WaylandBackend: avoid reattaching static black buffer

[connormclaud]

Keep the immutable 1x1 backing buffer attached across presents.

The Wayland core protocol says: "wl_surface.commit makes the pending wl_buffer the new surface contents." Reattaching the unchanged buffer on every paint is unnecessary.

fixes: #1636

[matte-schwartz]

I think the fix is better placed in how we track the black buffer than in CWaylandPlane::Present.

We probably want something more like:

diff --git a/src/Backends/WaylandBackend.cpp b/src/Backends/WaylandBackend.cpp
index d53c2c4..b3a1221 100644
--- a/src/Backends/WaylandBackend.cpp
+++ b/src/Backends/WaylandBackend.cpp
@@ -980,6 +980,9 @@ namespace gamescope

         xdg_log.debugf( "buffer_release: %p", pBuffer );

+        if ( this == m_pBackend->GetBlackFb() )
+            return;
+
         OnCompositorRelease();
     }

@@ -1106,8 +1109,6 @@ namespace gamescope
                 uint32_t uCurrentPlane = 0;
                 if ( bNeedsBacking )
                 {
-                    m_pBackend->GetBlackFb()->OnCompositorAcquire();
-
                     CWaylandPlane *pPlane = &m_Planes[uCurrentPlane++];
                     pPlane->Present(
                         WaylandPlaneState

can you check if that works? that way we don't need the BufferAttachPolicy/BufferAttachResult plumbing or the last-attached-buffer tracking

[connormclaud]

I have tested your patch works with glxgears, vkcube, Diablo 2 Resurrected and Antichamber and updated PR with it

[matte-schwartz]

thanks!