Sub windows (squashed from previous branch)

CHANGELOG.md

@@ -8,6 +8,8 @@ You can find its changes [documented below](#070---2021-01-01).
 ### Highlights
 
 ### Added
+- Sub windows: Allow opening windows that share state with arbitrary parts of the widget hierarchy ([#1254] by [@rjwittams])
+- WindowCloseRequested/WindowDisconnected event when a window is closing ([#1254] by [@rjwittams])
 
 ### Changed
 

druid-shell/src/platform/mac/window.rs

@@ -419,6 +419,10 @@ lazy_static! {
             sel!(showContextMenu:),
             show_context_menu as extern "C" fn(&mut Object, Sel, id),
         );
+        decl.add_method(
+            sel!(windowShouldClose:),
+            window_should_close as extern "C" fn(&mut Object, Sel, id)->BOOL,
+        );
         decl.add_method(
             sel!(windowWillClose:),
             window_will_close as extern "C" fn(&mut Object, Sel, id),
@@ -827,7 +831,16 @@ extern "C" fn window_did_resign_key(this: &mut Object, _: Sel, _notification: id
     }
 }
 
-extern "C" fn window_will_close(this: &mut Object, _: Sel, _window: id) {
+extern "C" fn window_should_close(this: &mut Object, _: Sel, _window: id) -> BOOL {
+    unsafe {
+        let view_state: *mut c_void = *this.get_ivar("viewState");
+        let view_state = &mut *(view_state as *mut ViewState);
+        (*view_state).handler.request_close();
+        NO
+    }
+}
+
+extern "C" fn window_will_close(this: &mut Object, _: Sel, _notification: id) {
     unsafe {
         let view_state: *mut c_void = *this.get_ivar("viewState");
         let view_state = &mut *(view_state as *mut ViewState);