ensure cast to protocol instead of concrete types.

native/Avalonia.Native/src/OSX/AutoFitContentView.mm

@@ -5,7 +5,8 @@
 
 #include "AvnView.h"
 #include "AutoFitContentView.h"
-#import "WindowInterfaces.h"
+#include "WindowInterfaces.h"
+#include "WindowProtocol.h"
 
 @implementation AutoFitContentView
 {
@@ -84,7 +85,7 @@
     _settingSize = true;
     [super setFrameSize:newSize];
 
-    auto window = objc_cast<AvnWindow>([self window]);
+    auto window = static_cast<id <AvnWindowProtocol>>([self window]);
 
     // TODO get actual titlebar size
 

native/Avalonia.Native/src/OSX/AvnView.mm

@@ -195,7 +195,12 @@
 
 - (bool) ignoreUserInput:(bool)trigerInputWhenDisabled
 {
-    auto parentWindow = objc_cast<AvnWindow>([self window]);
+    if(_parent == nullptr)
+    {
+        return TRUE;
+    }
+
+    auto parentWindow = _parent->GetWindowProtocol();
 
     if(parentWindow == nil || ![parentWindow shouldTryToHandleEvents])
     {

native/Avalonia.Native/src/OSX/AvnWindow.mm

@@ -212,8 +212,7 @@
     // If the window has a child window being shown as a dialog then don't allow it to become the key window.
     for(NSWindow* uch in [self childWindows])
     {
-        // TODO protocol
-        auto ch = objc_cast<CLASS_NAME>(uch);
+        auto ch = static_cast<id <AvnWindowProtocol>>(uch);
         if(ch == nil)
             continue;
         if (ch.isDialog)
@@ -256,8 +255,7 @@
 
 -(void) restoreParentWindow;
 {
-    // TODO protocol
-    auto parent = objc_cast<CLASS_NAME>([self parentWindow]);
+    auto parent = static_cast<id <AvnWindowProtocol>>([self parentWindow]);
     if(parent != nil)
     {
         [parent removeChildWindow:self];

native/Avalonia.Native/src/OSX/WindowBaseImpl.h

@@ -114,13 +114,13 @@ BEGIN_INTERFACE_MAP()
 
     virtual bool IsDialog();
 
+    id<AvnWindowProtocol> GetWindowProtocol ();
+
 protected:
     virtual NSWindowStyleMask GetStyle();
 
     void UpdateStyle();
 
-    id<AvnWindowProtocol> GetWindowProtocol ();
-
 private:
     void CreateNSWindow (bool isDialog);
     void InitialiseNSWindow ();

native/Avalonia.Native/src/OSX/WindowBaseImpl.mm

@@ -561,12 +561,12 @@ void WindowBaseImpl::InitialiseNSWindow() {
 }
 
 id <AvnWindowProtocol> WindowBaseImpl::GetWindowProtocol() {
-    id instance;
-    if ([Window conformsToProtocol:@protocol(AvnWindowProtocol)]) {
-        instance = Window;
+    if(Window == nullptr)
+    {
+        return nullptr;
     }
 
-    return instance;
+    return static_cast<id <AvnWindowProtocol>>(Window);
 }
 
 extern IAvnWindow* CreateAvnWindow(IAvnWindowEvents*events, IAvnGlContext* gl)