Fix #522: add -volume-adjust-pct CLI arg

backend/ipc/api.go

@@ -3,18 +3,19 @@ package ipc
 import "fmt"
 
 const (
-	PingPath      = "/ping"
-	PlayPath      = "/transport/play"
-	PlayPausePath = "/transport/playpause"
-	PausePath     = "/transport/pause"
-	StopPath      = "/transport/stop"
-	PreviousPath  = "/transport/previous"
-	NextPath      = "/transport/next"
-	TimePosPath   = "/transport/timepos" // ?s=<seconds>
-	SeekByPath    = "/transport/seek-by" // ?s=<+/- seconds>
-	VolumePath    = "/volume"            // ?v=<vol>
-	ShowPath      = "/window/show"
-	QuitPath      = "/window/quit"
+	PingPath         = "/ping"
+	PlayPath         = "/transport/play"
+	PlayPausePath    = "/transport/playpause"
+	PausePath        = "/transport/pause"
+	StopPath         = "/transport/stop"
+	PreviousPath     = "/transport/previous"
+	NextPath         = "/transport/next"
+	TimePosPath      = "/transport/timepos" // ?s=<seconds>
+	SeekByPath       = "/transport/seek-by" // ?s=<+/- seconds>
+	VolumePath       = "/volume"            // ?v=<vol>
+	VolumeAdjustPath = "/volume/adjust"     // ?pct=<+/- percentage>
+	ShowPath         = "/window/show"
+	QuitPath         = "/window/quit"
 )
 
 type Response struct {
@@ -25,6 +26,10 @@ func SetVolumePath(vol int) string {
 	return fmt.Sprintf("%s?v=%d", VolumePath, vol)
 }
 
+func AdjustVolumePctPath(pct float64) string {
+	return fmt.Sprintf("%s?pct=%0.2f", VolumeAdjustPath, pct)
+}
+
 func SeekToSecondsPath(secs float64) string {
 	return fmt.Sprintf("%s?s=%0.2f", TimePosPath, secs)
 }

backend/ipc/client.go

@@ -68,6 +68,10 @@ func (c *Client) SetVolume(vol int) error {
 	return c.sendRequest(SetVolumePath(vol))
 }
 
+func (c *Client) AdjustVolumePct(pct float64) error {
+	return c.sendRequest(AdjustVolumePctPath(pct))
+}
+
 func (c *Client) Show() error {
 	return c.sendRequest(ShowPath)
 }

backend/ipc/server.go

@@ -70,8 +70,8 @@ func (s *serverImpl) createHandler() http.Handler {
 	m.HandleFunc(StopPath, s.makeSimpleEndpointHandler(s.pbHandler.Stop))
 	m.HandleFunc(PreviousPath, s.makeSimpleEndpointHandler(s.pbHandler.SeekBackOrPrevious))
 	m.HandleFunc(NextPath, s.makeSimpleEndpointHandler(s.pbHandler.SeekNext))
-	m.HandleFunc(TimePosPath, s.makeFloatEndpointHandler(s.pbHandler.SeekSeconds, "s"))
-	m.HandleFunc(SeekByPath, s.makeFloatEndpointHandler(s.pbHandler.SeekBySeconds, "s"))
+	m.HandleFunc(TimePosPath, s.makeFloatEndpointHandler("s", s.pbHandler.SeekSeconds))
+	m.HandleFunc(SeekByPath, s.makeFloatEndpointHandler("s", s.pbHandler.SeekBySeconds))
 	m.HandleFunc(VolumePath, func(w http.ResponseWriter, r *http.Request) {
 		v := r.URL.Query().Get("v")
 		if vol, err := strconv.Atoi(v); err == nil {
@@ -81,6 +81,11 @@ func (s *serverImpl) createHandler() http.Handler {
 			s.writeErr(w, err)
 		}
 	})
+	m.HandleFunc(VolumeAdjustPath, s.makeFloatEndpointHandler("pct", func(pct float64) {
+		vol := s.pbHandler.Volume()
+		vol = vol + int(float64(vol)*(pct/100))
+		s.pbHandler.SetVolume(vol) // will clamp to range for us
+	}))
 	return m
 }
 
@@ -91,7 +96,7 @@ func (s *serverImpl) makeSimpleEndpointHandler(f func()) func(http.ResponseWrite
 	}
 }
 
-func (s *serverImpl) makeFloatEndpointHandler(f func(float64), queryParam string) func(http.ResponseWriter, *http.Request) {
+func (s *serverImpl) makeFloatEndpointHandler(queryParam string, f func(float64)) func(http.ResponseWriter, *http.Request) {
 	return func(w http.ResponseWriter, r *http.Request) {
 		v := r.URL.Query().Get(queryParam)
 		if val, err := strconv.ParseFloat(v, 64); err == nil {