wayland: map windows with correct geometry

Consider a simple client that doesn't use set_window_geometry,
committing after attaching a buffer to a window surface.

Window::geometry falls back to Window::bbox, but when
Shell::map_window called Window::geometry, Window::bbox hadn't been
set yet, because that only happened later in
<State as CompositorHandler>::commit, so the window would be mapped
with a size of (0, 0).

This resulted in server-side decorations not being drawn for such
clients until they were re-focused or resized.

The fix is to add an extra call to Window::on_commit() before mapping
it, so that its bbox is set correctly when Shell::map_window asks for
its geometry.

src/wayland/handlers/compositor.rs

@@ -184,6 +184,7 @@ impl CompositorHandler for State {
                         && with_renderer_surface_state(&surface, |state| state.buffer().is_some())
                     {
                         let output = seat.active_output();
+                        window.on_commit();
                         Shell::map_window(self, &window, &output);
                     } else {
                         return;