Render top layer under fullscreen surfaces when stationary

src/layout.rs

@@ -1768,6 +1768,16 @@ impl<W: LayoutElement> Monitor<W> {
             }
         }
     }
+
+    pub fn render_above_top_layer(&self) -> bool {
+        // Render above the top layer only if the view is stationary.
+        if self.workspace_switch.is_some() {
+            return false;
+        }
+
+        let ws = &self.workspaces[self.active_workspace_idx];
+        ws.render_above_top_layer()
+    }
 }
 
 impl Monitor<Window> {
@@ -2449,6 +2459,19 @@ impl<W: LayoutElement> Workspace<W> {
         let value = !col.is_fullscreen;
         self.set_fullscreen(window, value);
     }
+
+    pub fn render_above_top_layer(&self) -> bool {
+        // Render above the top layer if we're on a fullscreen window and the view is stationary.
+        if self.columns.is_empty() {
+            return false;
+        }
+
+        if self.view_offset_anim.is_some() {
+            return false;
+        }
+
+        self.columns[self.active_column_idx].is_fullscreen
+    }
 }
 
 impl Workspace<Window> {

src/niri.rs

@@ -993,9 +993,21 @@ impl Niri {
                 })
         };
 
-        let (surface, surface_pos_within_output) = layer_surface_under(Layer::Overlay)
-            .or_else(|| layer_surface_under(Layer::Top))
-            .or_else(window_under)
+        let mon = self.layout.monitor_for_output(output).unwrap();
+
+        let mut under = layer_surface_under(Layer::Overlay);
+
+        if mon.render_above_top_layer() {
+            under = under
+                .or_else(window_under)
+                .or_else(|| layer_surface_under(Layer::Top));
+        } else {
+            under = under
+                .or_else(|| layer_surface_under(Layer::Top))
+                .or_else(window_under);
+        }
+
+        let (surface, surface_pos_within_output) = under
             .or_else(|| layer_surface_under(Layer::Bottom))
             .or_else(|| layer_surface_under(Layer::Background))?;
 
@@ -1440,11 +1452,15 @@ impl Niri {
 
         // The upper layer-shell elements go next.
         extend_from_layer(&mut elements, Layer::Overlay);
-        // FIXME: hide top layer when a fullscreen surface is showing somehow.
-        extend_from_layer(&mut elements, Layer::Top);
 
-        // Then the regular monitor elements.
-        elements.extend(monitor_elements.into_iter().map(OutputRenderElements::from));
+        // Then the regular monitor elements and the top layer in varying order.
+        if mon.render_above_top_layer() {
+            elements.extend(monitor_elements.into_iter().map(OutputRenderElements::from));
+            extend_from_layer(&mut elements, Layer::Top);
+        } else {
+            extend_from_layer(&mut elements, Layer::Top);
+            elements.extend(monitor_elements.into_iter().map(OutputRenderElements::from));
+        }
 
         // Then the lower layer-shell elements.
         extend_from_layer(&mut elements, Layer::Bottom);