add Windows taskbar control buttons (TODO: icons)

backend/windows/smtc.go

@@ -0,0 +1,207 @@
+//go:build windows
+
+package windows
+
+/*
+#cgo CFLAGS: -I .
+void btn_callback_cgo(int in);
+void seek_callback_cgo(int in);
+*/
+import "C"
+
+import (
+	"errors"
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+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 {
+	dll *windows.DLL
+
+	onButtonPressed func(SMTCButton)
+	onSeek          func(int)
+}
+
+var smtcInstance *SMTC
+
+func InitSMTCForWindow(hwnd uintptr) (*SMTC, error) {
+	if maj, _, _ := windows.RtlGetNtVersionNumbers(); maj < 10 {
+		return nil, errors.New("SMTC is not supported on Windows versions < 10")
+	}
+
+	dll, err := windows.LoadDLL("smtc.dll")
+	if err != nil {
+		return nil, err
+	}
+
+	proc, err := dll.FindProc("InitializeForWindow")
+	if err != nil {
+		return nil, err
+	}
+
+	hr, _, _ := proc.Call(hwnd, uintptr(unsafe.Pointer(C.btn_callback_cgo)), uintptr(unsafe.Pointer(C.seek_callback_cgo)))
+	if hr < 0 {
+		return nil, fmt.Errorf("InitializeForWindow failed with HRESULT=%d", hr)
+	}
+
+	smtcInstance = &SMTC{dll: dll}
+	return smtcInstance, nil
+}
+
+func (s *SMTC) OnButtonPressed(f func(SMTCButton)) {
+	s.onButtonPressed = f
+}
+
+func (s *SMTC) OnSeek(f func(millis int)) {
+	s.onSeek = f
+}
+
+func (s *SMTC) Shutdown() {
+	if s.dll == nil {
+		return
+	}
+	proc, err := s.dll.FindProc("Destroy")
+	if err == nil {
+		proc.Call()
+	}
+
+	s.dll.Release()
+	s.dll = nil
+	smtcInstance = nil
+}
+
+func (s *SMTC) UpdatePlaybackState(state SMTCPlaybackState) error {
+	if s.dll == nil {
+		return errors.New("SMTC DLL not available")
+	}
+
+	proc, err := s.dll.FindProc("SetPlaybackState")
+	if err != nil {
+		return err
+	}
+
+	if hr, _, _ := proc.Call(uintptr(state)); hr < 0 {
+		return fmt.Errorf("SetPlaybackState failed with HRESULT=%d", hr)
+	}
+	return nil
+}
+
+func (s *SMTC) UpdateMetadata(title, artist string) error {
+	if s.dll == nil {
+		return errors.New("SMTC DLL not available")
+	}
+
+	utfTitle, err := windows.UTF16PtrFromString(title)
+	if err != nil {
+		return err
+	}
+
+	utfArtist, err := windows.UTF16PtrFromString(artist)
+	if err != nil {
+		return err
+	}
+
+	proc, err := s.dll.FindProc("SetMetadata")
+	if err != nil {
+		return err
+	}
+
+	hr, _, _ := proc.Call(uintptr(unsafe.Pointer(utfTitle)), uintptr(unsafe.Pointer(utfArtist)))
+	if hr < 0 {
+		return fmt.Errorf("SetMetadata failed with HRESULT=%d", hr)
+	}
+	return nil
+}
+
+func (s *SMTC) UpdatePosition(positionMillis, durationMillis int) error {
+	if s.dll == nil {
+		return errors.New("SMTC DLL not available")
+	}
+
+	proc, err := s.dll.FindProc("SetPosition")
+	if err != nil {
+		return err
+	}
+
+	hr, _, _ := proc.Call(uintptr(positionMillis), uintptr(durationMillis))
+	if hr < 0 {
+		return fmt.Errorf("SetPosition failed with HRESULT=%d", hr)
+	}
+	return nil
+}
+
+func (s *SMTC) SetThumbnail(filepath string) error {
+	if s.dll == nil {
+		return errors.New("SMTC DLL not available")
+	}
+
+	proc, err := s.dll.FindProc("SetThumbnailPath")
+	if err != nil {
+		return err
+	}
+
+	utfPath, err := windows.UTF16PtrFromString(filepath)
+	if err != nil {
+		return err
+	}
+
+	hr, _, _ := proc.Call(uintptr(unsafe.Pointer(utfPath)))
+	if hr < 0 {
+		return fmt.Errorf("SetThumbnailPath failed with HRESULT=%d", hr)
+	}
+	return nil
+}
+
+func (s *SMTC) SetEnabled(enabled bool) error {
+	if s.dll == nil {
+		return errors.New("SMTC DLL not available")
+	}
+
+	proc, err := s.dll.FindProc("SetEnabled")
+	if err != nil {
+		return err
+	}
+
+	var arg uintptr = 0
+	if enabled {
+		arg = 1
+	}
+
+	hr, _, _ := proc.Call(arg)
+	if hr < 0 {
+		return fmt.Errorf("SetEnabled failed with HRESULT=%d", hr)
+	}
+	return nil
+}
+
+//export btnCallback
+func btnCallback(in int) {
+	if smtcInstance != nil && smtcInstance.onButtonPressed != nil {
+		smtcInstance.onButtonPressed(SMTCButton(in))
+	}
+}
+
+//export seekCallback
+func seekCallback(millis int) {
+	if smtcInstance != nil && smtcInstance.onSeek != nil {
+		smtcInstance.onSeek(millis)
+	}
+}