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.

CHANGELOG.md

@@ -45,6 +45,11 @@ TODO: Add an updates screenshot with some fancy VST3-only plugins to the readme
   and 5.8 required a change, but that change now breaks builds using Wine 6.0
   and up, so this change has been reverted.
 
+### Fixed
+
+- Mostly fixed editor GUIs drifting off to the top or the left when dragging the
+  window off screen in those directions.
+
 ### yabridgectl
 
 - Updated for the changes in yabridge 3.0. Yabridgectl now allows you to set up

src/wine-host/editor.cpp

@@ -376,16 +376,44 @@ void Editor::fix_local_coordinates() const {
     translated_event.response_type = XCB_CONFIGURE_NOTIFY;
     translated_event.event = wine_window;
     translated_event.window = wine_window;
-    // This should be set to the same sizes the window was created on. Since
-    // we're not using `SetWindowPos` to resize the Window, Wine can get a bit
-    // confused when we suddenly report a different client area size. Without
-    // this certain plugins (such as those by Valhalla DSP) would break.
+    // This should be set to the same sizes the window was created on. Wine can
+    // get a bit confused when we suddenly report a different client area size.
+    // Without this certain plugins (such as those by Valhalla DSP) would break.
     translated_event.width = client_area.width;
     translated_event.height = client_area.height;
     translated_event.x = translated_coordinates->dst_x;
     translated_event.y = translated_coordinates->dst_y;
     free(translated_coordinates);
 
+    // When the window gets dragged off to the left or top corner of the screen
+    // a lot of plugin's GUIs start to drift off in the wrong direction when we
+    // send these negative coordinates in a ConfigureNotify event. To somewhat
+    // work around this, we'll move the Wine window to offset these changes.
+    // Since this could in theory cause other weird behaviour, we'll only undo
+    // these changes (by moving the window back to `(0, 0)`) once.
+    int correction_x = 0;
+    int correction_y = 0;
+    if (translated_event.x < 0) {
+        correction_x = -translated_event.x;
+    }
+    if (translated_event.y < 0) {
+        correction_y = -translated_event.y;
+    }
+
+    if (correction_x != 0 || correction_y != 0) {
+        SetWindowPos(
+            get_win32_handle(), nullptr, correction_x, correction_y, 0, 0,
+            SWP_NOACTIVATE | SWP_NOOWNERZORDER | SWP_NOSIZE | SWP_NOZORDER);
+        has_negative_coordinate_correction = true;
+    } else if (has_negative_coordinate_correction.compare_exchange_strong(
+                   const_cast<bool&>(static_cast<const bool&>(true)), false)) {
+        // Undo this only once, since who knows what side effects this might
+        // cause
+        SetWindowPos(
+            get_win32_handle(), nullptr, 0, 0, 0, 0,
+            SWP_NOACTIVATE | SWP_NOOWNERZORDER | SWP_NOSIZE | SWP_NOZORDER);
+    }
+
     xcb_send_event(
         x11_connection.get(), false, wine_window,
         XCB_EVENT_MASK_STRUCTURE_NOTIFY | XCB_EVENT_MASK_SUBSTRUCTURE_NOTIFY,

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`.
      */