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, 1 insertions, 0 deletions

diff --git a/crates/wayland/src/winit/connect.rs b/crates/wayland/src/winit/connect.rs
index 0f3a6d3..41e9b2a 100644
--- a/crates/wayland/src/winit/connect.rs
+++ b/crates/wayland/src/winit/connect.rs
@@ -152,6 +152,7 @@ impl WaylandPlatform {
             id_to_window: HashMap::new(),
             dead_layer_surfaces: HashSet::new(),
             hidden_layer_surfaces: HashMap::new(),
+            layer_surfaces_shown_once: HashSet::new(),
             decorations: HashMap::new(),
             border_top_decorations: HashMap::new(),
             border_bottom_decorations: HashMap::new(),