add cmdline flags and some fixes to the IPC layer

backend/cmdlineoptions.go

@@ -0,0 +1,41 @@
+package backend
+
+import (
+	"flag"
+	"strconv"
+)
+
+var (
+	VolumeCLIArg int     = -1
+	SeekToCLIArg float64 = -1
+
+	FlagPlay      = flag.Bool("play", false, "unpause or begin playback")
+	FlagPause     = flag.Bool("pause", false, "pause playback")
+	FlagPlayPause = flag.Bool("play-pause", false, "toggle play/pause state")
+	FlagPrevious  = flag.Bool("previous", false, "seek to previous track or beginning of current")
+	FlagNext      = flag.Bool("next", false, "seek to next track")
+	FlagVersion   = flag.Bool("version", false, "print app version and exit")
+	FlagHelp      = flag.Bool("help", false, "print command line options and exit")
+)
+
+func init() {
+	flag.Func("volume", "sets the playback volume (0-100)", func(s string) error {
+		v, err := strconv.Atoi(s)
+		VolumeCLIArg = v
+		return err
+	})
+
+	flag.Func("seek-to", "seeks to the given position in seconds in the current file (0.0 - <trackDur>)", func(s string) error {
+		v, err := strconv.ParseFloat(s, 64)
+		SeekToCLIArg = v
+		return err
+	})
+}
+
+func HaveCommandLineOptions() bool {
+	visitedAny := false
+	flag.Visit(func(*flag.Flag) {
+		visitedAny = true
+	})
+	return visitedAny
+}