Phase 7 step 1

apps/LoopThroughWithOpenGLCompositing/videoio/VideoBackend.cpp

@@ -26,46 +26,86 @@ void VideoBackend::ReleaseResources()
 {
 	if (mVideoIODevice)
 		mVideoIODevice->ReleaseResources();
+	if (!VideoBackendLifecycle::CanTransition(mLifecycle.State(), VideoBackendLifecycleState::Stopped))
+		ApplyLifecycleFailure("Video backend resources released before lifecycle completed.");
+	ApplyLifecycleTransition(VideoBackendLifecycleState::Stopped, "Video backend resources released.");
+}
+
+VideoBackendLifecycleState VideoBackend::LifecycleState() const
+{
+	return mLifecycle.State();
 }
 
 bool VideoBackend::DiscoverDevicesAndModes(const VideoFormatSelection& videoModes, std::string& error)
 {
-	return mVideoIODevice->DiscoverDevicesAndModes(videoModes, error);
+	ApplyLifecycleTransition(VideoBackendLifecycleState::Discovering, "Discovering video backend devices and modes.");
+	if (mVideoIODevice->DiscoverDevicesAndModes(videoModes, error))
+		return ApplyLifecycleTransition(VideoBackendLifecycleState::Discovered, "Video backend devices and modes discovered.");
+
+	ApplyLifecycleFailure(error.empty() ? "Video backend discovery failed." : error);
+	return false;
 }
 
 bool VideoBackend::SelectPreferredFormats(const VideoFormatSelection& videoModes, bool outputAlphaRequired, std::string& error)
 {
-	return mVideoIODevice->SelectPreferredFormats(videoModes, outputAlphaRequired, error);
+	ApplyLifecycleTransition(VideoBackendLifecycleState::Configuring, "Selecting preferred video backend formats.");
+	if (mVideoIODevice->SelectPreferredFormats(videoModes, outputAlphaRequired, error))
+		return true;
+
+	ApplyLifecycleFailure(error.empty() ? "Video backend format selection failed." : error);
+	return false;
 }
 
 bool VideoBackend::ConfigureInput(const VideoFormat& inputVideoMode, std::string& error)
 {
-	return mVideoIODevice->ConfigureInput(
+	if (mLifecycle.State() != VideoBackendLifecycleState::Configuring)
+		ApplyLifecycleTransition(VideoBackendLifecycleState::Configuring, "Configuring video backend input.");
+	if (!mVideoIODevice->ConfigureInput(
 		[this](const VideoIOFrame& frame) { HandleInputFrame(frame); },
 		inputVideoMode,
-		error);
+		error))
+	{
+		ApplyLifecycleFailure(error.empty() ? "Video backend input configuration failed." : error);
+		return false;
+	}
+	return true;
 }
 
 bool VideoBackend::ConfigureOutput(const VideoFormat& outputVideoMode, bool externalKeyingEnabled, std::string& error)
 {
-	return mVideoIODevice->ConfigureOutput(
+	if (mLifecycle.State() != VideoBackendLifecycleState::Configuring)
+		ApplyLifecycleTransition(VideoBackendLifecycleState::Configuring, "Configuring video backend output.");
+	if (!mVideoIODevice->ConfigureOutput(
 		[this](const VideoIOCompletion& completion) { HandleOutputFrameCompletion(completion); },
 		outputVideoMode,
 		externalKeyingEnabled,
-		error);
+		error))
+	{
+		ApplyLifecycleFailure(error.empty() ? "Video backend output configuration failed." : error);
+		return false;
+	}
+	return ApplyLifecycleTransition(VideoBackendLifecycleState::Configured, "Video backend configured.");
 }
 
 bool VideoBackend::Start()
 {
+	ApplyLifecycleTransition(VideoBackendLifecycleState::Prerolling, "Video backend preroll starting.");
 	const bool started = mVideoIODevice->Start();
-	PublishBackendStateChanged(started ? "started" : "start-failed", started ? "Video backend started." : StatusMessage());
+	if (started)
+		ApplyLifecycleTransition(VideoBackendLifecycleState::Running, "Video backend started.");
+	else
+		ApplyLifecycleFailure(StatusMessage().empty() ? "Video backend start failed." : StatusMessage());
 	return started;
 }
 
 bool VideoBackend::Stop()
 {
+	ApplyLifecycleTransition(VideoBackendLifecycleState::Stopping, "Video backend stopping.");
 	const bool stopped = mVideoIODevice->Stop();
-	PublishBackendStateChanged(stopped ? "stopped" : "stop-failed", stopped ? "Video backend stopped." : StatusMessage());
+	if (stopped)
+		ApplyLifecycleTransition(VideoBackendLifecycleState::Stopped, "Video backend stopped.");
+	else
+		ApplyLifecycleFailure(StatusMessage().empty() ? "Video backend stop failed." : StatusMessage());
 	return stopped;
 }
 
@@ -198,7 +238,7 @@ void VideoBackend::PublishStatus(bool externalKeyingConfigured, const std::strin
 		externalKeyingConfigured,
 		ExternalKeyingActive(),
 		StatusMessage());
-	PublishBackendStateChanged("status", StatusMessage());
+	PublishBackendStateChanged(VideoBackendLifecycle::StateName(mLifecycle.State()), StatusMessage());
 }
 
 void VideoBackend::ReportNoInputDeviceSignalStatus()
@@ -240,7 +280,7 @@ void VideoBackend::HandleOutputFrameCompletion(const VideoIOCompletion& completi
 	AccountForCompletionResult(completion.result);
 	if (!rendered)
 	{
-		PublishBackendStateChanged("output-render-failed", "Output frame render request failed; skipping schedule for this frame.");
+		ApplyLifecycleTransition(VideoBackendLifecycleState::Degraded, "Output frame render request failed; skipping schedule for this frame.");
 		return;
 	}
 
@@ -283,6 +323,32 @@ void VideoBackend::RecordFramePacing(VideoIOCompletionResult completionResult)
 	PublishTimingSample("VideoBackend", "smoothedCompletionInterval", mSmoothedCompletionIntervalMilliseconds, "ms");
 }
 
+bool VideoBackend::ApplyLifecycleTransition(VideoBackendLifecycleState state, const std::string& message)
+{
+	const VideoBackendLifecycleTransition transition = mLifecycle.TransitionTo(state, message);
+	if (!transition.accepted)
+	{
+		PublishBackendStateChanged(VideoBackendLifecycle::StateName(transition.current), transition.errorMessage);
+		return false;
+	}
+
+	PublishBackendStateChanged(VideoBackendLifecycle::StateName(transition.current), message);
+	return true;
+}
+
+bool VideoBackend::ApplyLifecycleFailure(const std::string& message)
+{
+	const VideoBackendLifecycleTransition transition = mLifecycle.Fail(message);
+	if (!transition.accepted)
+	{
+		PublishBackendStateChanged(VideoBackendLifecycle::StateName(transition.current), transition.errorMessage);
+		return false;
+	}
+
+	PublishBackendStateChanged(VideoBackendLifecycle::StateName(transition.current), message);
+	return true;
+}
+
 void VideoBackend::PublishBackendStateChanged(const std::string& state, const std::string& message)
 {
 	try