Add -reload-theme CLI flag to re-apply the current theme file (#860)

* Add -reload-theme CLI flag to re-apply theme via IPC

Sends a reload-theme IPC message to a running instance, causing it to
call fyne.CurrentApp().Settings().SetTheme(m.theme). Follows the same
callback pattern as -show (OnReactivate) and quit (OnExit).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* actually re-read theme file

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app.go

@@ -60,6 +60,7 @@ type App struct {
 	// UI callbacks to be set in main
 	OnReactivate func()
 	OnExit       func()
+	OnReloadTheme func()
 
 	appName        string
 	displayAppName string
@@ -227,7 +228,8 @@ func StartupApp(appName, displayAppName, appVersion, appVersionTag, latestReleas
 				ipcRatingHandler,
 				a.ServerManager,
 				a.callOnReactivate,
-				func() { _ = a.callOnExit() })
+				func() { _ = a.callOnExit() },
+				a.callOnReloadTheme)
 			go a.ipcServer.Serve(listener)
 		} else {
 			log.Printf("error starting IPC server: %s", err.Error())
@@ -336,6 +338,12 @@ func (a *App) callOnReactivate() {
 	}
 }
 
+func (a *App) callOnReloadTheme() {
+	if a.OnReloadTheme != nil {
+		a.OnReloadTheme()
+	}
+}
+
 func (a *App) callOnExit() error {
 	if a.OnExit == nil {
 		return errors.New("no quit handler registered")
@@ -658,6 +666,8 @@ func (a *App) checkFlagsAndSendIPCMsg(cli *ipc.Client) error {
 		return cli.PauseAfterCurrent()
 	case *FlagShow:
 		return cli.Show()
+	case *FlagReloadTheme:
+		return cli.ReloadTheme()
 	case VolumeCLIArg >= 0:
 		return cli.SetVolume(VolumeCLIArg)
 	case VolumePctCLIArg != 0:

backend/cmdlineoptions.go

@@ -32,6 +32,7 @@ var (
 	FlagPauseAfterCurrent = flag.Bool("pause-after-current", false, "pause playback after current track")
 	FlagStartMinimized    = flag.Bool("start-minimized", false, "start app minimized")
 	FlagShow              = flag.Bool("show", false, "show minimized app")
+	FlagReloadTheme       = flag.Bool("reload-theme", false, "reload the current theme")
 	FlagShuffle           = flag.Bool("shuffle", false, "shuffle the tracklist (to be used with either -play-album-by-id or -play-playlist-by-id)")
 	FlagVersion           = flag.Bool("version", false, "print app version and exit")
 	FlagHelp              = flag.Bool("help", false, "print command line options and exit")

backend/ipc/api.go

@@ -26,6 +26,7 @@ const (
 	VolumePath            = "/volume"            // ?v=<vol>
 	VolumeAdjustPath      = "/volume/adjust"     // ?pct=<+/- percentage>
 	ShowPath              = "/window/show"
+	ReloadThemePath       = "/window/reload-theme"
 	QuitPath              = "/window/quit"
 	RateCurrentTrackPath  = "/current_track/rate" // ?r=<rating 0-5>
 )

backend/ipc/client.go

@@ -128,6 +128,11 @@ func (c *Client) Show() error {
 	return err
 }
 
+func (c *Client) ReloadTheme() error {
+	_, err := c.sendRequest(ReloadThemePath)
+	return err
+}
+
 func (c *Client) Quit() error {
 	_, err := c.sendRequest(QuitPath)
 	return err

backend/ipc/server.go

@@ -47,10 +47,11 @@ type serverImpl struct {
 	sm              ServerManager
 	showFn          func()
 	quitFn          func()
+	reloadThemeFn   func()
 }
 
-func NewServer(pbHandler PlaybackHandler, rateFn func(int), sm ServerManager, showFn, quitFn func()) IPCServer {
-	s := &serverImpl{pbHandler: pbHandler, rateFn: rateFn, sm: sm, showFn: showFn, quitFn: quitFn}
+func NewServer(pbHandler PlaybackHandler, rateFn func(int), sm ServerManager, showFn, quitFn, reloadThemeFn func()) IPCServer {
+	s := &serverImpl{pbHandler: pbHandler, rateFn: rateFn, sm: sm, showFn: showFn, quitFn: quitFn, reloadThemeFn: reloadThemeFn}
 	s.server = &http.Server{
 		Handler: s.createHandler(),
 	}
@@ -77,6 +78,7 @@ func (s *serverImpl) createHandler() http.Handler {
 	m.HandleFunc(ShowPath, s.makeSimpleEndpointHandler(func() {
 		s.showFn()
 	}))
+	m.HandleFunc(ReloadThemePath, s.makeSimpleEndpointHandler(s.reloadThemeFn))
 	m.HandleFunc(QuitPath, s.makeSimpleEndpointHandler(func() {
 		s.quitFn()
 	}))

main.go

@@ -110,6 +110,7 @@ func main() {
 	mainWindow.Window.SetMaster()
 	myApp.OnReactivate = util.FyneDoFunc(mainWindow.Show)
 	myApp.OnExit = util.FyneDoFunc(mainWindow.Quit)
+	myApp.OnReloadTheme = util.FyneDoFunc(mainWindow.ReloadTheme)
 
 	if runtime.GOOS == "windows" {
 		windowStartupTasks := sync.OnceFunc(func() {

ui/mainwindow.go

@@ -273,6 +273,11 @@ func (m *MainWindow) setInitialSize() {
 	m.Window.Resize(m.DesiredSize())
 }
 
+func (m *MainWindow) ReloadTheme() {
+	m.theme.ReloadThemeFile()
+	fyne.CurrentApp().Settings().SetTheme(m.theme)
+}
+
 func (m *MainWindow) StartupPage() controller.Route {
 	switch m.App.Config.Application.StartupPage {
 	case "Artists":

ui/theme/theme.go

@@ -110,6 +110,11 @@ func NewMyTheme(config *backend.ThemeConfig, themeFileDir string) *MyTheme {
 	return m
 }
 
+// ReloadThemeFile reloads the currently loaded theme file.
+func (m *MyTheme) ReloadThemeFile() {
+	m.loadedThemeFile = nil
+}
+
 func (m *MyTheme) Color(name fyne.ThemeColorName, defVariant fyne.ThemeVariant) color.Color {
 	// load theme file if necessary
 	if m.loadedThemeFile == nil || m.config.ThemeFile != m.loadedThemeFilename {