stdin.patch

diff --git i/src/plugins/platforms/cocoa/qcocoawindow.mm w/src/plugins/platforms/cocoa/qcocoawindow.mm
index cb813114ef8..be2efdae110 100644
--- i/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ w/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -134,16 +134,18 @@ void QCocoaWindow::initialize()
     if (!m_view)
         m_view = [[QNSView alloc] initWithCocoaWindow:this];
 
-    // Compute the initial geometry based on the geometry set on the
-    // QWindow. This geometry has already been reflected to the
-    // QPlatformWindow in the constructor, so to ensure that the
-    // resulting setGeometry call does not think the geometry has
-    // already been applied, we reset the QPlatformWindow's view
-    // of the geometry first.
-    auto initialGeometry = QPlatformWindow::initialGeometry(window(),
-        windowGeometry(), defaultWindowWidth, defaultWindowHeight);
-    QPlatformWindow::d_ptr->rect = QRect();
-    setGeometry(initialGeometry);
+    if (!isForeignWindow()) {
+        // Compute the initial geometry based on the geometry set on the
+        // QWindow. This geometry has already been reflected to the
+        // QPlatformWindow in the constructor, so to ensure that the
+        // resulting setGeometry call does not think the geometry has
+        // already been applied, we reset the QPlatformWindow's view
+        // of the geometry first.
+        auto initialGeometry = QPlatformWindow::initialGeometry(window(),
+            windowGeometry(), defaultWindowWidth, defaultWindowHeight);
+        QPlatformWindow::d_ptr->rect = QRect();
+        setGeometry(initialGeometry);
+    }
 
     recreateWindowIfNeeded();
 
@@ -1468,7 +1470,7 @@ void QCocoaWindow::recreateWindowIfNeeded()
 
     const bool shouldBeContentView = !parentWindow
         && !((type & Qt::SubWindow) == Qt::SubWindow)
-        && !isEmbeddedView;
+        && !isEmbeddedView && !isForeignWindow();
     if (isContentView() != shouldBeContentView)
         recreateReason |= ContentViewChanged;
 

@pmogylevskyi are the builtin Apple Audio Units working for you in your app ? I am able to load / view NSView for most third party ones but some of the apples ones crash AUBandPass being the first example.
It is definitely to do with using QWindow::fromWinId() + QWidget::createWindowContainer() if I just do QWindow::fromWinId() and show that window it works fine, as soon as I add QWidget::createWindowContainer() to embed in a widget hierarchy (we need preset selection etc right) it crashes.