actually create nspanels for dialogs.

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

@@ -29,7 +29,6 @@
 @implementation CLASS_NAME
 {
     ComPtr<WindowBaseImpl> _parent;
-    bool _canBecomeKeyAndMain;
     bool _closed;
     bool _isEnabled;
     bool _isExtended;
@@ -157,11 +156,6 @@
     _menu = menu;
 }
 
--(void) setCanBecomeKeyAndMain
-{
-    _canBecomeKeyAndMain = true;
-}
-
 -(CLASS_NAME*)  initWithParent: (WindowBaseImpl*) parent contentRect: (NSRect)contentRect styleMask: (NSWindowStyleMask)styleMask;
 {
     // https://jameshfisher.com/2020/07/10/why-is-the-contentrect-of-my-nswindow-ignored/
@@ -215,28 +209,27 @@
 
 -(BOOL)canBecomeKeyWindow
 {
-    if (_canBecomeKeyAndMain)
+    // 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])
     {
-        // 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);
-            if(ch == nil)
-                continue;
-            if (ch.isDialog)
-                return false;
-        }
-
-        return true;
+        // TODO protocol
+        auto ch = objc_cast<CLASS_NAME>(uch);
+        if(ch == nil)
+            continue;
+        if (ch.isDialog)
+            return false;
     }
 
-    return false;
+    return true;
 }
 
 -(BOOL)canBecomeMainWindow
 {
-    return _canBecomeKeyAndMain;
+#ifdef IS_NSPANEL
+    return false;
+#else
+    return true;
+#endif
 }
 
 -(bool)shouldTryToHandleEvents

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

@@ -122,6 +122,7 @@ protected:
     id<AvnWindowProtocol> GetWindowProtocol ();
 
 private:
+    void CreateNSWindow (bool isDialog);
     void InitialiseNSWindow ();
 };
 

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

@@ -13,6 +13,7 @@
 #include "AutoFitContentView.h"
 #import "WindowProtocol.h"
 #import "WindowInterfaces.h"
+#include "WindowBaseImpl.h"
 
 
 WindowBaseImpl::~WindowBaseImpl() {
@@ -31,6 +32,9 @@ WindowBaseImpl::WindowBaseImpl(IAvnWindowBaseEvents *events, IAvnGlContext *gl)
 
     lastPositionSet.X = 100;
     lastPositionSet.Y = 100;
+    lastSize = NSSize { 100, 100 };
+    lastMaxSize = NSSize { CGFLOAT_MAX, CGFLOAT_MAX};
+    lastMinSize = NSSize { 0, 0 };
     _lastTitle = @"";
 
     Window = nullptr;
@@ -85,6 +89,7 @@ HRESULT WindowBaseImpl::Show(bool activate, bool isDialog) {
     START_COM_CALL;
 
     @autoreleasepool {
+        CreateNSWindow(isDialog);
         InitialiseNSWindow();
 
         SetPosition(lastPositionSet);
@@ -92,10 +97,6 @@ HRESULT WindowBaseImpl::Show(bool activate, bool isDialog) {
 
         [Window setTitle:_lastTitle];
 
-        if(!isDialog) {
-            [GetWindowProtocol() setCanBecomeKeyAndMain];
-        }
-
         if (ShouldTakeFocusOnShow() && activate) {
             [Window orderFront:Window];
             [Window makeKeyAndOrderFront:Window];
@@ -524,9 +525,21 @@ void WindowBaseImpl::UpdateStyle() {
     [Window setStyleMask:GetStyle()];
 }
 
-void WindowBaseImpl::InitialiseNSWindow() {
+void WindowBaseImpl::CreateNSWindow(bool isDialog) {
     if(Window == nullptr) {
-        Window = [[AvnWindow alloc] initWithParent:this contentRect:NSRect{0, 0, lastSize} styleMask:GetStyle()];
+        if(isDialog)
+        {
+            Window = [[AvnPanel alloc] initWithParent:this contentRect:NSRect{0, 0, lastSize} styleMask:GetStyle()];
+        }
+        else
+        {
+            Window = [[AvnWindow alloc] initWithParent:this contentRect:NSRect{0, 0, lastSize} styleMask:GetStyle()];
+        }
+    }
+}
+
+void WindowBaseImpl::InitialiseNSWindow() {
+    if(Window != nullptr) {
         [Window setContentView:StandardContainer];
         [Window setStyleMask:NSWindowStyleMaskBorderless];
         [Window setBackingType:NSBackingStoreBuffered];
@@ -537,9 +550,6 @@ void WindowBaseImpl::InitialiseNSWindow() {
 
         [Window setOpaque:false];
 
-        [Window setContentMinSize:lastMinSize];
-        [Window setContentMaxSize:lastMaxSize];
-
         if (lastMenu != nullptr) {
             [GetWindowProtocol() applyMenu:lastMenu];
 

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

@@ -507,7 +507,7 @@ bool WindowImpl::IsDialog() {
 }
 
 NSWindowStyleMask WindowImpl::GetStyle() {
-    unsigned long s = NSWindowStyleMaskBorderless;
+    unsigned long s = this->_isDialog ? NSWindowStyleMaskUtilityWindow : NSWindowStyleMaskBorderless;
 
     switch (_decorations) {
         case SystemDecorationsNone:

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

@@ -10,7 +10,6 @@
 @class AvnMenu;
 
 @protocol AvnWindowProtocol
--(void) setCanBecomeKeyAndMain;
 -(void) pollModalSession: (NSModalSession _Nonnull) session;
 -(void) restoreParentWindow;
 -(bool) shouldTryToHandleEvents;