fn handle_mouse_moved(&mut self, _new_pos: Point, rel_shift: Point) {
     if let MouseInteractionState::PerformingWindowDrag(dragged_window) =
         &self.mouse_interaction_state
     {
         // We're in the middle of dragging a window
         let prev_frame = dragged_window.frame();
         // Bind the window to the area that windows can be placed within
         let new_frame = self.bind_rect_to_windows_region(
             dragged_window
                 .frame()
                 .replace_origin(dragged_window.frame().origin + rel_shift),
         );
 
         dragged_window.set_frame(new_frame);
+        self.queue_compositor_updates_for_old_and_new_element_frame(prev_frame, new_frame);
         ...
     }
 }

+fn queue_compositor_updates_for_old_and_new_element_frame(
+    &mut self,
+    old_elem_frame: Rect,
+    new_elem_frame: Rect,
+) {
+    let update_rect = old_elem_frame.union(new_elem_frame);
+    if new_elem_frame.intersects_with(old_elem_frame) {
+        // PT: area_excluding_rect() can only give sane results when the input rects overlap
+        for diff_rect in old_elem_frame.area_excluding_rect(new_elem_frame) {
+            self.compositor_state.queue_full_redraw(diff_rect);
+        }
+    } else {
+        self.compositor_state.queue_full_redraw(update_rect);
+    }
+}