Improve theme change at runtime (#1473)

* Improve theme change at runtime

* Handle change to dark mode

* Refactor theme calculation

* Ensure theme is updated for WM_ACTIVATE and WM_SETTINGCHANGE events

v2/internal/frontend/desktop/windows/frontend.go

@@ -106,28 +106,15 @@ func (f *Frontend) WindowReload() {
 }
 
 func (f *Frontend) WindowSetSystemDefaultTheme() {
-	f.mainWindow.frontendOptions.Windows.Theme = windows.SystemDefault
+	f.mainWindow.SetTheme(windows.SystemDefault)
-	f.mainWindow.Invoke(func() {
-		f.mainWindow.updateTheme()
-	})
 }
 
 func (f *Frontend) WindowSetLightTheme() {
-	if f.mainWindow.frontendOptions != nil && f.mainWindow.frontendOptions.Windows != nil {
+	f.mainWindow.SetTheme(windows.Light)
-		f.mainWindow.frontendOptions.Windows.Theme = windows.Light
-		f.mainWindow.Invoke(func() {
-			f.mainWindow.updateTheme()
-		})
-	}
 }
 
 func (f *Frontend) WindowSetDarkTheme() {
-	if f.mainWindow.frontendOptions != nil && f.mainWindow.frontendOptions.Windows != nil {
+	f.mainWindow.SetTheme(windows.Dark)
-		f.mainWindow.frontendOptions.Windows.Theme = windows.Dark
-		f.mainWindow.Invoke(func() {
-			f.mainWindow.updateTheme()
-		})
-	}
 }
 
 func (f *Frontend) Run(ctx context.Context) error {

v2/internal/frontend/desktop/windows/theme.go

@@ -7,6 +7,12 @@ import (
 
 func (w *Window) updateTheme() {
 
+	// Don't redraw theme if nothing has changed
+	if !w.themeChanged {
+		return
+	}
+	w.themeChanged = false
+
 	if win32.IsCurrentlyHighContrastMode() {
 		return
 	}
@@ -14,25 +20,24 @@ func (w *Window) updateTheme() {
 	if !win32.SupportsThemes() {
 		return
 	}
-	// Only process if there's a theme change
-	isDarkMode := win32.IsCurrentlyDarkMode()
-	w.isDarkMode = isDarkMode
 
-	// Default use system theme
+	var isDarkMode bool
+	switch w.theme {
+	case windows.SystemDefault:
+		isDarkMode = win32.IsCurrentlyDarkMode()
+	case windows.Dark:
+		isDarkMode = true
+	case windows.Light:
+		isDarkMode = false
+	}
+	win32.SetTheme(w.Handle(), isDarkMode)
+
+	// Custom theme processing
 	winOptions := w.frontendOptions.Windows
 	var customTheme *windows.ThemeSettings
 	if winOptions != nil {
 		customTheme = winOptions.CustomTheme
-		if winOptions.Theme == windows.Dark {
-			isDarkMode = true
-		}
-		if winOptions.Theme == windows.Light {
-			isDarkMode = false
-		}
 	}
-
-	win32.SetTheme(w.Handle(), isDarkMode)
-
 	// Custom theme
 	if win32.SupportsCustomThemes() && customTheme != nil {
 		if w.isActive {

v2/internal/frontend/desktop/windows/window.go

@@ -12,6 +12,7 @@ import (
 	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/winc/w32"
 	"github.com/wailsapp/wails/v2/pkg/menu"
 	"github.com/wailsapp/wails/v2/pkg/options"
+	winoptions "github.com/wailsapp/wails/v2/pkg/options/windows"
 )
 
 type Window struct {
@@ -24,6 +25,11 @@ type Window struct {
 	isDarkMode                               bool
 	isActive                                 bool
 	hasBeenShown                             bool
+
+	// Theme
+	theme        winoptions.Theme
+	themeChanged bool
+
 	OnSuspend                                func()
 	OnResume                                 func()
 }
@@ -37,6 +43,7 @@ func NewWindow(parent winc.Controller, appoptions *options.App, versionInfo *ope
 		maxWidth:        appoptions.MaxWidth,
 		versionInfo:     versionInfo,
 		isActive:        true,
+		themeChanged:    true,
 	}
 	result.SetIsForm(true)
 
@@ -73,6 +80,16 @@ func NewWindow(parent winc.Controller, appoptions *options.App, versionInfo *ope
 		win32.SetBackgroundColour(result.Handle(), appoptions.BackgroundColour.R, appoptions.BackgroundColour.G, appoptions.BackgroundColour.B)
 	}
 
+	if appoptions.Windows != nil {
+		result.theme = appoptions.Windows.Theme
+	} else {
+		result.theme = winoptions.SystemDefault
+	}
+
+	if appoptions.BackgroundColour != nil {
+		win32.SetBackgroundColour(result.Handle(), appoptions.BackgroundColour.R, appoptions.BackgroundColour.G, appoptions.BackgroundColour.B)
+	}
+
 	result.SetSize(appoptions.Width, appoptions.Height)
 	result.SetText(appoptions.Title)
 	result.EnableSizable(!appoptions.DisableResize)
@@ -163,6 +180,7 @@ func (w *Window) WndProc(msg uint32, wparam, lparam uintptr) uintptr {
 	case w32.WM_SETTINGCHANGE:
 		settingChanged := w32.UTF16PtrToString((*uint16)(unsafe.Pointer(lparam)))
 		if settingChanged == "ImmersiveColorSet" {
+			w.themeChanged = true
 			w.updateTheme()
 		}
 		return 0
@@ -174,6 +192,7 @@ func (w *Window) WndProc(msg uint32, wparam, lparam uintptr) uintptr {
 		}
 	case w32.WM_ACTIVATE:
 		//if !w.frontendOptions.Frameless {
+		w.themeChanged = true
 		if int(wparam) == w32.WA_INACTIVE {
 			w.isActive = false
 			w.updateTheme()
@@ -262,3 +281,11 @@ func (w *Window) IsMaximised() bool {
 func (w *Window) IsMinimised() bool {
 	return win32.IsWindowMinimised(w.Handle())
 }
+
+func (w *Window) SetTheme(theme winoptions.Theme) {
+	w.theme = theme
+	w.themeChanged = true
+	w.Invoke(func() {
+		w.updateTheme()
+	})
+}