initial implementation of Windows SMTC integration

backend/smtc_unsupported.go

@@ -0,0 +1,32 @@
+//go:build !windows
+
+package backend
+
+import "errors"
+
+type SMTCPlaybackState int
+
+const (
+	SMTCPlaybackStateStopped SMTCPlaybackState = 0
+	SMTCPlaybackStatePlaying SMTCPlaybackState = 1
+	SMTCPlaybackStatePaused  SMTCPlaybackState = 2
+)
+
+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) UpdatePlaybackState(state SMTCPlaybackState) error {
+	return smtcUnsupportedErr
+}
+
+func (s *SMTC) UpdateMetadata(title, artist string) error {
+	return smtcUnsupportedErr
+}
+
+func (s *SMTC) Shutdown() {
+}