fix: keep windows visible until overview commits a buffer

src/utils/quirks.rs

@@ -1,6 +1,9 @@
 // SPDX-License-Identifier: GPL-3.0-only
 
-use smithay::{desktop::layer_map_for_output, output::Output};
+use smithay::{
+    backend::renderer::utils::with_renderer_surface_state, desktop::layer_map_for_output,
+    output::Output,
+};
 
 /// Layer shell namespace used by `cosmic-workspaces`
 // TODO: Avoid special case, or add protocol to expose required behavior
@@ -10,5 +13,14 @@ pub const WORKSPACE_OVERVIEW_NAMESPACE: &str = "cosmic-workspace-overview";
 pub fn workspace_overview_is_open(output: &Output) -> bool {
     layer_map_for_output(output)
         .layers()
-        .any(|s| s.namespace() == WORKSPACE_OVERVIEW_NAMESPACE)
+        .filter(|s| s.namespace() == WORKSPACE_OVERVIEW_NAMESPACE)
+        // Only consider the overview open once it has committed a buffer. The
+        // surface is inserted into the layer map on its initial (bufferless)
+        // commit, so checking for the namespace alone hides all toplevels for a
+        // frame before the overview has anything to draw, briefly flashing the
+        // bare wallpaper.
+        .any(|s| {
+            with_renderer_surface_state(s.wl_surface(), |state| state.buffer().is_some())
+                .unwrap_or(false)
+        })
 }