Merge ea01d1963c into 6d89a6bc15

Prior to this fix, if all of the following conditions were met:
+ While a modal window (such as the Preferences dialog) was open.
+ 'Multiple window UI' was enabled.
+ A non-modal window (such as the Preview window) overlapped the modal
  window.
+ The non-modal window was selected, so this window is on top of
  the modal window.
Caused mouse clicks and movements within the overlay area of ​​the
non-modal window to be incorrectly passed to the window below, i.e.
the modal window.
Instead, it would be expected that no action would be taken.

src/ui/manager.cpp

@@ -1457,6 +1457,7 @@ void Manager::_openWindow(Window* window, bool center)
       spec.minimizable(window->isDesktop());
       spec.borderless(!window->isDesktop());
       spec.transparent(window->isTransparent());
+      spec.modal(window->isForeground() || window->isOnTop());
 
       if (!window->isDesktop()) {
         spec.parent(parentDisplay->nativeWindow());