[five-or-more/arnaudb/wip/gtk4: 59/80] Make on_window_state_event work.

[Arnaud B. <arnaudb src gnome org>]

commit 3ed1794b25beeb8e9bffd283880590f97010b0ab
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Thu Mar 12 23:20:06 2020 +0100

    Make on_window_state_event work.

 src/window.vala | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)
---
diff --git a/src/window.vala b/src/window.vala
index 9f6e048..276d1e1 100644
--- a/src/window.vala
+++ b/src/window.vala
@@ -74,6 +74,8 @@ private class GameWindow : ApplicationWindow
     {
         add_action_entries (win_actions, this);
 
+        map.connect (init_state_watcher);
+
         SimpleAction theme_action = (SimpleAction) lookup_action ("change-theme");
         string theme_value = settings.get_string (FiveOrMoreApp.KEY_THEME);
         if (theme_value != "balls.svg" && theme_value != "shapes.svg" && theme_value != "tango.svg") /* TODO 
use an enum in GSchema file? */
@@ -125,15 +127,27 @@ private class GameWindow : ApplicationWindow
         init_scores_dialog ();
     }
 
-    protected override bool window_state_event (Gdk.EventWindowState event)
+    private void init_state_watcher ()
     {
-        if ((event.changed_mask & Gdk.WindowState.MAXIMIZED) != 0)
-            window_maximized = (event.new_window_state & Gdk.WindowState.MAXIMIZED) != 0;
+        Gdk.Surface? nullable_surface = get_surface ();     // TODO report bug, get_surface() returns a 
nullable Surface
+        if (nullable_surface == null || !((!) nullable_surface is Gdk.Toplevel))
+            assert_not_reached ();
+        surface = (Gdk.Toplevel) (!) nullable_surface;
+        surface.notify ["state"].connect (on_window_state_event);
+    }
 
-        if ((event.changed_mask & Gdk.WindowState.TILED) != 0)
-            window_tiled = (event.new_window_state & Gdk.WindowState.TILED) != 0;
+    private Gdk.Toplevel surface;
+    private const Gdk.ToplevelState tiled_state = Gdk.ToplevelState.TILED
+                                                | Gdk.ToplevelState.TOP_TILED
+                                                | Gdk.ToplevelState.BOTTOM_TILED
+                                                | Gdk.ToplevelState.LEFT_TILED
+                                                | Gdk.ToplevelState.RIGHT_TILED;
+    private inline void on_window_state_event ()
+    {
+        Gdk.ToplevelState state = surface.get_state ();
 
-        return false;
+        window_maximized =  (state & Gdk.ToplevelState.MAXIMIZED) != 0;
+        window_tiled =      (state & tiled_state)                 != 0;
     }
 
     protected override void size_allocate (Allocation allocation)