Merge pull request #335 from and3md/queue_widget_destroy

Queue widget destroy support

src/dlangui/core/events.d

@@ -1649,6 +1649,25 @@ class RunnableEvent : CustomEvent {
     }
 }
 
+/**
+Queue destroy event.
+
+This event allows delayed widget destruction and is used internally by 
+$(LINK2 $(DDOX_ROOT_DIR)dlangui/platforms/common/platform/Window.queueWidgetDestroy.html, Window.queueWidgetDestroy()).
+*/
+class QueueDestroyEvent : RunnableEvent {
+    private Widget _widgetToDestroy;
+    this (Widget widgetToDestroy)
+    {
+        _widgetToDestroy = widgetToDestroy;
+        super(1,null, delegate void () {
+            if (_widgetToDestroy.parent) 
+                _widgetToDestroy.parent.removeChild(_widgetToDestroy);
+            destroy(_widgetToDestroy);
+        });
+    }
+}
+
 interface CustomEventTarget {
     /// post event to handle in UI thread (this method can be used from background thread)
     void postEvent(CustomEvent event);

src/dlangui/platforms/common/platform.d

@@ -519,7 +519,24 @@ class Window : CustomEventTarget {
         destroy(_timerQueue);
         _eventList = null;
     }
-
+    
+    /**
+    Allows queue destroy of widget.
+    
+    Sometimes when you have very complicated UI with dynamic create/destroy lists of widgets calling simple destroy() 
+    on widget makes segmentation fault.
+    
+    Usually because you destroy widget that on some stage call another that tries to destroy widget that calls it.
+    When the control flow returns widget not exist and you have seg. fault.
+    
+    This function use internally $(LINK2 $(DDOX_ROOT_DIR)dlangui/core/events/QueueDestroyEvent.html, QueueDestroyEvent).
+    */
+    void queueWidgetDestroy(Widget widgetToDestroy)
+    {
+        QueueDestroyEvent ev = new QueueDestroyEvent(widgetToDestroy);
+        postEvent(ev);
+    }
+    
     private void animate(Widget root, long interval) {
         if (root is null)
             return;