[Feature/1149] Dark mode (#1281)

* Add Windows version helper

* Initial theme support

* Support custom themes

* Update docs

* Honour HighContrast theme. Remove import "C". Refactor

* Small refactor

* Support inactive theme

* Update Docs

v2/go.mod

@@ -27,7 +27,7 @@ require (
 	github.com/leaanthony/idgen v1.0.0
 	github.com/leaanthony/slicer v1.5.0
 	github.com/leaanthony/typescriptify-golang-structs v0.1.7
-	github.com/leaanthony/winc v0.0.0-20220208061147-37b059b9dc3b
+	github.com/leaanthony/winc v0.0.0-20220323084916-ea5df694ec1f
 	github.com/leaanthony/winicon v1.0.0
 	github.com/matryer/is v1.4.0
 	github.com/olekukonko/tablewriter v0.0.4

v2/go.sum

@@ -130,6 +130,8 @@ github.com/leaanthony/typescriptify-golang-structs v0.1.7 h1:yoznzWzyxkO/iWdlpq+
 github.com/leaanthony/typescriptify-golang-structs v0.1.7/go.mod h1:cWtOkiVhMF77e6phAXUcfNwYmMwCJ67Sij24lfvi9Js=
 github.com/leaanthony/winc v0.0.0-20220208061147-37b059b9dc3b h1:cJ+VfVwX3GkRGSy0SiOyZ7FjSGMPAY/rS/wJzilo23I=
 github.com/leaanthony/winc v0.0.0-20220208061147-37b059b9dc3b/go.mod h1:OPfk8SNMAKRcSv8Vw1QL0yupmwcRtJyXZUgtMoaHUGc=
+github.com/leaanthony/winc v0.0.0-20220323084916-ea5df694ec1f h1:RM0TNQXGTt06ZrSysdo+r9E9fk1ObACFBOww+W1zOiU=
+github.com/leaanthony/winc v0.0.0-20220323084916-ea5df694ec1f/go.mod h1:OPfk8SNMAKRcSv8Vw1QL0yupmwcRtJyXZUgtMoaHUGc=
 github.com/leaanthony/winicon v1.0.0 h1:ZNt5U5dY71oEoKZ97UVwJRT4e+5xo5o/ieKuHuk8NqQ=
 github.com/leaanthony/winicon v1.0.0/go.mod h1:en5xhijl92aphrJdmRPlh4NI1L6wq3gEm0LpXAPghjU=
 github.com/leodido/go-urn v1.2.0 h1:hpXL4XnriNwQ/ABnpepYM/1vCLWNDfUNts8dX3xTG6Y=

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

@@ -7,6 +7,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"github.com/wailsapp/wails/v2/internal/system/operatingsystem"
 	"log"
 	"runtime"
 	"strconv"
@@ -45,10 +46,16 @@ type Frontend struct {
 	servingFromDisk bool
 
 	hasStarted bool
+
+	// Windows build number
+	versionInfo *operatingsystem.WindowsVersionInfo
 }
 
 func NewFrontend(ctx context.Context, appoptions *options.App, myLogger *logger.Logger, appBindings *binding.Bindings, dispatcher frontend.Dispatcher) *Frontend {
 
+	// Get Windows build number
+	versionInfo, _ := operatingsystem.GetWindowsVersionInfo()
+
 	result := &Frontend{
 		frontendOptions: appoptions,
 		logger:          myLogger,
@@ -56,6 +63,7 @@ func NewFrontend(ctx context.Context, appoptions *options.App, myLogger *logger.
 		dispatcher:      dispatcher,
 		ctx:             ctx,
 		startURL:        "http://wails.localhost/",
+		versionInfo:     versionInfo,
 	}
 
 	bindingsJSON, err := appBindings.ToJSON()
@@ -99,7 +107,7 @@ func (f *Frontend) Run(ctx context.Context) error {
 
 	f.ctx = context.WithValue(ctx, "frontend", f)
 
-	mainWindow := NewWindow(nil, f.frontendOptions)
+	mainWindow := NewWindow(nil, f.frontendOptions, f.versionInfo)
 	f.mainWindow = mainWindow
 
 	var _debug = ctx.Value("debug")

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

@@ -48,8 +48,10 @@ func processMenu(window *Window, menu *menu.Menu) {
 	mainMenu := window.NewMenu()
 	for _, menuItem := range menu.Items {
 		submenu := mainMenu.AddSubMenu(menuItem.Label)
-		for _, menuItem := range menuItem.SubMenu.Items {
+		if menuItem.SubMenu != nil {
-			processMenuItem(submenu, menuItem)
+			for _, menuItem := range menuItem.SubMenu.Items {
+				processMenuItem(submenu, menuItem)
+			}
 		}
 	}
 	mainMenu.Show()

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

@@ -0,0 +1,62 @@
+package windows
+
+import (
+	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/win32"
+	"github.com/wailsapp/wails/v2/pkg/options/windows"
+)
+
+func (w *Window) updateTheme() {
+
+	if win32.IsCurrentlyHighContrastMode() {
+		return
+	}
+
+	if !win32.SupportsThemes() {
+		return
+	}
+	// Only process if there's a theme change
+	isDarkMode := win32.IsCurrentlyDarkMode()
+	w.isDarkMode = isDarkMode
+
+	// Default use system theme
+	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 {
+			if isDarkMode {
+				println("1")
+				win32.SetTitleBarColour(w.Handle(), customTheme.DarkModeTitleBar)
+				win32.SetTitleTextColour(w.Handle(), customTheme.DarkModeTitleText)
+				win32.SetBorderColour(w.Handle(), customTheme.DarkModeBorder)
+			} else {
+				println("2")
+				win32.SetTitleBarColour(w.Handle(), customTheme.LightModeTitleBar)
+				win32.SetTitleTextColour(w.Handle(), customTheme.LightModeTitleText)
+				win32.SetBorderColour(w.Handle(), customTheme.LightModeBorder)
+			}
+		} else {
+			if isDarkMode {
+				win32.SetTitleBarColour(w.Handle(), customTheme.DarkModeTitleBarInactive)
+				win32.SetTitleTextColour(w.Handle(), customTheme.DarkModeTitleTextInactive)
+				win32.SetBorderColour(w.Handle(), customTheme.DarkModeBorderInactive)
+			} else {
+				win32.SetTitleBarColour(w.Handle(), customTheme.LightModeTitleBarInactive)
+				win32.SetTitleTextColour(w.Handle(), customTheme.LightModeTitleTextInactive)
+				win32.SetBorderColour(w.Handle(), customTheme.LightModeBorderInactive)
+			}
+		}
+	}
+}

v2/internal/frontend/desktop/windows/win32/consts.go

@@ -0,0 +1,27 @@
+package win32
+
+import (
+	"github.com/wailsapp/wails/v2/internal/system/operatingsystem"
+	"syscall"
+)
+
+type HRESULT int32
+type HANDLE uintptr
+
+var (
+	moduser32                = syscall.NewLazyDLL("user32.dll")
+	procSystemParametersInfo = moduser32.NewProc("SystemParametersInfoW")
+	procGetWindowLong        = moduser32.NewProc("GetWindowLongW")
+)
+var (
+	moddwmapi                        = syscall.NewLazyDLL("dwmapi.dll")
+	procDwmSetWindowAttribute        = moddwmapi.NewProc("DwmSetWindowAttribute")
+	procDwmExtendFrameIntoClientArea = moddwmapi.NewProc("DwmExtendFrameIntoClientArea")
+)
+var windowsVersion, _ = operatingsystem.GetWindowsVersionInfo()
+
+func IsWindowsVersionAtLeast(major, minor, buildNumber int) bool {
+	return windowsVersion.Major >= major &&
+		windowsVersion.Minor >= minor &&
+		windowsVersion.Build >= buildNumber
+}

v2/internal/frontend/desktop/windows/win32/theme.go

@@ -0,0 +1,92 @@
+package win32
+
+import (
+	"golang.org/x/sys/windows/registry"
+	"unsafe"
+)
+
+type DWMWINDOWATTRIBUTE int32
+
+const DwmwaUseImmersiveDarkModeBefore20h1 DWMWINDOWATTRIBUTE = 19
+const DwmwaUseImmersiveDarkMode DWMWINDOWATTRIBUTE = 20
+const DwmwaBorderColor DWMWINDOWATTRIBUTE = 34
+const DwmwaCaptionColor DWMWINDOWATTRIBUTE = 35
+const DwmwaTextColor DWMWINDOWATTRIBUTE = 36
+
+const SPI_GETHIGHCONTRAST = 0x0042
+const HCF_HIGHCONTRASTON = 0x00000001
+
+func dwmSetWindowAttribute(hwnd uintptr, dwAttribute DWMWINDOWATTRIBUTE, pvAttribute unsafe.Pointer, cbAttribute uintptr) {
+	ret, _, err := procDwmSetWindowAttribute.Call(
+		hwnd,
+		uintptr(dwAttribute),
+		uintptr(pvAttribute),
+		cbAttribute)
+	if ret != 0 {
+		_ = err
+		// println(err.Error())
+	}
+}
+
+func SupportsThemes() bool {
+	// We can't support Windows versions before 17763
+	return IsWindowsVersionAtLeast(10, 0, 17763)
+}
+
+func SupportsCustomThemes() bool {
+	return IsWindowsVersionAtLeast(10, 0, 17763)
+}
+
+func SetTheme(hwnd uintptr, useDarkMode bool) {
+	if IsWindowsVersionAtLeast(10, 0, 17763) {
+		attr := DwmwaUseImmersiveDarkModeBefore20h1
+		if IsWindowsVersionAtLeast(10, 0, 18985) {
+			attr = DwmwaUseImmersiveDarkMode
+		}
+		dwmSetWindowAttribute(hwnd, attr, unsafe.Pointer(&useDarkMode), unsafe.Sizeof(&useDarkMode))
+	}
+}
+
+func SetTitleBarColour(hwnd uintptr, titleBarColour int32) {
+	dwmSetWindowAttribute(hwnd, DwmwaCaptionColor, unsafe.Pointer(&titleBarColour), unsafe.Sizeof(titleBarColour))
+}
+
+func SetTitleTextColour(hwnd uintptr, titleTextColour int32) {
+	dwmSetWindowAttribute(hwnd, DwmwaTextColor, unsafe.Pointer(&titleTextColour), unsafe.Sizeof(titleTextColour))
+}
+
+func SetBorderColour(hwnd uintptr, titleBorderColour int32) {
+	dwmSetWindowAttribute(hwnd, DwmwaBorderColor, unsafe.Pointer(&titleBorderColour), unsafe.Sizeof(titleBorderColour))
+}
+
+func IsCurrentlyDarkMode() bool {
+	key, err := registry.OpenKey(registry.CURRENT_USER, `SOFTWARE\Microsoft\Windows\CurrentVersion\Themes\Personalize`, registry.QUERY_VALUE)
+	if err != nil {
+		return false
+	}
+	defer key.Close()
+
+	AppsUseLightTheme, _, err := key.GetIntegerValue("AppsUseLightTheme")
+	if err != nil {
+		return false
+	}
+
+	return AppsUseLightTheme == 0
+}
+
+type highContrast struct {
+	CbSize            uint32
+	DwFlags           uint32
+	LpszDefaultScheme *int16
+}
+
+func IsCurrentlyHighContrastMode() bool {
+	var result highContrast
+	result.CbSize = uint32(unsafe.Sizeof(result))
+	res, _, err := procSystemParametersInfo.Call(SPI_GETHIGHCONTRAST, uintptr(result.CbSize), uintptr(unsafe.Pointer(&result)), 0)
+	if res == 0 {
+		_ = err
+		return false
+	}
+	return result.DwFlags&HCF_HIGHCONTRASTON == HCF_HIGHCONTRASTON
+}

v2/internal/frontend/desktop/windows/win32/window.go

@@ -0,0 +1,56 @@
+package win32
+
+import (
+	"fmt"
+	"log"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	WS_MAXIMIZE = 0x01000000
+
+	GWL_STYLE = -16
+)
+
+// http://msdn.microsoft.com/en-us/library/windows/desktop/bb773244.aspx
+type MARGINS struct {
+	CxLeftWidth, CxRightWidth, CyTopHeight, CyBottomHeight int32
+}
+
+func ExtendFrameIntoClientArea(hwnd uintptr) {
+	// -1: Adds the default frame styling (aero shadow and e.g. rounded corners on Windows 11)
+	//     Also shows the caption buttons if transparent ant translucent but they don't work.
+	//  0: Adds the default frame styling but no aero shadow, does not show the caption buttons.
+	//  1: Adds the default frame styling (aero shadow and e.g. rounded corners on Windows 11) but no caption buttons
+	//     are shown if transparent ant translucent.
+	margins := &MARGINS{1, 1, 1, 1} // Only extend 1 pixel to have the default frame styling but no caption buttons
+	if err := dwmExtendFrameIntoClientArea(hwnd, margins); err != nil {
+		log.Fatal(fmt.Errorf("DwmExtendFrameIntoClientArea failed: %s", err))
+	}
+}
+
+func IsWindowMaximised(hwnd uintptr) bool {
+	style := uint32(getWindowLong(hwnd, GWL_STYLE))
+	return style&WS_MAXIMIZE != 0
+}
+
+func dwmExtendFrameIntoClientArea(hwnd uintptr, margins *MARGINS) error {
+	ret, _, _ := procDwmExtendFrameIntoClientArea.Call(
+		hwnd,
+		uintptr(unsafe.Pointer(margins)))
+
+	if ret != 0 {
+		return syscall.GetLastError()
+	}
+
+	return nil
+}
+
+func getWindowLong(hwnd uintptr, index int) int32 {
+	ret, _, _ := procGetWindowLong.Call(
+		hwnd,
+		uintptr(index))
+
+	return int32(ret)
+}

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

@@ -3,9 +3,8 @@
 package windows
 
 import (
-	"fmt"
+	"github.com/wailsapp/wails/v2/internal/frontend/desktop/windows/win32"
-	"log"
+	"github.com/wailsapp/wails/v2/internal/system/operatingsystem"
-	"syscall"
 	"unsafe"
 
 	"github.com/leaanthony/winc"
@@ -20,15 +19,20 @@ type Window struct {
 	applicationMenu                          *menu.Menu
 	notifyParentWindowPositionChanged        func() error
 	minWidth, minHeight, maxWidth, maxHeight int
+	versionInfo                              *operatingsystem.WindowsVersionInfo
+	isDarkMode                               bool
+	isActive                                 bool
 }
 
-func NewWindow(parent winc.Controller, appoptions *options.App) *Window {
+func NewWindow(parent winc.Controller, appoptions *options.App, versionInfo *operatingsystem.WindowsVersionInfo) *Window {
 	result := &Window{
 		frontendOptions: appoptions,
 		minHeight:       appoptions.MinHeight,
 		minWidth:        appoptions.MinWidth,
 		maxHeight:       appoptions.MaxHeight,
 		maxWidth:        appoptions.MaxWidth,
+		versionInfo:     versionInfo,
+		isActive:        true,
 	}
 	result.SetIsForm(true)
 
@@ -46,7 +50,8 @@ func NewWindow(parent winc.Controller, appoptions *options.App) *Window {
 	var dwStyle = w32.WS_OVERLAPPEDWINDOW
 
 	winc.RegClassOnlyOnce("wailsWindow")
-	result.SetHandle(winc.CreateWindow("wailsWindow", parent, uint(exStyle), uint(dwStyle)))
+	handle := winc.CreateWindow("wailsWindow", parent, uint(exStyle), uint(dwStyle))
+	result.SetHandle(handle)
 	winc.RegMsgHandler(result)
 	result.SetParent(parent)
 
@@ -69,6 +74,8 @@ func NewWindow(parent winc.Controller, appoptions *options.App) *Window {
 		result.SetMaxSize(appoptions.MaxWidth, appoptions.MaxHeight)
 	}
 
+	result.updateTheme()
+
 	if appoptions.Windows != nil {
 		if appoptions.Windows.WindowIsTranslucent {
 			result.SetTranslucentBackground()
@@ -125,12 +132,26 @@ func (w *Window) SetMaxSize(maxWidth int, maxHeight int) {
 func (w *Window) WndProc(msg uint32, wparam, lparam uintptr) uintptr {
 
 	switch msg {
+	case w32.WM_SETTINGCHANGE:
+		settingChanged := w32.UTF16PtrToString((*uint16)(unsafe.Pointer(lparam)))
+		if settingChanged == "ImmersiveColorSet" {
+			w.updateTheme()
+		}
+		return 0
 	case w32.WM_NCLBUTTONDOWN:
 		w32.SetFocus(w.Handle())
 	case w32.WM_MOVE, w32.WM_MOVING:
 		if w.notifyParentWindowPositionChanged != nil {
 			w.notifyParentWindowPositionChanged()
 		}
+	case w32.WM_ACTIVATE:
+		if int(wparam) == w32.WA_INACTIVE {
+			w.isActive = false
+			w.updateTheme()
+		} else {
+			w.isActive = true
+			w.updateTheme()
+		}
 
 	// TODO move WM_DPICHANGED handling into winc
 	case 0x02E0: //w32.WM_DPICHANGED
@@ -152,15 +173,7 @@ func (w *Window) WndProc(msg uint32, wparam, lparam uintptr) uintptr {
 			// As a result we have hidden the titlebar but still have the default window frame styling.
 			// See: https://docs.microsoft.com/en-us/windows/win32/api/dwmapi/nf-dwmapi-dwmextendframeintoclientarea#remarks
 			if winoptions := w.frontendOptions.Windows; winoptions == nil || !winoptions.DisableFramelessWindowDecorations {
-				// -1: Adds the default frame styling (aero shadow and e.g. rounded corners on Windows 11)
+				win32.ExtendFrameIntoClientArea(w.Handle())
-				//     Also shows the caption buttons if transparent ant translucent but they don't work.
-				//  0: Adds the default frame styling but no aero shadow, does not show the caption buttons.
-				//  1: Adds the default frame styling (aero shadow and e.g. rounded corners on Windows 11) but no caption buttons
-				//     are shown if transparent ant translucent.
-				margins := w32.MARGINS{1, 1, 1, 1} // Only extend 1 pixel to have the default frame styling but no caption buttons
-				if err := dwmExtendFrameIntoClientArea(w.Handle(), margins); err != nil {
-					log.Fatal(fmt.Errorf("DwmExtendFrameIntoClientArea failed: %s", err))
-				}
 			}
 		case w32.WM_NCCALCSIZE:
 			// Disable the standard frame by allowing the client area to take the full
@@ -208,25 +221,6 @@ func (w *Window) WndProc(msg uint32, wparam, lparam uintptr) uintptr {
 }
 
 func (w *Window) IsMaximised() bool {
-	style := uint32(w32.GetWindowLong(w.Handle(), w32.GWL_STYLE))
+	return win32.IsWindowMaximised(w.Handle())
-	return style&w32.WS_MAXIMIZE != 0
+
-}
-
-// TODO this should be put into the winc if we are happy with this solution.
-var (
-	modkernel32 = syscall.NewLazyDLL("dwmapi.dll")
-
-	procDwmExtendFrameIntoClientArea = modkernel32.NewProc("DwmExtendFrameIntoClientArea")
-)
-
-func dwmExtendFrameIntoClientArea(hwnd w32.HWND, margins w32.MARGINS) error {
-	ret, _, _ := procDwmExtendFrameIntoClientArea.Call(
-		uintptr(hwnd),
-		uintptr(unsafe.Pointer(&margins)))
-
-	if ret != 0 {
-		return syscall.GetLastError()
-	}
-
-	return nil
 }

v2/internal/system/operatingsystem/version_windows.go

@@ -0,0 +1,59 @@
+package operatingsystem
+
+import (
+	"golang.org/x/sys/windows/registry"
+	"strconv"
+)
+
+type WindowsVersionInfo struct {
+	Major          int
+	Minor          int
+	Build          int
+	DisplayVersion string
+}
+
+func (w *WindowsVersionInfo) IsWindowsVersionAtLeast(major, minor, buildNumber int) bool {
+	return w.Major >= major && w.Minor >= minor && w.Build >= buildNumber
+}
+
+func GetWindowsVersionInfo() (*WindowsVersionInfo, error) {
+	key, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\Windows NT\CurrentVersion`, registry.QUERY_VALUE)
+	if err != nil {
+		return nil, err
+	}
+
+	return &WindowsVersionInfo{
+		Major:          regDWORDKeyAsInt(key, "CurrentMajorVersionNumber"),
+		Minor:          regDWORDKeyAsInt(key, "CurrentMinorVersionNumber"),
+		Build:          regStringKeyAsInt(key, "CurrentBuildNumber"),
+		DisplayVersion: regKeyAsString(key, "DisplayVersion"),
+	}, nil
+}
+
+func regDWORDKeyAsInt(key registry.Key, name string) int {
+	result, _, err := key.GetIntegerValue(name)
+	if err != nil {
+		return -1
+	}
+	return int(result)
+}
+
+func regStringKeyAsInt(key registry.Key, name string) int {
+	resultStr, _, err := key.GetStringValue(name)
+	if err != nil {
+		return -1
+	}
+	result, err := strconv.Atoi(resultStr)
+	if err != nil {
+		return -1
+	}
+	return result
+}
+
+func regKeyAsString(key registry.Key, name string) string {
+	resultStr, _, err := key.GetStringValue(name)
+	if err != nil {
+		return ""
+	}
+	return resultStr
+}

v2/pkg/options/windows/windows.go

@@ -1,5 +1,40 @@
 package windows
 
+type Theme int
+
+const (
+	// SystemDefault will use whatever the system theme is. The application will follow system theme changes.
+	SystemDefault Theme = 0
+	// Dark Mode
+	Dark Theme = 1
+	// Light Mode
+	Light Theme = 2
+)
+
+func RGB(r, g, b uint8) int32 {
+	var col = int32(b)
+	col = col<<8 | int32(g)
+	col = col<<8 | int32(r)
+	return col
+}
+
+// ThemeSettings contains optional colours to use.
+// They may be set using the hex values: 0x00BBGGRR
+type ThemeSettings struct {
+	DarkModeTitleBar           int32
+	DarkModeTitleBarInactive   int32
+	DarkModeTitleText          int32
+	DarkModeTitleTextInactive  int32
+	DarkModeBorder             int32
+	DarkModeBorderInactive     int32
+	LightModeTitleBar          int32
+	LightModeTitleBarInactive  int32
+	LightModeTitleText         int32
+	LightModeTitleTextInactive int32
+	LightModeBorder            int32
+	LightModeBorderInactive    int32
+}
+
 // Options are options specific to Windows
 type Options struct {
 	WebviewIsTransparent bool
@@ -13,4 +48,10 @@ type Options struct {
 	// Path where the WebView2 stores the user data. If empty %APPDATA%\[BinaryName.exe] will be used.
 	// If the path is not valid, a messagebox will be displayed with the error and the app will exit with error code.
 	WebviewUserDataPath string
+
+	// Dark/Light or System Default Theme
+	Theme Theme
+
+	// Custom settings for dark/light mode
+	CustomTheme *ThemeSettings
 }

website/docs/reference/options.mdx

@@ -47,6 +47,15 @@ func main() {
             DisableWindowIcon:                 false,
             DisableFramelessWindowDecorations: false,
             WebviewUserDataPath:               "",
+            Theme:                             windows.SystemDefault,
+            CustomTheme: &windows.ThemeSettings{
+                DarkModeTitleBar:   windows.RGB(20, 20, 20),
+                DarkModeTitleText:  windows.RGB(200, 200, 200),
+                DarkModeBorder:     windows.RGB(20, 0, 20),
+                LightModeTitleBar:  windows.RGB(200, 200, 200),
+                LightModeTitleText: windows.RGB(20, 20, 20),
+                LightModeBorder:    windows.RGB(200, 200, 200),
+            },
         },
         Mac: &mac.Options{
             TitleBar: &mac.TitleBar{
@@ -375,6 +384,78 @@ Type: string
 
 This defines the path where the WebView2 stores the user data. If empty `%APPDATA%\[BinaryName.exe]` will be used.
 
+### Theme
+
+Name: Theme
+
+Type: `windows.Theme`
+
+Minimum Windows Version: Windows 10 2004/20H1
+
+This defines the theme that the application should use:
+
+| Value           | Description |
+| --------------- | ----------- |
+| SystemDefault   | *Default*. The theme will be based on the system default. If the user changes their theme, the application will update to use the new setting |
+| Dark            | The application will use a dark theme exclusively |
+| Light           | The application will use a light theme exclusively |
+
+
+### CustomTheme
+
+Name: CustomTheme
+
+Type: `windows.CustomTheme`
+
+Minimum Windows Version: Windows 10/11 2009/21H2 Build 22000
+
+Allows you to specify custom colours for TitleBar, TitleText and Border for both light and dark mode, as well as
+when the window is active or inactive.
+
+#### CustomTheme
+
+The CustomTheme struct uses `int32` to specify the colour values. These are in the standard(!) Windows format of:
+`0x00BBGGAA`. A helper function is provided to do RGB conversions into this format: `windows.RGB(r,g,b uint8)`.
+
+NOTE: Any value not provided will default to black.
+
+```go
+type ThemeSettings struct {
+	DarkModeTitleBar           int32
+	DarkModeTitleBarInactive   int32
+	DarkModeTitleText          int32
+	DarkModeTitleTextInactive  int32
+	DarkModeBorder             int32
+	DarkModeBorderInactive     int32
+	LightModeTitleBar          int32
+	LightModeTitleBarInactive  int32
+	LightModeTitleText         int32
+	LightModeTitleTextInactive int32
+	LightModeBorder            int32
+	LightModeBorderInactive    int32
+}
+```
+
+Example:
+```go
+    CustomTheme: &windows.ThemeSettings{
+        // Theme to use when window is active
+        DarkModeTitleBar:   windows.RGB(255, 0, 0),   // Red
+        DarkModeTitleText:  windows.RGB(0, 255, 0),   // Green
+        DarkModeBorder:     windows.RGB(0, 0, 255),   // Blue
+        LightModeTitleBar:  windows.RGB(200, 200, 200),
+        LightModeTitleText: windows.RGB(20, 20, 20),
+        LightModeBorder:    windows.RGB(200, 200, 200),
+        // Theme to use when window is inactive
+        DarkModeTitleBarInactive:   windows.RGB(128, 0, 0),
+        DarkModeTitleTextInactive:  windows.RGB(0, 128, 0),
+        DarkModeBorderInactive:     windows.RGB(0, 0, 128),
+        LightModeTitleBarInactive:  windows.RGB(100, 100, 100),
+        LightModeTitleTextInactive: windows.RGB(10, 10, 10),
+        LightModeBorderInactive:    windows.RGB(100, 100, 100),
+    },
+```
+
 ## Mac Specific Options
 
 ### TitleBar