window: Don't check always-on-top overlap before placing

When we show a window, we'll check if it overlaps with an existing
always-on-top window with the intention to deny focus. However, we did
this potentially before having placed the window, meaning we effectively
checked as if it was placed at (0, 0), which created unexpected results.

Instead check the overlap state after placing. A window placement test
case is added to verify this works as expected.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3879>

src/core/place.c

@@ -353,7 +353,9 @@ find_most_freespace (MetaWindow *window,
 }
 
 static gboolean
-window_overlaps_focus_window (MetaWindow *window)
+window_overlaps_focus_window (MetaWindow *window,
+                              int         new_x,
+                              int         new_y)
 {
   MetaWindow *focus_window;
   MtkRectangle window_frame, focus_frame, overlap;
@@ -363,6 +365,9 @@ window_overlaps_focus_window (MetaWindow *window)
     return FALSE;
 
   meta_window_get_frame_rect (window, &window_frame);
+  window_frame.x = new_x;
+  window_frame.y = new_y;
+
   meta_window_get_frame_rect (focus_window, &focus_frame);
 
   return mtk_rectangle_intersect (&window_frame,
@@ -414,7 +419,7 @@ avoid_being_obscured_as_second_modal_dialog (MetaWindow    *window,
 #ifdef HAVE_X11_CLIENT
       meta_window_x11_same_application (window, focus_window) &&
 #endif
-      window_overlaps_focus_window (window))
+      window_overlaps_focus_window (window, *x, *y))
     {
       find_most_freespace (window, focus_window, *x, *y, x, y);
       meta_topic (META_DEBUG_PLACEMENT,
@@ -987,7 +992,7 @@ meta_window_place (MetaWindow        *window,
       g_assert (focus_window != NULL);
 
       /* No need to do anything if the window doesn't overlap at all */
-      found_fit = !window_overlaps_focus_window (window);
+      found_fit = !window_overlaps_focus_window (window, x, y);
 
       /* Try to do a first fit again, this time only taking into account the
        * focus window.

src/core/window.c

@@ -2284,8 +2284,8 @@ meta_window_show (MetaWindow *window)
   if (focus_window &&
       window->showing_for_first_time &&
       !meta_window_is_ancestor_of_transient (focus_window, window) &&
-      ((!place_on_top_on_map && !takes_focus_on_map) ||
+      !place_on_top_on_map &&
-       window_would_be_covered_by_always_above_window (window)))
+      !takes_focus_on_map)
     {
       needs_stacking_adjustment = TRUE;
       if (!window->placed)
@@ -2316,6 +2316,12 @@ meta_window_show (MetaWindow *window)
       meta_window_force_placement (window, place_flags);
     }
 
+  if (focus_window &&
+      window->showing_for_first_time &&
+      !meta_window_is_ancestor_of_transient (focus_window, window) &&
+      window_would_be_covered_by_always_above_window (window))
+    needs_stacking_adjustment = TRUE;
+
   if (needs_stacking_adjustment)
     {
       gboolean overlap;

src/tests/meson.build

@@ -726,6 +726,7 @@ stacking_tests = [
   'workspace-basic',
   'workspace-test',
   'always-on-top',
+  'always-on-top-map-new-maximized',
   'focus-default-window-globally-active-input',
   'workspace-unmanaging-window',
   'click-to-focus-and-raise',
@@ -739,7 +740,8 @@ stacking_tests = [
   'sticky',
   'sticky-modals',
   'sticky-transients',
-  'strut-monitor-changes'
+  'strut-monitor-changes',
+  'window-placement',
 ]
 
 foreach stacking_test: stacking_tests

src/tests/stacking/always-on-top-map-new-maximized.metatest

@@ -0,0 +1,20 @@
+resize_monitor default 400 400
+
+new_client w wayland
+create w/1 csd
+resize w/1 350 350
+show w/1
+move w/1 25 25
+make_above w/1 true
+
+assert_focused w/1
+assert_stacking w/1
+
+# Map a maximized window; it should not gain focus due to being mostly covered.
+
+create w/2 csd
+maximize w/2
+show w/2
+
+assert_focused w/1
+assert_stacking w/2 w/1

src/tests/stacking/window-placement.metatest

@@ -0,0 +1,84 @@
+new_client w wayland
+resize_monitor default 250 250
+set_pref center-new-windows false
+
+# Show 4 windows in a row and assert that they are placed in a grid and focused
+# correctly.
+
+create w/1 csd
+resize w/1 100 100
+show w/1
+
+assert_focused w/1
+assert_position w/1 24 16
+assert_size w/1 100 100
+
+create w/2 csd
+resize w/2 100 100
+show w/2
+
+assert_focused w/2
+assert_position w/2 24 116
+assert_size w/2 100 100
+
+create w/3 csd
+resize w/3 100 100
+show w/3
+
+assert_focused w/3
+assert_position w/3 124 16
+assert_size w/3 100 100
+
+create w/4 csd
+resize w/4 100 100
+show w/4
+
+assert_focused w/4
+assert_position w/4 124 116
+assert_size w/4 100 100
+
+destroy w/1
+destroy w/2
+destroy w/3
+destroy w/4
+wait
+
+assert_stacking
+
+
+# Show 1 window, make it 'always-on-top' and make sure the following windows
+# still get placed and focused correctly.
+
+create w/1 csd
+resize w/1 100 100
+show w/1
+
+assert_focused w/1
+assert_position w/1 24 16
+assert_size w/1 100 100
+
+make_above w/1 true
+
+create w/2 csd
+resize w/2 100 100
+show w/2
+
+assert_focused w/2
+assert_position w/2 24 116
+assert_size w/2 100 100
+
+create w/3 csd
+resize w/3 100 100
+show w/3
+
+assert_focused w/3
+assert_position w/3 124 16
+assert_size w/3 100 100
+
+create w/4 csd
+resize w/4 100 100
+show w/4
+
+assert_focused w/4
+assert_position w/4 124 116
+assert_size w/4 100 100