Fix layer surfaces spuriously hiding/re-showing on their own realization

sync_layer_visibility could not tell a real hide (null-buffer commit on
an already-visible surface) apart from a layer-shell client's ordinary
realization sequence (commit with no buffer -> configure -> ack-commit
with no buffer again -> attach real content): both look like "committed,
no buffer" from has_buffer alone. Every layer surface's first realization
was spuriously unmapped and immediately remapped, doubling LayerMap
arrange() passes on every single popup open.

Live-reproduced via an AGS peer session: a full-monitor click-outside-to-
close popup surface came back from a hit-test with geometry wider than
the real output after several open/close cycles on a wl_surface GTK had
reused across role destroy/recreate, and sat in the Top layer above every
real window with no input region set - silently swallowing clicks meant
for windows, dropdowns, and CSD title bars alike.

layer_surfaces_shown_once now gates the hide path on a surface having
actually shown a buffer at least once, and is cleared in layer_destroyed
so a reused wl_surface's next role starts clean rather than inheriting
the previous role's flag.

1 files changed, 9 insertions, 0 deletions

diff --git a/crates/wayland/src/protocols.rs b/crates/wayland/src/protocols.rs
index 94075c2..0b0eea2 100644
--- a/crates/wayland/src/protocols.rs
+++ b/crates/wayland/src/protocols.rs
@@ -661,6 +661,15 @@ impl WlrLayerShellHandler for CompState {
         // `new_surface` - see that function's doc comment for the bug
         // this exists to route around.
         self.dead_layer_surfaces.insert(surface.wl_surface().clone());
+        // GTK (confirmed live via an AGS peer session's WAYLAND_DEBUG trace)
+        // reuses the same `wl_surface` for the next `get_layer_surface` role
+        // rather than creating a fresh one - so without this, a "shown at
+        // least once" flag from *this* role would leak onto the next one
+        // and make `sync_layer_visibility` treat that new role's own
+        // ack-configure commit as eligible to hide again, the same bug
+        // `layer_surfaces_shown_once` exists to prevent, just reintroduced
+        // for exactly the reused-surface case that matters here.
+        self.layer_surfaces_shown_once.remove(surface.wl_surface());
         // The surface belongs to exactly one output's map, but which one is
         // the client's choice, so unmap from whichever holds it.
         for output in self.outputs().cloned().collect::<Vec<_>>() {