Add a way to embed the X11 window into another

Signed-off-by: John Nunley <dev@notgull.net>
Tested-by: Kirill Chibisov <contact@kchibisov.com>

src/platform/x11.rs

@@ -20,6 +20,9 @@ pub type XlibErrorHook =
 /// A unique identifer for an X11 visual.
 pub type XVisualID = u32;
 
+/// A unique identifier for an X11 window.
+pub type XWindow = u32;
+
 /// Hook to winit's xlib error handling callback.
 ///
 /// This method is provided as a safe way to handle the errors comming from X11
@@ -118,18 +121,35 @@ pub trait WindowBuilderExtX11 {
     /// WindowBuilder::new().with_base_size(PhysicalSize::new(400, 200));
     /// ```
     fn with_base_size<S: Into<Size>>(self, base_size: S) -> Self;
+
+    /// Embed this window into another parent window.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use winit::window::WindowBuilder;
+    /// use winit::platform::x11::{XWindow, WindowBuilderExtX11};
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let event_loop = winit::event_loop::EventLoop::new();
+    /// let parent_window_id = std::env::args().nth(1).unwrap().parse::<XWindow>()?;
+    /// let window = WindowBuilder::new()
+    ///     .with_embed_parent_window(parent_window_id)
+    ///     .build(&event_loop)?;
+    /// # Ok(()) }
+    /// ```
+    fn with_embed_parent_window(self, parent_window_id: XWindow) -> Self;
 }
 
 impl WindowBuilderExtX11 for WindowBuilder {
     #[inline]
     fn with_x11_visual(mut self, visual_id: XVisualID) -> Self {
-        self.platform_specific.visual_id = Some(visual_id);
+        self.platform_specific.x11.visual_id = Some(visual_id);
         self
     }
 
     #[inline]
     fn with_x11_screen(mut self, screen_id: i32) -> Self {
-        self.platform_specific.screen_id = Some(screen_id);
+        self.platform_specific.x11.screen_id = Some(screen_id);
         self
     }
 
@@ -141,19 +161,25 @@ impl WindowBuilderExtX11 for WindowBuilder {
 
     #[inline]
     fn with_override_redirect(mut self, override_redirect: bool) -> Self {
-        self.platform_specific.override_redirect = override_redirect;
+        self.platform_specific.x11.override_redirect = override_redirect;
         self
     }
 
     #[inline]
     fn with_x11_window_type(mut self, x11_window_types: Vec<XWindowType>) -> Self {
-        self.platform_specific.x11_window_types = x11_window_types;
+        self.platform_specific.x11.x11_window_types = x11_window_types;
         self
     }
 
     #[inline]
     fn with_base_size<S: Into<Size>>(mut self, base_size: S) -> Self {
-        self.platform_specific.base_size = Some(base_size.into());
+        self.platform_specific.x11.base_size = Some(base_size.into());
+        self
+    }
+
+    #[inline]
+    fn with_embed_parent_window(mut self, parent_window_id: XWindow) -> Self {
+        self.platform_specific.x11.embed_window = Some(parent_window_id);
         self
     }
 }