add watching bus ability

examples/device_provider/main.go

@@ -38,6 +38,31 @@ func runPipeline(loop *glib.MainLoop) error {
 	// 	os.Exit(2)
 	// }
 
+	fmt.Println("Getting device provider bus")
+	bus := provider.GetBus()
+	fmt.Println("Got device provider bus", bus)
+
+	bus.AddWatch(func(msg *gst.Message) bool {
+		switch msg.Type() {
+		case gst.MessageDeviceAdded:
+			message := msg.ParseDeviceAdded().GetDisplayName()
+			fmt.Println("Added: ", message)
+		case gst.MessageDeviceRemoved:
+			message := msg.ParseDeviceRemoved().GetDisplayName()
+			fmt.Println("Removed: ", message)
+		default:
+			// All messages implement a Stringer. However, this is
+			// typically an expensive thing to do and should be avoided.
+			fmt.Println("Type: ", msg.Type())
+			fmt.Println("Message: ", msg)
+		}
+		return true
+	})
+
+	fmt.Println("Starting device monitor")
+	provider.Start()
+	fmt.Println("Started device monitor")
+
 	fmt.Println("listing devices from provider")
 	devices := provider.GetDevices()
 	for i, v := range devices {

gst/gst_device_provider.go

@@ -12,6 +12,7 @@ import (
 // DeviceMonitor is a Go representation of a GstDeviceMonitor.
 type DeviceProvider struct {
 	ptr *C.GstDeviceProvider
+	bus *Bus
 }
 
 func (d *DeviceProvider) GetDevices() []*Device {
@@ -27,3 +28,20 @@ func (d *DeviceProvider) GetDevices() []*Device {
 	})
 	return out
 }
+
+// GetPipelineBus returns the message bus for this pipeline.
+func (d *DeviceProvider) GetBus() *Bus {
+	if d.bus == nil {
+		cBus := C.gst_device_provider_get_bus(d.ptr)
+		d.bus = FromGstBusUnsafeFull(unsafe.Pointer(cBus))
+	}
+	return d.bus
+}
+
+func (d *DeviceProvider) Start() bool {
+	return gobool(C.gst_device_provider_start(d.ptr))
+}
+
+func (d *DeviceProvider) Stop() {
+	C.gst_device_provider_stop(d.ptr)
+}