From 06d00b940d167fe9d4b80b999e4c66a4ca5d4e62 Mon Sep 17 00:00:00 2001
From: Matin Aniss <76515905+MatinAniss@users.noreply.github.com>
Date: Mon, 27 Jan 2025 23:07:28 +1100
Subject: [PATCH] gpui: Support windows dark mode title bar (#23700)
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This will allow Windows GPUI applications that utilise the native title
bar to support the dark mode variant when the system user has dark mode
enabled in their system settings. [Related Win32
information](https://learn.microsoft.com/en-us/windows/apps/desktop/modernize/ui/apply-windows-themes)

| Before  | After |
| ------------- | ------------- |
|
![image](https://github.com/user-attachments/assets/50f3d131-8f41-4b91-8012-f8120b150033)
|
![image](https://github.com/user-attachments/assets/a36a6c6b-a469-49ba-85a8-9b55db9ea20f)
|

Release Notes:

- N/A

---------

Co-authored-by: 张小白 <364772080@qq.com>
---
 crates/gpui/src/platform/windows/events.rs |  8 ++++++--
 crates/gpui/src/platform/windows/util.rs   | 18 +++++++++++++++++-
 crates/gpui/src/platform/windows/window.rs |  2 +-
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/crates/gpui/src/platform/windows/events.rs b/crates/gpui/src/platform/windows/events.rs
index 5e0888e82524910d39ea516c86dcaf28f9a6f4ee..4ac573766b3f1f00822066b48a537ff2450777e9 100644
--- a/crates/gpui/src/platform/windows/events.rs
+++ b/crates/gpui/src/platform/windows/events.rs
@@ -89,7 +89,7 @@ pub(crate) fn handle_msg(
         WM_IME_COMPOSITION => handle_ime_composition(handle, lparam, state_ptr),
         WM_SETCURSOR => handle_set_cursor(lparam, state_ptr),
         WM_SETTINGCHANGE => handle_system_settings_changed(handle, state_ptr),
-        WM_DWMCOLORIZATIONCOLORCHANGED => handle_system_theme_changed(state_ptr),
+        WM_DWMCOLORIZATIONCOLORCHANGED => handle_system_theme_changed(handle, state_ptr),
         WM_GPUI_CURSOR_STYLE_CHANGED => handle_cursor_changed(lparam, state_ptr),
         _ => None,
     };
@@ -1215,7 +1215,10 @@ fn handle_system_command(wparam: WPARAM, state_ptr: Rc<WindowsWindowStatePtr>) -
     None
 }
 
-fn handle_system_theme_changed(state_ptr: Rc<WindowsWindowStatePtr>) -> Option<isize> {
+fn handle_system_theme_changed(
+    handle: HWND,
+    state_ptr: Rc<WindowsWindowStatePtr>,
+) -> Option<isize> {
     let mut callback = state_ptr
         .state
         .borrow_mut()
@@ -1224,6 +1227,7 @@ fn handle_system_theme_changed(state_ptr: Rc<WindowsWindowStatePtr>) -> Option<i
         .take()?;
     callback();
     state_ptr.state.borrow_mut().callbacks.appearance_changed = Some(callback);
+    set_dwm_window_appearance(handle);
     Some(0)
 }
 
diff --git a/crates/gpui/src/platform/windows/util.rs b/crates/gpui/src/platform/windows/util.rs
index 5a5408a77b32af4f12ca911bca1872abb77ba8ba..0fa4451db5fdc48fcb7d52b13cb12a95e3bf1e8b 100644
--- a/crates/gpui/src/platform/windows/util.rs
+++ b/crates/gpui/src/platform/windows/util.rs
@@ -3,7 +3,7 @@ use std::sync::OnceLock;
 use ::util::ResultExt;
 use windows::{
     Wdk::System::SystemServices::RtlGetVersion,
-    Win32::{Foundation::*, UI::WindowsAndMessaging::*},
+    Win32::{Foundation::*, Graphics::Dwm::*, UI::WindowsAndMessaging::*},
     UI::{
         Color,
         ViewManagement::{UIColorType, UISettings},
@@ -139,6 +139,22 @@ pub(crate) fn load_cursor(style: CursorStyle) -> HCURSOR {
     }))
 }
 
+pub(crate) fn set_dwm_window_appearance(hwnd: HWND) {
+    let dark_mode_enabled: BOOL = match system_appearance().log_err().unwrap_or_default() {
+        WindowAppearance::Dark | WindowAppearance::VibrantDark => true.into(),
+        WindowAppearance::Light | WindowAppearance::VibrantLight => false.into(),
+    };
+    unsafe {
+        DwmSetWindowAttribute(
+            hwnd,
+            DWMWA_USE_IMMERSIVE_DARK_MODE,
+            &dark_mode_enabled as *const _ as _,
+            std::mem::size_of::<BOOL>() as u32,
+        )
+        .log_err();
+    }
+}
+
 #[inline]
 pub(crate) fn logical_point(x: f32, y: f32, scale_factor: f32) -> Point<Pixels> {
     Point {
diff --git a/crates/gpui/src/platform/windows/window.rs b/crates/gpui/src/platform/windows/window.rs
index 2d873d23bc3fabd2bde3a7f0f991a5c7994ad49f..9dec526d444b85063ab9435d8ff4871aa0cd61eb 100644
--- a/crates/gpui/src/platform/windows/window.rs
+++ b/crates/gpui/src/platform/windows/window.rs
@@ -443,7 +443,7 @@ impl WindowsWindow {
         let state_ptr = context.inner.take().unwrap()?;
         let hwnd = creation_result?;
         register_drag_drop(state_ptr.clone())?;
-
+        set_dwm_window_appearance(hwnd);
         state_ptr.state.borrow_mut().border_offset.update(hwnd)?;
         let placement = retrieve_window_placement(
             hwnd,