Ability to force a theme on Windows (#1666)

src/platform_impl/windows/window.rs

@@ -34,7 +34,7 @@ use crate::{
     icon::Icon,
     monitor::MonitorHandle as RootMonitorHandle,
     platform_impl::platform::{
-        dark_mode::try_dark_mode,
+        dark_mode::try_theme,
         dpi::{dpi_to_scale_factor, hwnd_dpi},
         drop_handler::FileDropHandler,
         event_loop::{self, EventLoopWindowTarget, DESTROY_MSG_ID},
@@ -43,7 +43,7 @@ use crate::{
         window_state::{CursorFlags, SavedWindow, WindowFlags, WindowState},
         PlatformSpecificWindowBuilderAttributes, WindowId,
     },
-    window::{CursorIcon, Fullscreen, UserAttentionType, WindowAttributes},
+    window::{CursorIcon, Fullscreen, Theme, UserAttentionType, WindowAttributes},
 };
 
 /// The Win32 implementation of the main `Window` object.
@@ -653,8 +653,8 @@ impl Window {
     }
 
     #[inline]
-    pub fn is_dark_mode(&self) -> bool {
-        self.window_state.lock().is_dark_mode
+    pub fn theme(&self) -> Theme {
+        self.window_state.lock().current_theme
     }
 }
 
@@ -764,14 +764,15 @@ unsafe fn init<T: 'static>(
     // If the system theme is dark, we need to set the window theme now
     // before we update the window flags (and possibly show the
     // window for the first time).
-    let dark_mode = try_dark_mode(real_window.0);
+    let current_theme = try_theme(real_window.0, pl_attribs.preferred_theme);
 
     let window_state = {
         let window_state = WindowState::new(
             &attributes,
             pl_attribs.taskbar_icon,
             scale_factor,
-            dark_mode,
+            current_theme,
+            pl_attribs.preferred_theme,
         );
         let window_state = Arc::new(Mutex::new(window_state));
         WindowState::set_window_flags(window_state.lock(), real_window.0, |f| *f = window_flags);