On Windows, expose DWM attributes (#3409)

CHANGELOG.md

@@ -33,6 +33,7 @@ Unreleased` header.
 - Add the `OwnedDisplayHandle` type for allowing safe display handle usage outside of trivial cases.
 - **Breaking:** Rename `TouchpadMagnify` to `PinchGesture`, `SmartMagnify` to `DoubleTapGesture` and `TouchpadRotate` to `RotationGesture` to represent the action rather than the intent.
 - on iOS, add detection support for `PinchGesture`, `DoubleTapGesture` and `RotationGesture`.
+- on Windows: add `with_border_color`, `with_title_background_color`, `with_title_text_color` and `with_corner_preference`
 
 # 0.29.10
 

FEATURES.md

@@ -126,6 +126,10 @@ If your PR makes notable changes to Winit's features, please update this section
 * Setting a menu bar
 * `WS_EX_NOREDIRECTIONBITMAP` support
 * Theme the title bar according to Windows 10 Dark Mode setting or set a preferred theme
+* Setting the window border color
+* Setting the title bar background color
+* Setting the title color
+* Setting the corner rounding preference
 
 ### macOS
 * Window activation policy

src/platform/windows.rs

@@ -15,6 +15,60 @@ pub type HMENU = isize;
 /// Monitor Handle type used by Win32 API
 pub type HMONITOR = isize;
 
+/// Describes a color used by Windows
+#[repr(transparent)]
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub struct Color(u32);
+
+impl Color {
+    /// Use the system's default color
+    pub const SYSTEM_DEFAULT: Color = Color(0xFFFFFFFF);
+
+    //Special constant only valid for the window border and therefore modeled using Option<Color> for user facing code
+    const NONE: Color = Color(0xFFFFFFFE);
+
+    /// Create a new color from the given RGB values
+    pub const fn from_rgb(r: u8, g: u8, b: u8) -> Self {
+        Self((r as u32) | ((g as u32) << 8) | ((b as u32) << 16))
+    }
+}
+
+impl Default for Color {
+    fn default() -> Self {
+        Self::SYSTEM_DEFAULT
+    }
+}
+
+/// Describes how the corners of a window should look like.
+///
+/// For a detailed explanation, see [`DWM_WINDOW_CORNER_PREFERENCE docs`].
+///
+/// [`DWM_WINDOW_CORNER_PREFERENCE docs`]: https://learn.microsoft.com/en-us/windows/win32/api/dwmapi/ne-dwmapi-dwm_window_corner_preference
+#[repr(i32)]
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum CornerPreference {
+    /// Corresponds to `DWMWCP_DEFAULT`.
+    ///
+    /// Let the system decide when to round window corners.
+    #[default]
+    Default = 0,
+
+    /// Corresponds to `DWMWCP_DONOTROUND`.
+    ///
+    /// Never round window corners.
+    DoNotRound = 1,
+
+    /// Corresponds to `DWMWCP_ROUND`.
+    ///
+    /// Round the corners, if appropriate.
+    Round = 2,
+
+    /// Corresponds to `DWMWCP_ROUNDSMALL`.
+    ///
+    /// Round the corners if appropriate, with a small radius.
+    RoundSmall = 3,
+}
+
 /// Additional methods on `EventLoop` that are specific to Windows.
 pub trait EventLoopBuilderExtWindows {
     /// Whether to allow the event loop to be created off of the main thread.
@@ -133,6 +187,26 @@ pub trait WindowExtWindows {
     ///
     /// Enabling the shadow causes a thin 1px line to appear on the top of the window.
     fn set_undecorated_shadow(&self, shadow: bool);
+
+    /// Sets the color of the window border.
+    ///
+    /// Supported starting with Windows 11 Build 22000.
+    fn set_border_color(&self, color: Option<Color>);
+
+    /// Sets the background color of the title bar.
+    ///
+    /// Supported starting with Windows 11 Build 22000.
+    fn set_title_background_color(&self, color: Option<Color>);
+
+    /// Sets the color of the window title.
+    ///
+    /// Supported starting with Windows 11 Build 22000.
+    fn set_title_text_color(&self, color: Color);
+
+    /// Sets the preferred style of the window corners.
+    ///
+    /// Supported starting with Windows 11 Build 22000.
+    fn set_corner_preference(&self, preference: CornerPreference);
 }
 
 impl WindowExtWindows for Window {
@@ -155,6 +229,29 @@ impl WindowExtWindows for Window {
     fn set_undecorated_shadow(&self, shadow: bool) {
         self.window.set_undecorated_shadow(shadow)
     }
+
+    #[inline]
+    fn set_border_color(&self, color: Option<Color>) {
+        self.window.set_border_color(color.unwrap_or(Color::NONE))
+    }
+
+    #[inline]
+    fn set_title_background_color(&self, color: Option<Color>) {
+        // The windows docs don't mention NONE as a valid options but it works in practice and is useful
+        // to circumvent the Windows option "Show accent color on title bars and window borders"
+        self.window
+            .set_title_background_color(color.unwrap_or(Color::NONE))
+    }
+
+    #[inline]
+    fn set_title_text_color(&self, color: Color) {
+        self.window.set_title_text_color(color)
+    }
+
+    #[inline]
+    fn set_corner_preference(&self, preference: CornerPreference) {
+        self.window.set_corner_preference(preference)
+    }
 }
 
 /// Additional methods on `WindowBuilder` that are specific to Windows.
@@ -217,6 +314,26 @@ pub trait WindowBuilderExtWindows {
     /// The shadow is hidden by default.
     /// Enabling the shadow causes a thin 1px line to appear on the top of the window.
     fn with_undecorated_shadow(self, shadow: bool) -> Self;
+
+    /// Sets the color of the window border.
+    ///
+    /// Supported starting with Windows 11 Build 22000.
+    fn with_border_color(self, color: Option<Color>) -> Self;
+
+    /// Sets the background color of the title bar.
+    ///
+    /// Supported starting with Windows 11 Build 22000.
+    fn with_title_background_color(self, color: Option<Color>) -> Self;
+
+    /// Sets the color of the window title.
+    ///
+    /// Supported starting with Windows 11 Build 22000.
+    fn with_title_text_color(self, color: Color) -> Self;
+
+    /// Sets the preferred style of the window corners.
+    ///
+    /// Supported starting with Windows 11 Build 22000.
+    fn with_corner_preference(self, corners: CornerPreference) -> Self;
 }
 
 impl WindowBuilderExtWindows for WindowBuilder {
@@ -267,6 +384,30 @@ impl WindowBuilderExtWindows for WindowBuilder {
         self.window.platform_specific.decoration_shadow = shadow;
         self
     }
+
+    #[inline]
+    fn with_border_color(mut self, color: Option<Color>) -> Self {
+        self.window.platform_specific.border_color = Some(color.unwrap_or(Color::NONE));
+        self
+    }
+
+    #[inline]
+    fn with_title_background_color(mut self, color: Option<Color>) -> Self {
+        self.window.platform_specific.title_background_color = Some(color.unwrap_or(Color::NONE));
+        self
+    }
+
+    #[inline]
+    fn with_title_text_color(mut self, color: Color) -> Self {
+        self.window.platform_specific.title_text_color = Some(color);
+        self
+    }
+
+    #[inline]
+    fn with_corner_preference(mut self, corners: CornerPreference) -> Self {
+        self.window.platform_specific.corner_preference = Some(corners);
+        self
+    }
 }
 
 /// Additional methods on `MonitorHandle` that are specific to Windows.

src/platform_impl/windows/mod.rs

@@ -25,6 +25,7 @@ use crate::platform_impl::Fullscreen;
 use crate::event::DeviceId as RootDeviceId;
 use crate::icon::Icon;
 use crate::keyboard::Key;
+use crate::platform::windows::{Color, CornerPreference};
 
 #[derive(Clone, Debug)]
 pub struct PlatformSpecificWindowBuilderAttributes {
@@ -36,6 +37,10 @@ pub struct PlatformSpecificWindowBuilderAttributes {
     pub skip_taskbar: bool,
     pub class_name: String,
     pub decoration_shadow: bool,
+    pub border_color: Option<Color>,
+    pub title_background_color: Option<Color>,
+    pub title_text_color: Option<Color>,
+    pub corner_preference: Option<CornerPreference>,
 }
 
 impl Default for PlatformSpecificWindowBuilderAttributes {
@@ -49,6 +54,10 @@ impl Default for PlatformSpecificWindowBuilderAttributes {
             skip_taskbar: false,
             class_name: "Window Class".to_string(),
             decoration_shadow: false,
+            border_color: None,
+            title_background_color: None,
+            title_text_color: None,
+            corner_preference: None,
         }
     }
 }

src/platform_impl/windows/window.rs

@@ -14,7 +14,11 @@ use windows_sys::Win32::{
         HWND, LPARAM, OLE_E_WRONGCOMPOBJ, POINT, POINTS, RECT, RPC_E_CHANGED_MODE, S_OK, WPARAM,
     },
     Graphics::{
-        Dwm::{DwmEnableBlurBehindWindow, DWM_BB_BLURREGION, DWM_BB_ENABLE, DWM_BLURBEHIND},
+        Dwm::{
+            DwmEnableBlurBehindWindow, DwmSetWindowAttribute, DWMWA_BORDER_COLOR,
+            DWMWA_CAPTION_COLOR, DWMWA_TEXT_COLOR, DWMWA_WINDOW_CORNER_PREFERENCE,
+            DWM_BB_BLURREGION, DWM_BB_ENABLE, DWM_BLURBEHIND, DWM_WINDOW_CORNER_PREFERENCE,
+        },
         Gdi::{
             ChangeDisplaySettingsExW, ClientToScreen, CreateRectRgn, DeleteObject, InvalidateRgn,
             RedrawWindow, CDS_FULLSCREEN, DISP_CHANGE_BADFLAGS, DISP_CHANGE_BADMODE,
@@ -56,6 +60,7 @@ use windows_sys::Win32::{
 
 use log::warn;
 
+use crate::platform::windows::{Color, CornerPreference};
 use crate::{
     cursor::Cursor,
     dpi::{PhysicalPosition, PhysicalSize, Position, Size},
@@ -1060,6 +1065,54 @@ impl Window {
             );
         }
     }
+
+    #[inline]
+    pub fn set_border_color(&self, color: Color) {
+        unsafe {
+            DwmSetWindowAttribute(
+                self.hwnd(),
+                DWMWA_BORDER_COLOR,
+                &color as *const _ as _,
+                mem::size_of::<Color>() as _,
+            );
+        }
+    }
+
+    #[inline]
+    pub fn set_title_background_color(&self, color: Color) {
+        unsafe {
+            DwmSetWindowAttribute(
+                self.hwnd(),
+                DWMWA_CAPTION_COLOR,
+                &color as *const _ as _,
+                mem::size_of::<Color>() as _,
+            );
+        }
+    }
+
+    #[inline]
+    pub fn set_title_text_color(&self, color: Color) {
+        unsafe {
+            DwmSetWindowAttribute(
+                self.hwnd(),
+                DWMWA_TEXT_COLOR,
+                &color as *const _ as _,
+                mem::size_of::<Color>() as _,
+            );
+        }
+    }
+
+    #[inline]
+    pub fn set_corner_preference(&self, preference: CornerPreference) {
+        unsafe {
+            DwmSetWindowAttribute(
+                self.hwnd(),
+                DWMWA_WINDOW_CORNER_PREFERENCE,
+                &(preference as DWM_WINDOW_CORNER_PREFERENCE) as *const _ as _,
+                mem::size_of::<DWM_WINDOW_CORNER_PREFERENCE>() as _,
+            );
+        }
+    }
 }
 
 impl Drop for Window {
@@ -1265,6 +1318,19 @@ impl<'a> InitData<'a> {
         if let Some(position) = attributes.position {
             win.set_outer_position(position);
         }
+
+        if let Some(color) = self.attributes.platform_specific.border_color {
+            win.set_border_color(color);
+        }
+        if let Some(color) = self.attributes.platform_specific.title_background_color {
+            win.set_title_background_color(color);
+        }
+        if let Some(color) = self.attributes.platform_specific.title_text_color {
+            win.set_title_text_color(color);
+        }
+        if let Some(corner) = self.attributes.platform_specific.corner_preference {
+            win.set_corner_preference(corner);
+        }
     }
 }
 unsafe fn init(