iOS: Remove QUIView from superview on QIOSWindow destruction

Unlike on macOS, our UIViews are children of a QIOSDesktopManagerView
that we use to do window management, so we need to remove the view
from its superview, even if represents a top level QWindow.

The only exception is top level foreign windows, which are used to
represent a native UIView for the purpose of containing a Qt view
hierarchy within. As we don't know anything about the foreign view's
superview hiearchy we shouldn't touch it.

Fixes: QTBUG-120369
Change-Id: I6a43bb0a4e72d0d1525a7cc33d572ea7477215b3
Reviewed-by: Doris Verria <doris.verria@qt.io>
(cherry picked from commit bc7e728fcfd2cfdbff29fa9d1b0f8dae718a0f8c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 34e3bdcb5e99dcae07b8c7749faeb798af21233b)

1 files changed, 5 insertions, 4 deletions

diff --git a/src/plugins/platforms/ios/qioswindow.mm b/src/plugins/platforms/ios/qioswindow.mm
index 1d682ff897..db72bdfc80 100644
--- a/src/plugins/platforms/ios/qioswindow.mm
+++ b/src/plugins/platforms/ios/qioswindow.mm
@@ -90,11 +90,12 @@ QIOSWindow::~QIOSWindow()
 
     clearAccessibleCache();
 
-    quiview_cast(m_view).platformWindow = 0;
+    quiview_cast(m_view).platformWindow = nullptr;
 
-    // Remove from superview only if we have a Qt window parent,
-    // as we don't want to affect window container foreign windows.
-    if (QPlatformWindow::parent())
+    // Remove from superview, unless we're a foreign window without a
+    // Qt window parent, in which case the foreign window is used as
+    // a window container for a Qt UI hierarchy inside a native UI.
+    if (!(isForeignWindow() && !QPlatformWindow::parent()))
         [m_view removeFromSuperview];
 
     [m_view release];