Detect XWayland dialogs via WM_TRANSIENT_FOR, not just native xdg_toplevel parent

Window::is_dialog (close-button-only titlebar, no traffic lights) was
only ever set from a native xdg_toplevel's own parent() - redraw_
decoration_buffer's is_dialog computation called dw.toplevel(), which
is always None for an XWayland-backed DWindow (X11Surface's own
accessor is x11_surface(), a different method), so the .unwrap_or(false)
fallback made every XWayland dialog - a GTK "Save As", an app's own
"About" box, anything setting the ICCCM transient-for hint - always
draw with the full three-button titlebar and traffic-light colours,
even though the feature this was built for explicitly wanted the
opposite. Documented as a known gap at the time; now closed.

redraw_decoration_buffer now also checks X11Surface::is_transient_for()
for an XWayland window. property_notify gained a WmWindowProperty::
TransientFor arm that re-runs redraw_decoration_buffer, for a client
that sets the hint slightly after its own initial map - the same
"read fresh every call" pattern the existing xdg_toplevel::parent()
check already relied on, extended to catch a late X11 property the way
the Wayland equivalent (set_parent, any time) already was.

1 files changed, 15 insertions, 0 deletions

diff --git a/crates/wayland/src/xwayland.rs b/crates/wayland/src/xwayland.rs
index a51ee97..7834f16 100644
--- a/crates/wayland/src/xwayland.rs
+++ b/crates/wayland/src/xwayland.rs
@@ -825,6 +825,21 @@ impl XwmHandler for CompState {
     /// (a dock's running-indicator, an app switcher, icon lookup), not just
     /// this compositor's own UI.
     fn property_notify(&mut self, _xwm: XwmId, window: X11Surface, property: WmWindowProperty) {
+        // `WM_TRANSIENT_FOR` - `Window::is_dialog`'s own X11 half (see its
+        // doc comment) - can arrive after the window's already mapped and
+        // decorated: a client that sets it slightly late, or one this
+        // compositor granted the map request for before XWayland finished
+        // resolving the property. `redraw_decoration_buffer` re-reads
+        // `is_transient_for()` fresh every call, so simply calling it again
+        // here picks up the change - same "cheap once nothing's actually
+        // different" self-guard (`decoration_signatures`) every other
+        // redraw trigger in this codebase already relies on.
+        if matches!(property, WmWindowProperty::TransientFor) {
+            if let Some(&id) = self.xwayland_windows.get(&window.window_id()) {
+                self.redraw_decoration_buffer(id);
+            }
+            return;
+        }
         if !matches!(property, WmWindowProperty::Title | WmWindowProperty::Class) {
             return;
         }