Mostly fix editor GUIs drifting in negative coords

I think some rounding in Wine is causing this issue, but then again
we're not supposed to send these ConfigureNotify events to the window
directly anyways.

src/wine-host/editor.h

@@ -250,6 +250,17 @@ class Editor {
      */
     const xcb_window_t topmost_window;
 
+    /**
+     * In `fix_local_coordinates()` we send a ConfigureNotify event to the Wine
+     * window with its screen coordinates. Because you're not supposed to do
+     * that directly, we're getting some strange behaviour on some plugins when
+     * the window gets dragged off screen to the left or the top. We perform a
+     * small workaround to mostly correct this issue. This flag indicates
+     * whether we have done this in the last call to `fix_local_coordinates()`,
+     * since we only only need to undo the changes made there once.
+     */
+    mutable std::atomic_bool has_negative_coordinate_correction = false;
+
     /**
      * The atom corresponding to `_NET_ACTIVE_WINDOW`.
      */