On Windows and macOS, add API to enable/disable window controls (#2537)

* On Windows and macOS, add API to enable/disable window controls

* fix build

* missing import

* use `WindowButtons` flags

* rename to `[set_]enabled_buttons`

* add example, fix windows impl for minimize

* macOS: Fix button enabling close/minimize while disabling maximized

* Update src/platform_impl/windows/window.rs

Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

* compose the flags on a sep line, use `bool::then`

Co-authored-by: Mads Marquart <mads@marquart.dk>
Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

src/platform_impl/macos/appkit/control.rs

@@ -1,5 +1,5 @@
 use objc2::foundation::NSObject;
-use objc2::{extern_class, ClassType};
+use objc2::{extern_class, extern_methods, ClassType};
 
 use super::{NSResponder, NSView};
 
@@ -12,3 +12,13 @@ extern_class!(
         type Super = NSView;
     }
 );
+
+extern_methods!(
+    unsafe impl NSControl {
+        #[sel(setEnabled:)]
+        pub fn setEnabled(&self, enabled: bool);
+
+        #[sel(isEnabled)]
+        pub fn isEnabled(&self) -> bool;
+    }
+);

src/platform_impl/macos/appkit/window.rs

@@ -180,6 +180,12 @@ extern_methods!(
         #[sel(isResizable)]
         pub fn isResizable(&self) -> bool;
 
+        #[sel(isMiniaturizable)]
+        pub fn isMiniaturizable(&self) -> bool;
+
+        #[sel(hasCloseBox)]
+        pub fn hasCloseBox(&self) -> bool;
+
         #[sel(isMiniaturized)]
         pub fn isMiniaturized(&self) -> bool;
 

src/platform_impl/macos/window.rs

@@ -29,7 +29,7 @@ use crate::{
         Fullscreen, OsError,
     },
     window::{
-        CursorGrabMode, CursorIcon, Theme, UserAttentionType, WindowAttributes,
+        CursorGrabMode, CursorIcon, Theme, UserAttentionType, WindowAttributes, WindowButtons,
         WindowId as RootWindowId, WindowLevel,
     },
 };
@@ -269,6 +269,14 @@ impl WinitWindow {
                 masks &= !NSWindowStyleMask::NSResizableWindowMask;
             }
 
+            if !attrs.enabled_buttons.contains(WindowButtons::MINIMIZE) {
+                masks &= !NSWindowStyleMask::NSMiniaturizableWindowMask;
+            }
+
+            if !attrs.enabled_buttons.contains(WindowButtons::CLOSE) {
+                masks &= !NSWindowStyleMask::NSClosableWindowMask;
+            }
+
             if pl_attrs.fullsize_content_view {
                 masks |= NSWindowStyleMask::NSFullSizeContentViewWindowMask;
             }
@@ -333,6 +341,12 @@ impl WinitWindow {
                     this.setMovableByWindowBackground(true);
                 }
 
+                if !attrs.enabled_buttons.contains(WindowButtons::MAXIMIZE) {
+                    if let Some(button) = this.standardWindowButton(NSWindowButton::Zoom) {
+                        button.setEnabled(false);
+                    }
+                }
+
                 if let Some(increments) = attrs.resize_increments {
                     let increments = increments.to_logical(this.scale_factor());
                     let (w, h) = (increments.width, increments.height);
@@ -624,6 +638,53 @@ impl WinitWindow {
         self.isResizable()
     }
 
+    #[inline]
+    pub fn set_enabled_buttons(&self, buttons: WindowButtons) {
+        let mut mask = self.styleMask();
+
+        if buttons.contains(WindowButtons::CLOSE) {
+            mask |= NSWindowStyleMask::NSClosableWindowMask;
+        } else {
+            mask &= !NSWindowStyleMask::NSClosableWindowMask;
+        }
+
+        if buttons.contains(WindowButtons::MINIMIZE) {
+            mask |= NSWindowStyleMask::NSMiniaturizableWindowMask;
+        } else {
+            mask &= !NSWindowStyleMask::NSMiniaturizableWindowMask;
+        }
+
+        // This must happen before the button's "enabled" status has been set,
+        // hence we do it synchronously.
+        self.set_style_mask_sync(mask);
+
+        // We edit the button directly instead of using `NSResizableWindowMask`,
+        // since that mask also affect the resizability of the window (which is
+        // controllable by other means in `winit`).
+        if let Some(button) = self.standardWindowButton(NSWindowButton::Zoom) {
+            button.setEnabled(buttons.contains(WindowButtons::MAXIMIZE));
+        }
+    }
+
+    #[inline]
+    pub fn enabled_buttons(&self) -> WindowButtons {
+        let mut buttons = WindowButtons::empty();
+        if self.isMiniaturizable() {
+            buttons |= WindowButtons::MINIMIZE;
+        }
+        if self
+            .standardWindowButton(NSWindowButton::Zoom)
+            .map(|b| b.isEnabled())
+            .unwrap_or(true)
+        {
+            buttons |= WindowButtons::MAXIMIZE;
+        }
+        if self.hasCloseBox() {
+            buttons |= WindowButtons::CLOSE;
+        }
+        buttons
+    }
+
     pub fn set_cursor_icon(&self, icon: CursorIcon) {
         let view = self.view();
         let mut cursor_state = view.state.cursor_state.lock().unwrap();