lazy screencast.

internal/api/room/handler.go

@@ -63,7 +63,7 @@ func (h *RoomHandler) Route(r chi.Router) {
 	r.Route("/screen", func(r chi.Router) {
 		r.With(auth.CanWatchOnly).Get("/", h.screenConfiguration)
 		r.With(auth.CanWatchOnly).Get("/image", h.screenImageGet)
-		r.With(auth.CanWatchOnly).Get("/cast", h.screenCastGet)
+		r.With(auth.CanWatchOnly).Get("/cast.jpg", h.screenCastGet)
 
 		r.With(auth.AdminsOnly).Post("/", h.screenConfigurationChange)
 		r.With(auth.AdminsOnly).Get("/configurations", h.screenConfigurationsList)

internal/api/room/screen.go

@@ -103,7 +103,12 @@ func (h *RoomHandler) screenCastGet(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	bytes := screencast.Image()
+	bytes, err := screencast.Image()
+	if err != nil {
+		utils.HttpInternalServerError(w, err)
+		return
+	}
+
 	w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
 	w.Header().Set("Content-Type", "image/jpeg")
 	w.Write(bytes)

internal/capture/manager.go

@@ -51,12 +51,6 @@ func (manager *CaptureManagerCtx) Start() {
 		}
 	}
 
-	if manager.screencast.Enabled() {
-		if err := manager.screencast.createPipeline(); err != nil {
-			manager.logger.Panic().Err(err).Msg("unable to create screencast pipeline")
-		}
-	}
-
 	manager.desktop.OnBeforeScreenSizeChange(func() {
 		if manager.Streaming() {
 			manager.destroyVideoPipeline()
@@ -66,7 +60,7 @@ func (manager *CaptureManagerCtx) Start() {
 			manager.broadcast.destroyPipeline()
 		}
 
-		if manager.screencast.Enabled() {
+		if manager.screencast.Started() {
 			manager.screencast.destroyPipeline()
 		}
 	})
@@ -82,7 +76,7 @@ func (manager *CaptureManagerCtx) Start() {
 			}
 		}
 
-		if manager.screencast.Enabled() {
+		if manager.screencast.Started() {
 			if err := manager.screencast.createPipeline(); err != nil {
 				manager.logger.Panic().Err(err).Msg("unable to recreate screencast pipeline")
 			}

internal/capture/screencast.go

@@ -1,7 +1,9 @@
 package capture
 
 import (
-	"bytes"
+	"fmt"
+	"time"
+	"sync"
 
 	"github.com/rs/zerolog"
 	"github.com/rs/zerolog/log"
@@ -13,13 +15,17 @@ import (
 
 type ScreencastManagerCtx struct {
 	logger    zerolog.Logger
+	mu        sync.Mutex
 	config    *config.Capture
 	pipeline  *gst.Pipeline
 	enabled   bool
+	started   bool
 	shutdown  chan bool
 	refresh   chan bool
+	expires   time.Time
+	timeout   time.Duration
 	sample    chan types.Sample
-	image     *bytes.Buffer
+	image     types.Sample
 }
 
 func screencastNew(config *config.Capture) *ScreencastManagerCtx {
@@ -27,24 +33,34 @@ func screencastNew(config *config.Capture) *ScreencastManagerCtx {
 		logger:    log.With().Str("module", "capture").Str("submodule", "screencast").Logger(),
 		config:    config,
 		enabled:   config.Screencast,
+		started:   false,
 		shutdown:  make(chan bool),
 		refresh:   make(chan bool),
-		image:     new(bytes.Buffer),
+		timeout:   10 * time.Second,
+	}
+
+	if !manager.enabled {
+		return manager
 	}
 
 	go func() {
+		ticker := time.NewTicker(1 * time.Second)
 		manager.logger.Debug().Msg("subroutine started")
 
 		for {
 			select {
 			case <-manager.shutdown:
 				manager.logger.Debug().Msg("shutting down")
+				ticker.Stop()
 				return
 			case <-manager.refresh:
 				manager.logger.Debug().Msg("subroutine updated")
 			case sample := <-manager.sample:
-				manager.image.Reset()
-				manager.image.Write(sample.Data)
+				manager.image = sample
+			case <-ticker.C:
+				if manager.started && time.Now().After(manager.expires) {
+					manager.stop()
+				}
 			}
 		}
 	}()
@@ -52,25 +68,61 @@ func screencastNew(config *config.Capture) *ScreencastManagerCtx {
 	return manager
 }
 
-func (manager *ScreencastManagerCtx) Start() error {
-	manager.enabled = true
-	return manager.createPipeline()
-}
-
-func (manager *ScreencastManagerCtx) Stop() {
-	manager.enabled = false
-	manager.destroyPipeline()
-}
-
 func (manager *ScreencastManagerCtx) Enabled() bool {
 	return manager.enabled
 }
 
-func (manager *ScreencastManagerCtx) Image() []byte {
-	return manager.image.Bytes()
+func (manager *ScreencastManagerCtx) Started() bool {
+	return manager.started
+}
+
+func (manager *ScreencastManagerCtx) Image() ([]byte, error) {
+	manager.expires = time.Now().Add(manager.timeout)
+
+	if !manager.started {
+		err := manager.start()
+		if err != nil {
+			return nil, err
+		}
+
+		select {
+		case sample := <-manager.sample:
+			return sample.Data, nil
+		case <-time.After(1 * time.Second):
+			return nil, fmt.Errorf("timeouted")
+		}
+	}
+
+	if manager.image.Data == nil {
+		return nil, fmt.Errorf("image sample not found")
+	}
+
+	return manager.image.Data, nil
+}
+
+func (manager *ScreencastManagerCtx) start() error {
+	if !manager.enabled {
+		return fmt.Errorf("screenshot pipeline not enabled")
+	}
+
+	err := manager.createPipeline()
+	if err != nil {
+		return err
+	}
+
+	manager.started = true
+	return nil
+}
+
+func (manager *ScreencastManagerCtx) stop() {
+	manager.started = false
+	manager.destroyPipeline()
 }
 
 func (manager *ScreencastManagerCtx) createPipeline() error {
+	manager.mu.Lock()
+	defer manager.mu.Unlock()
+
 	var err error
 
 	manager.logger.Info().
@@ -98,6 +150,9 @@ func (manager *ScreencastManagerCtx) createPipeline() error {
 }
 
 func (manager *ScreencastManagerCtx) destroyPipeline() {
+	manager.mu.Lock()
+	defer manager.mu.Unlock()
+
 	if manager.pipeline == nil {
 		return
 	}

internal/types/capture.go

@@ -13,10 +13,9 @@ type BroadcastManager interface {
 }
 
 type ScreencastManager interface {
-	Start() error
-	Stop()
 	Enabled() bool
-	Image() []byte
+	Started() bool
+	Image() ([]byte, error)
 }
 
 type CaptureManager interface {