macOS: add ability to make titlebar unified (rust-windowing#3960)

Adds `WindowExtMacOS::set_unified_titlebar` and
`WindowAttributesExtMacOS::with_unified_titlebar`,
which allow you to use a larger titlebar style on macOS.

Cargo.toml

@@ -136,6 +136,7 @@ objc2-app-kit = { version = "0.2.2", features = [
     "NSScreen",
     "NSTextInputClient",
     "NSTextInputContext",
+    "NSToolbar",
     "NSView",
     "NSWindow",
     "NSWindowScripting",

src/changelog/unreleased.md

@@ -64,6 +64,8 @@ changelog entry.
 - Add a `standard_key_binding` method to the `ApplicationHandlerExtMacOS` trait. This allows handling of standard keybindings such as "go to end of line" on macOS.
 - On macOS, add `WindowExtMacOS::set_borderless_game` and `WindowAttributesExtMacOS::with_borderless_game`
   to fully disable the menu bar and dock in Borderless Fullscreen as commonly done in games.
+- On macOS, add `WindowExtMacOS::set_unified_titlebar` and `WindowAttributesExtMacOS::with_unified_titlebar`
+  to use a larger style of titlebar.
 - Add `WindowId::into_raw()` and `from_raw()`.
 - Add `PointerKind`, `PointerSource`, `ButtonSource`, `FingerId` and `position` to all pointer
   events as part of the pointer event overhaul.

src/platform/macos.rs

@@ -157,6 +157,13 @@ pub trait WindowExtMacOS {
 
     /// Getter for the [`WindowExtMacOS::set_borderless_game`].
     fn is_borderless_game(&self) -> bool;
+
+    /// Makes the titlebar bigger, effectively adding more space around the
+    /// window controls if the titlebar is invisible.
+    fn set_unified_titlebar(&self, unified_titlebar: bool);
+
+    /// Getter for the [`WindowExtMacOS::set_unified_titlebar`].
+    fn unified_titlebar(&self) -> bool;
 }
 
 impl WindowExtMacOS for dyn Window + '_ {
@@ -255,6 +262,18 @@ impl WindowExtMacOS for dyn Window + '_ {
         let window = self.as_any().downcast_ref::<crate::platform_impl::Window>().unwrap();
         window.maybe_wait_on_main(|w| w.is_borderless_game())
     }
+
+    #[inline]
+    fn set_unified_titlebar(&self, unified_titlebar: bool) {
+        let window = self.as_any().downcast_ref::<crate::platform_impl::Window>().unwrap();
+        window.maybe_wait_on_main(|w| w.set_unified_titlebar(unified_titlebar))
+    }
+
+    #[inline]
+    fn unified_titlebar(&self) -> bool {
+        let window = self.as_any().downcast_ref::<crate::platform_impl::Window>().unwrap();
+        window.maybe_wait_on_main(|w| w.unified_titlebar())
+    }
 }
 
 /// Corresponds to `NSApplicationActivationPolicy`.
@@ -308,6 +327,8 @@ pub trait WindowAttributesExtMacOS {
     fn with_option_as_alt(self, option_as_alt: OptionAsAlt) -> Self;
     /// See [`WindowExtMacOS::set_borderless_game`] for details on what this means if set.
     fn with_borderless_game(self, borderless_game: bool) -> Self;
+    /// See [`WindowExtMacOS::set_unified_titlebar`] for details on what this means if set.
+    fn with_unified_titlebar(self, unified_titlebar: bool) -> Self;
 }
 
 impl WindowAttributesExtMacOS for WindowAttributes {
@@ -382,6 +403,12 @@ impl WindowAttributesExtMacOS for WindowAttributes {
         self.platform_specific.borderless_game = borderless_game;
         self
     }
+
+    #[inline]
+    fn with_unified_titlebar(mut self, unified_titlebar: bool) -> Self {
+        self.platform_specific.unified_titlebar = unified_titlebar;
+        self
+    }
 }
 
 pub trait EventLoopBuilderExtMacOS {

src/platform_impl/apple/appkit/window_delegate.rs

@@ -15,9 +15,10 @@ use objc2_app_kit::{
     NSAppKitVersionNumber, NSAppKitVersionNumber10_12, NSAppearance, NSAppearanceCustomization,
     NSAppearanceNameAqua, NSApplication, NSApplicationPresentationOptions, NSBackingStoreType,
     NSColor, NSDraggingDestination, NSFilenamesPboardType, NSPasteboard,
-    NSRequestUserAttentionType, NSScreen, NSView, NSWindowButton, NSWindowDelegate,
+    NSRequestUserAttentionType, NSScreen, NSToolbar, NSView, NSWindowButton, NSWindowDelegate,
     NSWindowFullScreenButton, NSWindowLevel, NSWindowOcclusionState, NSWindowOrderingMode,
     NSWindowSharingType, NSWindowStyleMask, NSWindowTabbingMode, NSWindowTitleVisibility,
+    NSWindowToolbarStyle,
 };
 use objc2_foundation::{
     ns_string, CGFloat, MainThreadMarker, NSArray, NSCopying, NSDictionary, NSKeyValueChangeKey,
@@ -57,6 +58,7 @@ pub struct PlatformSpecificWindowAttributes {
     pub tabbing_identifier: Option<String>,
     pub option_as_alt: OptionAsAlt,
     pub borderless_game: bool,
+    pub unified_titlebar: bool,
 }
 
 impl Default for PlatformSpecificWindowAttributes {
@@ -75,6 +77,7 @@ impl Default for PlatformSpecificWindowAttributes {
             tabbing_identifier: None,
             option_as_alt: Default::default(),
             borderless_game: false,
+            unified_titlebar: false,
         }
     }
 }
@@ -616,6 +619,14 @@ fn new_window(
         if attrs.platform_specific.movable_by_window_background {
             window.setMovableByWindowBackground(true);
         }
+        if attrs.platform_specific.unified_titlebar {
+            unsafe {
+                // The toolbar style is ignored if there is no toolbar, so it is
+                // necessary to add one.
+                window.setToolbar(Some(&NSToolbar::new(mtm)));
+                window.setToolbarStyle(NSWindowToolbarStyle::Unified);
+            }
+        }
 
         if !attrs.enabled_buttons.contains(WindowButtons::MAXIMIZE) {
             if let Some(button) = window.standardWindowButton(NSWindowButton::NSWindowZoomButton) {
@@ -1837,6 +1848,34 @@ impl WindowExtMacOS for WindowDelegate {
     fn is_borderless_game(&self) -> bool {
         self.ivars().is_borderless_game.get()
     }
+
+    fn set_unified_titlebar(&self, unified_titlebar: bool) {
+        let window = self.window();
+
+        if unified_titlebar {
+            let mtm = MainThreadMarker::from(self);
+
+            unsafe {
+                // The toolbar style is ignored if there is no toolbar, so it is
+                // necessary to add one.
+                window.setToolbar(Some(&NSToolbar::new(mtm)));
+                window.setToolbarStyle(NSWindowToolbarStyle::Unified);
+            }
+        } else {
+            unsafe {
+                window.setToolbar(None);
+                window.setToolbarStyle(NSWindowToolbarStyle::Automatic);
+            }
+        }
+    }
+
+    fn unified_titlebar(&self) -> bool {
+        let window = self.window();
+
+        unsafe {
+            window.toolbar().is_some() && window.toolbarStyle() == NSWindowToolbarStyle::Unified
+        }
+    }
 }
 
 const DEFAULT_STANDARD_FRAME: NSRect =