Add a knob to specify a class for window creation.

This is useful to allow overriding some behaviours that are not
sent to WindowsDelegate (for example canBecomeKey, etc). Will default to
NSWindow so it will be a noop for existing code.

src/appkit/window/class.rs

@@ -227,8 +227,8 @@ extern "C" fn cancel<T: WindowDelegate>(this: &Object, _: Sel, _: id) {
 
 /// Injects an `NSWindowDelegate` subclass, with some callback and pointer ivars for what we
 /// need to do.
-pub(crate) fn register_window_class_with_delegate<T: WindowDelegate>(instance: &T) -> *const Class {
-    load_or_register_class("NSWindow", instance.subclass_name(), |decl| unsafe {
+pub(crate) fn register_window_class_with_delegate<T: WindowDelegate>(class_name: &'static str, instance: &T) -> *const Class {
+    load_or_register_class(class_name, instance.subclass_name(), |decl| unsafe {
         decl.add_ivar::<usize>(WINDOW_DELEGATE_PTR);
 
         // NSWindowDelegate methods

src/appkit/window/config.rs

@@ -2,6 +2,9 @@
 //! mask). This configuration object acts as a way to orchestrate enabling customization before the
 //! window object is created - it's returned in your `WindowDelegate` object.
 
+use objc::class;
+use objc::runtime::Class;
+
 use crate::appkit::window::enums::{WindowStyle, WindowToolbarStyle};
 use crate::foundation::NSUInteger;
 use crate::geometry::Rect;
@@ -32,7 +35,11 @@ pub struct WindowConfig {
     /// for other variants.
     ///
     /// This setting is notably important for Preferences windows.
-    pub toolbar_style: WindowToolbarStyle
+    pub toolbar_style: WindowToolbarStyle,
+
+    /// The base class to use for Window construction, by default will be
+    /// NSWindow but you can use any class here that inherits from NSWindow.
+    pub window_class: &'static Class,
 }
 
 impl Default for WindowConfig {
@@ -41,7 +48,8 @@ impl Default for WindowConfig {
             style: 0,
             initial_dimensions: Rect::new(100., 100., 1024., 768.),
             defer: true,
-            toolbar_style: WindowToolbarStyle::Automatic
+            toolbar_style: WindowToolbarStyle::Automatic,
+            window_class: class!(NSWindow),
         };
 
         config.set_styles(&[
@@ -83,4 +91,8 @@ impl WindowConfig {
     pub fn set_toolbar_style(&mut self, style: WindowToolbarStyle) {
         self.toolbar_style = style;
     }
+
+    pub fn set_window_class(&mut self, cls : &'static Class) {
+        self.window_class = cls;
+    }
 }

src/appkit/window/mod.rs

@@ -70,9 +70,9 @@ impl Window {
         let objc = unsafe {
             // This behavior might make sense to keep as default (YES), but I think the majority of
             // apps that would use this toolkit wouldn't be tab-oriented...
-            let _: () = msg_send![class!(NSWindow), setAllowsAutomaticWindowTabbing: NO];
+            let _: () = msg_send![config.window_class, setAllowsAutomaticWindowTabbing: NO];
 
-            let alloc: id = msg_send![class!(NSWindow), alloc];
+            let alloc: id = msg_send![config.window_class, alloc];
 
             // Other types of backing (Retained/NonRetained) are archaic, dating back to the
             // NeXTSTEP era, and are outright deprecated... so we don't allow setting them.
@@ -131,13 +131,13 @@ where
     /// enables easier structure of your codebase, and in a way simulates traditional class based
     /// architectures... just without the subclassing.
     pub fn with(config: WindowConfig, delegate: T) -> Self {
-        let class = register_window_class_with_delegate::<T>(&delegate);
+        let class = register_window_class_with_delegate::<T>(config.window_class.name(), &delegate);
         let mut delegate = Box::new(delegate);
 
         let objc = unsafe {
             // This behavior might make sense to keep as default (YES), but I think the majority of
             // apps that would use this toolkit wouldn't be tab-oriented...
-            let _: () = msg_send![class!(NSWindow), setAllowsAutomaticWindowTabbing: NO];
+            let _: () = msg_send![config.window_class, setAllowsAutomaticWindowTabbing: NO];
 
             let alloc: id = msg_send![class, alloc];