Add GetDisplayMedia

* Add selectScreen to select all registered drivers that can screenshare
* Add GetDisplayMedia
* Add screenshare example

examples/screenshare/README.md

@@ -0,0 +1,29 @@
+## Instructions
+
+### Download screenshare
+
+```
+go get github.com/pion/mediadevices/examples/screenshare
+```
+
+### Open example page
+
+[jsfiddle.net](https://jsfiddle.net/z7ms3u5r/) you should see two text-areas and a 'Start Session' button
+
+### Run screenshare with your browsers SessionDescription as stdin
+
+In the jsfiddle the top textarea is your browser, copy that and:
+
+#### Linux
+
+Run `echo $BROWSER_SDP | screenshare`
+
+### Input screenshare's SessionDescription into your browser
+
+Copy the text that `screenshare` just emitted and copy into second text area
+
+### Hit 'Start Session' in jsfiddle, enjoy your video!
+
+A video should start playing in your browser above the input boxes, and will continue playing until you close the application.
+
+Congrats, you have used pion-WebRTC! Now start building something cool

examples/screenshare/main.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/pion/mediadevices"
+	"github.com/pion/mediadevices/examples/internal/signal"
+	_ "github.com/pion/mediadevices/pkg/codec/openh264" // This is required to register h264 video encoder
+	_ "github.com/pion/mediadevices/pkg/codec/opus"     // This is required to register opus audio encoder
+	_ "github.com/pion/mediadevices/pkg/codec/vpx"
+	"github.com/pion/mediadevices/pkg/frame"
+	"github.com/pion/webrtc/v2"
+)
+
+const (
+	videoCodecName = webrtc.VP8
+)
+
+func main() {
+	config := webrtc.Configuration{
+		ICEServers: []webrtc.ICEServer{
+			{
+				URLs: []string{"stun:stun.l.google.com:19302"},
+			},
+		},
+	}
+
+	// Wait for the offer to be pasted
+	offer := webrtc.SessionDescription{}
+	signal.Decode(signal.MustReadStdin(), &offer)
+
+	// Create a new RTCPeerConnection
+	mediaEngine := webrtc.MediaEngine{}
+	if err := mediaEngine.PopulateFromSDP(offer); err != nil {
+		panic(err)
+	}
+	api := webrtc.NewAPI(webrtc.WithMediaEngine(mediaEngine))
+	peerConnection, err := api.NewPeerConnection(config)
+	if err != nil {
+		panic(err)
+	}
+
+	// Set the handler for ICE connection state
+	// This will notify you when the peer has connected/disconnected
+	peerConnection.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {
+		fmt.Printf("Connection State has changed %s \n", connectionState.String())
+	})
+
+	md := mediadevices.NewMediaDevices(peerConnection)
+
+	s, err := md.GetDisplayMedia(mediadevices.MediaStreamConstraints{
+		Video: func(c *mediadevices.MediaTrackConstraints) {
+			c.CodecName = videoCodecName
+			c.FrameFormat = frame.FormatI444
+			c.Enabled = true
+			c.Width = 640
+			c.Height = 480
+			c.BitRate = 100000 // 100kbps
+		},
+	})
+	if err != nil {
+		panic(err)
+	}
+
+	for _, tracker := range s.GetTracks() {
+		t := tracker.Track()
+		tracker.OnEnded(func(err error) {
+			fmt.Printf("Track (ID: %s, Label: %s) ended with error: %v\n",
+				t.ID(), t.Label(), err)
+		})
+		_, err = peerConnection.AddTrack(t)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	// Tweak transceiver direction to work with Firefox
+	for _, t := range peerConnection.GetTransceivers() {
+		t.Direction = webrtc.RTPTransceiverDirectionSendonly
+	}
+
+	// Set the remote SessionDescription
+	err = peerConnection.SetRemoteDescription(offer)
+	if err != nil {
+		panic(err)
+	}
+
+	// Create an answer
+	answer, err := peerConnection.CreateAnswer(nil)
+	if err != nil {
+		panic(err)
+	}
+
+	// Sets the LocalDescription, and starts our UDP listeners
+	err = peerConnection.SetLocalDescription(answer)
+	if err != nil {
+		panic(err)
+	}
+
+	// Output the answer in base64 so we can paste it in browser
+	fmt.Println(signal.Encode(answer))
+	select {}
+}

mediadevices.go

@@ -13,6 +13,7 @@ var errNotFound = fmt.Errorf("failed to find the best driver that fits the const
 
 // MediaDevices is an interface that's defined on https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices
 type MediaDevices interface {
+	GetDisplayMedia(constraints MediaStreamConstraints) (MediaStream, error)
 	GetUserMedia(constraints MediaStreamConstraints) (MediaStream, error)
 	EnumerateDevices() []MediaDeviceInfo
 }
@@ -75,6 +76,34 @@ func WithTrackGenerator(gen TrackGenerator) MediaDevicesOption {
 	}
 }
 
+// GetDisplayMedia prompts the user to select and grant permission to capture the contents
+// of a display or portion thereof (such as a window) as a MediaStream.
+// Reference: https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getDisplayMedia
+func (m *mediaDevices) GetDisplayMedia(constraints MediaStreamConstraints) (MediaStream, error) {
+	trackers := make([]Tracker, 0)
+
+	var videoConstraints MediaTrackConstraints
+	if constraints.Video != nil {
+		constraints.Video(&videoConstraints)
+	}
+
+	if videoConstraints.Enabled {
+		tracker, err := m.selectScreen(videoConstraints)
+		if err != nil {
+			return nil, err
+		}
+
+		trackers = append(trackers, tracker)
+	}
+
+	s, err := NewMediaStream(trackers...)
+	if err != nil {
+		return nil, err
+	}
+
+	return s, nil
+}
+
 // GetUserMedia prompts the user for permission to use a media input which produces a MediaStream
 // with tracks containing the requested types of media.
 // Reference: https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia
@@ -212,6 +241,27 @@ func (m *mediaDevices) selectVideo(constraints MediaTrackConstraints) (Tracker,
 	return newVideoTrack(&m.MediaDevicesOptions, d, c)
 }
 
+func (m *mediaDevices) selectScreen(constraints MediaTrackConstraints) (Tracker, error) {
+	typeFilter := driver.FilterVideoRecorder()
+	screenFilter := driver.FilterDeviceType(driver.Screen)
+	filter := func(d driver.Driver) bool {
+		return typeFilter(d) && screenFilter(d)
+	}
+	if constraints.DeviceID != "" {
+		idFilter := driver.FilterID(constraints.DeviceID)
+		filter = func(d driver.Driver) bool {
+			return typeFilter(d) && screenFilter(d) && idFilter(d)
+		}
+	}
+
+	d, c, err := selectBestDriver(filter, constraints)
+	if err != nil {
+		return nil, err
+	}
+
+	return newVideoTrack(&m.MediaDevicesOptions, d, c)
+}
+
 func (m *mediaDevices) EnumerateDevices() []MediaDeviceInfo {
 	drivers := driver.GetManager().Query(
 		driver.FilterFn(func(driver.Driver) bool { return true }))