Add a windows 10 workaround to force dark mode

cmd/fyne/internal/commands/package.go

@@ -3,6 +3,7 @@ package commands
 import (
 	"flag"
 	"fmt"
+
 	// import image encodings
 	_ "image/jpeg"
 	_ "image/png"

internal/driver/glfw/window.go

@@ -1,6 +1,5 @@
 package glfw
 
-import "C"
 import (
 	"bytes"
 	"context"
@@ -10,14 +9,15 @@ import (
 	"sync"
 	"time"
 
+	"github.com/go-gl/glfw/v3.3/glfw"
+
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/driver/desktop"
 	"fyne.io/fyne/v2/internal"
 	"fyne.io/fyne/v2/internal/cache"
 	"fyne.io/fyne/v2/internal/driver"
 	"fyne.io/fyne/v2/internal/painter/gl"
-
-	"github.com/go-gl/glfw/v3.3/glfw"
+	"fyne.io/fyne/v2/theme"
 )
 
 const (
@@ -1449,6 +1449,8 @@ func (w *window) create() {
 	})
 
 	runOnMain(func() {
+		w.setDarkMode(fyne.CurrentApp().Settings().ThemeVariant() == theme.VariantDark)
+
 		win := w.view()
 		win.SetCloseCallback(w.closed)
 		win.SetPosCallback(w.moved)
@@ -1533,3 +1535,17 @@ func isKeyModifier(keyName fyne.KeyName) bool {
 		keyName == desktop.KeyAltLeft || keyName == desktop.KeyAltRight ||
 		keyName == desktop.KeySuperLeft || keyName == desktop.KeySuperRight
 }
+
+//lint:ignore U1000 This is fine, just a helper function for some platforms
+func standardResize(w *window, size fyne.Size) {
+	d, ok := fyne.CurrentApp().Driver().(*gLDriver)
+	if !ok { // don't wait to redraw in this way if we are running on test
+		w.canvas.Resize(size)
+		return
+	}
+
+	runOnDraw(w, func() {
+		w.canvas.Resize(size)
+		d.repaintWindow(w)
+	})
+}

internal/driver/glfw/window_linux.go

@@ -6,3 +6,6 @@ func (w *window) platformResize(canvasSize fyne.Size) {
 	w.canvas.Resize(canvasSize)
 	w.canvas.Refresh(w.canvas.content)
 }
+
+func (w *window) setDarkMode(dark bool) {
+}

internal/driver/glfw/window_other.go

@@ -1,18 +1,12 @@
-// +build !linux
+// +build !linux,!windows
 
 package glfw
 
 import "fyne.io/fyne/v2"
 
 func (w *window) platformResize(canvasSize fyne.Size) {
-	d, ok := fyne.CurrentApp().Driver().(*gLDriver)
-	if !ok { // don't wait to redraw in this way if we are running on test
-		w.canvas.Resize(canvasSize)
-		return
-	}
+	standardResize(w, canvasSize)
+}
 
-	runOnDraw(w, func() {
-		w.canvas.Resize(canvasSize)
-		d.repaintWindow(w)
-	})
+func (w *window) setDarkMode(dark bool) {
 }

internal/driver/glfw/window_windows.go

@@ -0,0 +1,30 @@
+package glfw
+
+import (
+	"runtime"
+	"syscall"
+	"unsafe"
+
+	"fyne.io/fyne/v2"
+)
+
+func (w *window) platformResize(canvasSize fyne.Size) {
+	standardResize(w, canvasSize)
+}
+
+func (w *window) setDarkMode(dark bool) {
+	if runtime.GOOS == "windows" {
+		hwnd := w.view().GetWin32Window()
+
+		dwm := syscall.NewLazyDLL("dwmapi.dll")
+		setAtt := dwm.NewProc("DwmSetWindowAttribute")
+		ret, _, err := setAtt.Call(uintptr(unsafe.Pointer(hwnd)), // window handle
+			20,                             // DWMWA_USE_IMMERSIVE_DARK_MODE
+			uintptr(unsafe.Pointer(&dark)), // on or off
+			8)                              // sizeof(darkMode)
+
+		if ret != 0 { // err is always non-nil, we check return value
+			fyne.LogError("Failed to set dark mode", err)
+		}
+	}
+}