feat(macOS): Allow creation of child Window (#160)

.changes/parent-support.md

@@ -0,0 +1,5 @@
+---
+"tao": patch
+---
+
+macOS: Add `with_parent_window()` on `WindowBuilder`.

examples/parentwindow.rs

@@ -0,0 +1,62 @@
+// Copyright 2019-2021 Tauri Programme within The Commons Conservancy
+// SPDX-License-Identifier: Apache-2.0
+
+#[cfg(any(target_os = "windows", target_os = "macos"))]
+fn main() {
+  use simple_logger::SimpleLogger;
+  use std::collections::HashMap;
+  #[cfg(target_os = "macos")]
+  use tao::platform::macos::{WindowBuilderExtMacOS, WindowExtMacOS};
+  #[cfg(target_os = "windows")]
+  use tao::platform::windows::{WindowBuilderExtWindows, WindowExtWindows};
+  use tao::{
+    dpi::LogicalSize,
+    event::{Event, StartCause, WindowEvent},
+    event_loop::{ControlFlow, EventLoop},
+    window::WindowBuilder,
+  };
+  #[cfg(target_os = "windows")]
+  use winapi::shared::windef::HWND;
+  SimpleLogger::new().init().unwrap();
+  let event_loop = EventLoop::new();
+  let mut windows = HashMap::new();
+  let main_window = WindowBuilder::new().build(&event_loop).unwrap();
+
+  #[cfg(target_os = "macos")]
+  let parent_window = main_window.ns_window();
+  #[cfg(target_os = "windows")]
+  let parent_window = main_window.hwnd() as HWND;
+
+  let child_window = WindowBuilder::new()
+    .with_parent_window(parent_window)
+    .with_inner_size(LogicalSize::new(200, 200))
+    .build(&event_loop)
+    .unwrap();
+
+  windows.insert(child_window.id(), child_window);
+  windows.insert(main_window.id(), main_window);
+
+  event_loop.run(move |event, _, control_flow| {
+    *control_flow = ControlFlow::Wait;
+
+    match event {
+      Event::NewEvents(StartCause::Init) => println!("TAO application started!"),
+      Event::WindowEvent {
+        event, window_id, ..
+      } if event == WindowEvent::CloseRequested => {
+        println!("Window {:?} has received the signal to close", window_id);
+        // This drop the window, causing it to close.
+        windows.remove(&window_id);
+        if windows.is_empty() {
+          *control_flow = ControlFlow::Exit;
+        }
+      }
+      _ => (),
+    };
+  })
+}
+
+#[cfg(not(any(target_os = "windows", target_os = "macos")))]
+fn main() {
+  println!("This platform doesn't have the parent window support.");
+}

src/platform/macos.rs

@@ -10,7 +10,7 @@ use crate::{
   event_loop::{EventLoop, EventLoopWindowTarget},
   menu::CustomMenuItem,
   monitor::MonitorHandle,
-  platform_impl::get_aux_state_mut,
+  platform_impl::{get_aux_state_mut, Parent},
   window::{Window, WindowBuilder},
 };
 
@@ -304,6 +304,8 @@ impl NativeImage {
 ///  - `with_titlebar_buttons_hidden`
 ///  - `with_fullsize_content_view`
 pub trait WindowBuilderExtMacOS {
+  /// Sets a parent to the window to be created.
+  fn with_parent_window(self, parent: *mut c_void) -> WindowBuilder;
   /// Enables click-and-drag behavior for the entire window, not just the titlebar.
   fn with_movable_by_window_background(self, movable_by_window_background: bool) -> WindowBuilder;
   /// Makes the titlebar transparent and allows the content to appear behind it.
@@ -323,6 +325,12 @@ pub trait WindowBuilderExtMacOS {
 }
 
 impl WindowBuilderExtMacOS for WindowBuilder {
+  #[inline]
+  fn with_parent_window(mut self, parent: *mut c_void) -> WindowBuilder {
+    self.platform_specific.parent = Parent::ChildOf(parent);
+    self
+  }
+
   #[inline]
   fn with_movable_by_window_background(
     mut self,

src/platform_impl/macos/mod.rs

@@ -36,7 +36,7 @@ pub use self::{
   keycode::{keycode_from_scancode, keycode_to_scancode},
   menu::{Menu, MenuItemAttributes},
   monitor::{MonitorHandle, VideoMode},
-  window::{Id as WindowId, PlatformSpecificWindowBuilderAttributes, UnownedWindow},
+  window::{Id as WindowId, Parent, PlatformSpecificWindowBuilderAttributes, UnownedWindow},
 };
 use crate::{
   error::OsError as RootOsError, event::DeviceId as RootDeviceId, window::WindowAttributes,

src/platform_impl/macos/window.rs

@@ -34,7 +34,8 @@ use crate::{
 use cocoa::{
   appkit::{
     self, CGFloat, NSApp, NSApplication, NSApplicationPresentationOptions, NSColor,
-    NSRequestUserAttentionType, NSScreen, NSView, NSWindow, NSWindowButton, NSWindowStyleMask,
+    NSRequestUserAttentionType, NSScreen, NSView, NSWindow, NSWindowButton, NSWindowOrderingMode,
+    NSWindowStyleMask,
   },
   base::{id, nil},
   foundation::{NSAutoreleasePool, NSDictionary, NSPoint, NSRect, NSSize},
@@ -62,8 +63,16 @@ pub fn get_window_id(window_cocoa_id: id) -> Id {
   Id(window_cocoa_id as *const Object as _)
 }
 
+#[non_exhaustive]
+#[derive(Clone)]
+pub enum Parent {
+  None,
+  ChildOf(*mut c_void),
+}
+
 #[derive(Clone)]
 pub struct PlatformSpecificWindowBuilderAttributes {
+  pub parent: Parent,
   pub movable_by_window_background: bool,
   pub titlebar_transparent: bool,
   pub title_hidden: bool,
@@ -79,6 +88,7 @@ impl Default for PlatformSpecificWindowBuilderAttributes {
   #[inline]
   fn default() -> Self {
     Self {
+      parent: Parent::None,
       movable_by_window_background: false,
       titlebar_transparent: false,
       title_hidden: false,
@@ -229,6 +239,10 @@ fn create_window(
         }
       }
 
+      if let Parent::ChildOf(parent) = pl_attrs.parent {
+        let _: () = msg_send![parent as id, addChildWindow: *ns_window ordered: NSWindowOrderingMode::NSWindowAbove];
+      }
+
       if !pl_attrs.has_shadow {
         ns_window.setHasShadow_(NO);
       }