Add option to enable/disable WS_CLIPCHILDREN window style (#3212)

CHANGELOG.md

@@ -91,6 +91,7 @@ Unreleased` header.
 - On macOS, send a `Resized` event after each `ScaleFactorChanged` event.
 - On Wayland, fix `wl_surface` being destroyed before associated objects.
 - On macOS, fix assertion when pressing `Fn` key.
+- On Windows, add `WindowBuilderExtWindows::with_clip_children` to control `WS_CLIPCHILDREN` style.
 
 # 0.29.3
 

src/platform/windows.rs

@@ -315,6 +315,9 @@ pub trait WindowBuilderExtWindows {
     /// Enabling the shadow causes a thin 1px line to appear on the top of the window.
     fn with_undecorated_shadow(self, shadow: bool) -> Self;
 
+    /// This sets or removes `WS_CLIPCHILDREN` style.
+    fn with_clip_children(self, flag: bool) -> Self;
+
     /// Sets the color of the window border.
     ///
     /// Supported starting with Windows 11 Build 22000.
@@ -385,6 +388,12 @@ impl WindowBuilderExtWindows for WindowBuilder {
         self
     }
 
+    #[inline]
+    fn with_clip_children(mut self, flag: bool) -> Self {
+        self.window.platform_specific.clip_children = flag;
+        self
+    }
+
     #[inline]
     fn with_border_color(mut self, color: Option<Color>) -> Self {
         self.window.platform_specific.border_color = Some(color.unwrap_or(Color::NONE));

src/platform_impl/windows/mod.rs

@@ -37,6 +37,7 @@ pub struct PlatformSpecificWindowBuilderAttributes {
     pub skip_taskbar: bool,
     pub class_name: String,
     pub decoration_shadow: bool,
+    pub clip_children: bool,
     pub border_color: Option<Color>,
     pub title_background_color: Option<Color>,
     pub title_text_color: Option<Color>,
@@ -54,6 +55,7 @@ impl Default for PlatformSpecificWindowBuilderAttributes {
             skip_taskbar: false,
             class_name: "Window Class".to_string(),
             decoration_shadow: false,
+            clip_children: true,
             border_color: None,
             title_background_color: None,
             title_text_color: None,

src/platform_impl/windows/window.rs

@@ -1356,6 +1356,10 @@ unsafe fn init(
     // Will be changed later using `window.set_enabled_buttons` but we need to set a default here
     // so the diffing later can work.
     window_flags.set(WindowFlags::CLOSABLE, true);
+    window_flags.set(
+        WindowFlags::CLIP_CHILDREN,
+        attributes.platform_specific.clip_children,
+    );
 
     let mut fallback_parent = || match attributes.platform_specific.owner {
         Some(parent) => {

src/platform_impl/windows/window_state.rs

@@ -124,6 +124,8 @@ bitflags! {
 
         const MARKER_ACTIVATE = 1 << 21;
 
+        const CLIP_CHILDREN = 1 << 22;
+
         const EXCLUSIVE_FULLSCREEN_OR_MASK = WindowFlags::ALWAYS_ON_TOP.bits();
     }
 }
@@ -253,7 +255,7 @@ impl WindowFlags {
 
     pub fn to_window_styles(self) -> (WINDOW_STYLE, WINDOW_EX_STYLE) {
         // Required styles to properly support common window functionality like aero snap.
-        let mut style = WS_CAPTION | WS_BORDER | WS_CLIPSIBLINGS | WS_CLIPCHILDREN | WS_SYSMENU;
+        let mut style = WS_CAPTION | WS_BORDER | WS_CLIPSIBLINGS | WS_SYSMENU;
         let mut style_ex = WS_EX_WINDOWEDGE | WS_EX_ACCEPTFILES;
 
         if self.contains(WindowFlags::RESIZABLE) {
@@ -298,6 +300,9 @@ impl WindowFlags {
         if self.contains(WindowFlags::IGNORE_CURSOR_EVENT) {
             style_ex |= WS_EX_TRANSPARENT | WS_EX_LAYERED;
         }
+        if self.contains(WindowFlags::CLIP_CHILDREN) {
+            style |= WS_CLIPCHILDREN;
+        }
 
         if self.intersects(
             WindowFlags::MARKER_EXCLUSIVE_FULLSCREEN | WindowFlags::MARKER_BORDERLESS_FULLSCREEN,