Fix hang when reparenting a frozen window in wxOSX

The wrong order of changing parent and freezing/thawing could result in
hanging the application when reparenting frozen windows, e.g. when
switching order of pages in a notebook.

Closes #16722.

src/osx/cocoa/window.mm

@@ -769,6 +769,30 @@ void wxWidgetCocoaImpl::SetupMouseEvent( wxMouseEvent &wxevent , NSEvent * nsEve
     }
 }
 
+static void SetDrawingEnabledIfFrozenRecursive(wxWidgetCocoaImpl *impl, bool enable)
+{
+    if (!impl->GetWXPeer())
+        return;
+
+    if (impl->GetWXPeer()->IsFrozen())
+        impl->SetDrawingEnabled(enable);
+
+    for ( wxWindowList::iterator i = impl->GetWXPeer()->GetChildren().begin();
+          i != impl->GetWXPeer()->GetChildren().end();
+          ++i )
+    {
+        wxWindow *child = *i;
+        if ( child->IsTopLevel() || !child->IsFrozen() )
+            continue;
+
+        // Skip any user panes as they'll handle this themselves
+        if ( !child->GetPeer() || child->GetPeer()->IsUserPane() )
+            continue;
+
+        SetDrawingEnabledIfFrozenRecursive((wxWidgetCocoaImpl *)child->GetPeer(), enable);
+    }
+}
+
 @implementation wxNSView
 
 + (void)initialize
@@ -887,6 +911,24 @@ void wxWidgetCocoaImpl::SetupMouseEvent( wxMouseEvent &wxevent , NSEvent * nsEve
     return [super hitTest:aPoint];
 }
 
+- (void) viewWillMoveToWindow:(NSWindow *)newWindow
+{
+    wxWidgetCocoaImpl* viewimpl = (wxWidgetCocoaImpl*) wxWidgetImpl::FindFromWXWidget( self );
+    if (viewimpl)
+        SetDrawingEnabledIfFrozenRecursive(viewimpl, true);
+
+    [super viewWillMoveToWindow:newWindow];
+}
+
+- (void) viewDidMoveToWindow
+{
+    wxWidgetCocoaImpl* viewimpl = (wxWidgetCocoaImpl*) wxWidgetImpl::FindFromWXWidget( self );
+    if (viewimpl)
+        SetDrawingEnabledIfFrozenRecursive(viewimpl, false);
+
+    [super viewDidMoveToWindow];
+}
+
 @end // wxNSView
 
 // We need to adopt NSTextInputClient protocol in order to interpretKeyEvents: to work.
@@ -2486,7 +2528,7 @@ void wxWidgetCocoaImpl::Init()
 wxWidgetCocoaImpl::~wxWidgetCocoaImpl()
 {
     if ( GetWXPeer() && GetWXPeer()->IsFrozen() )
-        [[m_osxView window] enableFlushWindow];
+        SetDrawingEnabled(true);
     
     RemoveAssociations( this );
 
@@ -3034,6 +3076,10 @@ void wxWidgetCocoaImpl::SetDropTarget(wxDropTarget* target)
 
 void wxWidgetCocoaImpl::RemoveFromParent()
 {
+    // User panes will be thawed in the removeFromSuperview call below
+    if (!IsUserPane() && m_wxPeer->IsFrozen())
+        SetDrawingEnabled(true);
+
     [m_osxView removeFromSuperview];
 }
 
@@ -3043,8 +3089,9 @@ void wxWidgetCocoaImpl::Embed( wxWidgetImpl *parent )
     wxASSERT_MSG( container != NULL , wxT("No valid mac container control") ) ;
     [container addSubview:m_osxView];
     
-    if( m_wxPeer->IsFrozen() )
-        [[m_osxView window] disableFlushWindow];
+    // User panes will be frozen elsewhere
+    if( m_wxPeer->IsFrozen() && !IsUserPane() )
+        SetDrawingEnabled(false);
 }
 
 void wxWidgetCocoaImpl::SetBackgroundColour( const wxColour &col )
@@ -3693,6 +3740,9 @@ void wxWidgetCocoaImpl::SetFlipped(bool flipped)
 
 void wxWidgetCocoaImpl::SetDrawingEnabled(bool enabled)
 {
+    if ( [m_osxView window] == nil )
+        return;
+
     if ( enabled )
     {
         [[m_osxView window] enableFlushWindow];