add Windows taskbar control buttons (TODO: icons)

backend/windows/smtc_unsupported.go

@@ -0,0 +1,55 @@
+//go:build !windows
+
+package windows
+
+import "errors"
+
+type SMTCPlaybackState int
+type SMTCButton int
+
+const (
+	// constants from smtc.h in github.com/supersonic-app/smtc-dll
+	SMTCPlaybackStateStopped SMTCPlaybackState = 2
+	SMTCPlaybackStatePlaying SMTCPlaybackState = 3
+	SMTCPlaybackStatePaused  SMTCPlaybackState = 4
+
+	SMTCButtonPlay     SMTCButton = 0
+	SMTCButtonPause    SMTCButton = 1
+	SMTCButtonStop     SMTCButton = 2
+	SMTCButtonPrevious SMTCButton = 4
+	SMTCButtonNext     SMTCButton = 5
+)
+
+type SMTC struct{}
+
+var smtcUnsupportedErr = errors.New("SMTC is not supported on this platformo")
+
+func InitSMTCForWindow(hwnd uintptr) (*SMTC, error) {
+	return nil, smtcUnsupportedErr
+}
+
+func (s *SMTC) SetEnabled(enabled bool) error {
+	return smtcUnsupportedErr
+}
+
+func (s *SMTC) SetThumbnail(filepath string) error {
+	return smtcUnsupportedErr
+}
+
+func (s *SMTC) OnButtonPressed(func(SMTCButton)) {}
+
+func (s *SMTC) OnSeek(f func(millis int)) {}
+
+func (s *SMTC) Shutdown() {}
+
+func (s *SMTC) UpdatePlaybackState(state SMTCPlaybackState) error {
+	return smtcUnsupportedErr
+}
+
+func (s *SMTC) UpdateMetadata(title, artist string) error {
+	return smtcUnsupportedErr
+}
+
+func (s *SMTC) UpdatePosition(positionMillis, durationMillis int) error {
+	return smtcUnsupportedErr
+}