Add workspace_overview_is_open function; put in a utils::quirks mod

This is increasingly not just related to screencopy, so it's weird to
add there. I don't see any other module that fits, so add one called
"quirks" (like the Linux kernel uses for device-specific handling in
generic drives).

src/utils/mod.rs

@@ -5,6 +5,7 @@ pub(crate) use self::ids::id_gen;
 pub mod geometry;
 pub mod iced;
 pub mod prelude;
+pub mod quirks;
 pub mod rlimit;
 pub mod screenshot;
 pub mod tween;

src/utils/quirks.rs

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-3.0-only
+
+use smithay::{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
+pub const WORKSPACE_OVERVIEW_NAMESPACE: &str = "cosmic-workspace-overview";
+
+/// Check if a workspace overview shell surface is open on the output
+pub fn workspace_overview_is_open(output: &Output) -> bool {
+    layer_map_for_output(output)
+        .layers()
+        .any(|s| s.namespace() == WORKSPACE_OVERVIEW_NAMESPACE)
+}