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.

2 files changed, 33 insertions, 5 deletions

diff --git a/crates/wayland/src/state/lifecycle.rs b/crates/wayland/src/state/lifecycle.rs
index b47cb23..53a5e86 100644
--- a/crates/wayland/src/state/lifecycle.rs
+++ b/crates/wayland/src/state/lifecycle.rs
@@ -81,11 +81,24 @@ impl CompState {
         // change. Written back onto the real `Window` (not just used
         // locally) so `ResizeEdge::hit_test`'s own `is_dialog` parameter
         // - read from `core`, which has no protocol concept to derive
-        // this from itself - agrees with whatever got drawn here. An
-        // XWayland window's own `WM_TRANSIENT_FOR` isn't read yet, so this
-        // stays `false` for those specifically - see `Window::is_dialog`'s
-        // own doc comment.
-        let is_dialog = self.id_to_window.get(&id).and_then(|dw| dw.toplevel()).map(|t| t.parent().is_some()).unwrap_or(false);
+        // this from itself - agrees with whatever got drawn here.
+        //
+        // Checks both real toplevel kinds a `DWindow` can wrap: a native
+        // `xdg_toplevel`'s own `parent()`, or an XWayland `X11Surface`'s
+        // `WM_TRANSIENT_FOR` via `is_transient_for()`. The X11 half used
+        // to be unchecked entirely (`.toplevel()` alone, which is always
+        // `None` for an X11-backed window - `X11Surface`'s own accessor
+        // is `.x11_surface()`, a different method), so every XWayland
+        // dialog - a GTK "Save As", an app's own "About" box, anything
+        // that sets the ICCCM transient-for hint - always drew with the
+        // full three-button titlebar and traffic-light colours, the
+        // native-Wayland-only case this whole feature was built for.
+        // Reported live: "dialog windows... should never have traffic
+        // light, should just be x" - true for native Wayland dialogs
+        // already, not for XWayland ones.
+        let is_dialog = self.id_to_window.get(&id).is_some_and(|dw| {
+            dw.toplevel().is_some_and(|t| t.parent().is_some()) || dw.x11_surface().is_some_and(|x| x.is_transient_for().is_some())
+        });
         if let Some(win) = self.wm.borrow_mut().window_mut(id) {
             win.is_dialog = is_dialog;
         }
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;
         }