() we're in a good position to
determine the destination rect in the CRTC primary plane, since we have
all the prerequisits, i.e. that the surface effectively covers the whole
CRTC, the actor allocation box (the non-black border part), the scale
and transform of the view.

This tweaks the CoglScanout API a bit to make it explicit that the
dst_rect must be unconditionally provided, and removes the fallback to
the buffer dimension as the destination rectangle, which sometimes
resulted in a destination rectangle being larger than the primary plane
itself, resulting in clipping and incorrect scaling.

Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/3773
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4147>

cogl/cogl/cogl-scanout.c

@@ -48,7 +48,6 @@ struct _CoglScanout
 
   gboolean has_src_rect;
   graphene_rect_t src_rect;
-  gboolean has_dst_rect;
   MtkRectangle dst_rect;
 };
 
@@ -104,11 +103,16 @@ cogl_scanout_notify_failed (CoglScanout  *scanout,
 }
 
 CoglScanout *
-cogl_scanout_new (CoglScanoutBuffer *scanout_buffer)
+cogl_scanout_new (CoglScanoutBuffer  *scanout_buffer,
+                  const MtkRectangle *dst_rect)
 {
-  CoglScanout *scanout = g_object_new (COGL_TYPE_SCANOUT, NULL);
+  CoglScanout *scanout;
 
+  g_return_val_if_fail (dst_rect, NULL);
+
+  scanout = g_object_new (COGL_TYPE_SCANOUT, NULL);
   scanout->scanout_buffer = scanout_buffer;
+  scanout->dst_rect = *dst_rect;
 
   return scanout;
 }
@@ -141,28 +145,9 @@ cogl_scanout_set_src_rect (CoglScanout           *scanout,
 
 void
 cogl_scanout_get_dst_rect (CoglScanout  *scanout,
-                           MtkRectangle *rect)
+                           MtkRectangle *dst_rect)
 {
-  if (scanout->has_dst_rect)
+  *dst_rect = scanout->dst_rect;
-    {
-      *rect = scanout->dst_rect;
-      return;
-    }
-
-  rect->x = 0;
-  rect->y = 0;
-  rect->width = cogl_scanout_buffer_get_width (scanout->scanout_buffer);
-  rect->height = cogl_scanout_buffer_get_height (scanout->scanout_buffer);
-}
-
-void
-cogl_scanout_set_dst_rect (CoglScanout        *scanout,
-                           const MtkRectangle *rect)
-{
-  if (rect != NULL)
-    scanout->dst_rect = *rect;
-
-  scanout->has_dst_rect = rect != NULL;
 }
 
 static void

cogl/cogl/cogl-scanout.h

@@ -81,7 +81,8 @@ void cogl_scanout_notify_failed (CoglScanout  *scanout,
                                  CoglOnscreen *onscreen);
 
 COGL_EXPORT
-CoglScanout * cogl_scanout_new (CoglScanoutBuffer *scanout_buffer);
+CoglScanout * cogl_scanout_new (CoglScanoutBuffer  *scanout_buffer,
+                                const MtkRectangle *dst_rect);
 
 COGL_EXPORT
 void cogl_scanout_get_src_rect (CoglScanout     *scanout,
@@ -93,8 +94,4 @@ void cogl_scanout_set_src_rect (CoglScanout           *scanout,
 
 COGL_EXPORT
 void cogl_scanout_get_dst_rect (CoglScanout  *scanout,
-                                MtkRectangle *rect);
+                                MtkRectangle *dst_rect);
-
-COGL_EXPORT
-void cogl_scanout_set_dst_rect (CoglScanout        *scanout,
-                                const MtkRectangle *rect);

src/wayland/meta-wayland-buffer.c

@@ -924,9 +924,9 @@ try_acquire_egl_image_scanout (MetaWaylandBuffer     *buffer,
       return NULL;
     }
 
-  scanout = cogl_scanout_new (COGL_SCANOUT_BUFFER (g_steal_pointer (&fb)));
+  scanout = cogl_scanout_new (COGL_SCANOUT_BUFFER (g_steal_pointer (&fb)),
+                              dst_rect);
   cogl_scanout_set_src_rect (scanout, src_rect);
-  cogl_scanout_set_dst_rect (scanout, dst_rect);
   if (!meta_onscreen_native_is_buffer_scanout_compatible (onscreen, scanout))
     return NULL;
 

src/wayland/meta-wayland-dma-buf.c

@@ -666,9 +666,9 @@ meta_wayland_dma_buf_try_acquire_scanout (MetaWaylandBuffer     *buffer,
       return NULL;
     }
 
-  scanout = cogl_scanout_new (COGL_SCANOUT_BUFFER (g_steal_pointer (&fb)));
+  scanout = cogl_scanout_new (COGL_SCANOUT_BUFFER (g_steal_pointer (&fb)),
+                              dst_rect);
   cogl_scanout_set_src_rect (scanout, src_rect);
-  cogl_scanout_set_dst_rect (scanout, dst_rect);
 
   if (!meta_onscreen_native_is_buffer_scanout_compatible (onscreen, scanout))
     {

src/wayland/meta-wayland-surface.c

@@ -2409,7 +2409,6 @@ meta_wayland_surface_try_acquire_scanout (MetaWaylandSurface *surface,
   MetaSurfaceActor *surface_actor;
   MtkMonitorTransform view_transform;
   ClutterActorBox actor_box;
-  MtkRectangle *crtc_dst_rect_ptr = NULL;
   MtkRectangle crtc_dst_rect;
   graphene_rect_t *src_rect_ptr = NULL;
   graphene_rect_t src_rect;
@@ -2465,13 +2464,6 @@ meta_wayland_surface_try_acquire_scanout (MetaWaylandSurface *surface,
                            view_crtc_height,
                            &crtc_dst_rect);
 
-  /* Use an implicit destination rect when possible */
-  if (surface->viewport.has_dst_size ||
-      crtc_dst_rect.x != 0 || crtc_dst_rect.y != 0 ||
-      crtc_dst_rect.width != view_crtc_width ||
-      crtc_dst_rect.height != view_crtc_height)
-    crtc_dst_rect_ptr = &crtc_dst_rect;
-
   if (surface->viewport.has_src_rect)
     {
       src_rect = surface->viewport.src_rect;
@@ -2481,7 +2473,7 @@ meta_wayland_surface_try_acquire_scanout (MetaWaylandSurface *surface,
   return meta_wayland_buffer_try_acquire_scanout (surface->buffer,
                                                   onscreen,
                                                   src_rect_ptr,
-                                                  crtc_dst_rect_ptr);
+                                                  &crtc_dst_rect);
 }
 
 MetaCrtc *