qcam: Update window title with FPS

Provide an average FPS in the QCam title bar to show the current rate of
frame processing.

The QCam compilation is updated to process the Qt MoC headers to support
signals and slots accordingly.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/qcam/main_window.cpp

@@ -28,6 +28,7 @@ MainWindow::MainWindow(const OptionsParser::Options &options)
 
 	title_ = "QCam " + QString::fromStdString(libcamera::version);
 	setWindowTitle(title_);
+	connect(&titleTimer_, SIGNAL(timeout()), this, SLOT(updateTitle()));
 
 	viewfinder_ = new ViewFinder(this);
 	setCentralWidget(viewfinder_);
@@ -54,6 +55,19 @@ MainWindow::~MainWindow()
 	CameraManager::instance()->stop();
 }
 
+void MainWindow::updateTitle()
+{
+	unsigned int duration = frameRateInterval_.elapsed();
+	unsigned int frames = framesCaptured_ - previousFrames_;
+	double fps = frames * 1000.0 / duration;
+
+	/* Restart counters. */
+	frameRateInterval_.start();
+	previousFrames_ = framesCaptured_;
+
+	setWindowTitle(title_ + " : " + QString::number(fps, 'f', 2) + " fps");
+}
+
 int MainWindow::openCamera()
 {
 	CameraManager *cm = CameraManager::instance();
@@ -148,6 +162,10 @@ int MainWindow::startCapture()
 		requests.push_back(request);
 	}
 
+	titleTimer_.start(2000);
+	frameRateInterval_.start();
+	previousFrames_ = 0;
+	framesCaptured_ = 0;
 	lastBufferTime_ = 0;
 
 	ret = camera_->start();
@@ -188,6 +206,9 @@ void MainWindow::stopCapture()
 	isCapturing_ = false;
 
 	config_.reset();
+
+	titleTimer_.stop();
+	setWindowTitle(title_);
 }
 
 void MainWindow::requestComplete(Request *request,
@@ -196,6 +217,8 @@ void MainWindow::requestComplete(Request *request,
 	if (request->status() == Request::RequestCancelled)
 		return;
 
+	framesCaptured_++;
+
 	Buffer *buffer = buffers.begin()->second;
 
 	double fps = buffer->timestamp() - lastBufferTime_;

src/qcam/main_window.h

@@ -10,7 +10,10 @@
 #include <map>
 #include <memory>
 
+#include <QElapsedTimer>
 #include <QMainWindow>
+#include <QObject>
+#include <QTimer>
 
 #include <libcamera/camera.h>
 #include <libcamera/stream.h>
@@ -28,10 +31,15 @@ enum {
 
 class MainWindow : public QMainWindow
 {
+	Q_OBJECT
+
 public:
 	MainWindow(const OptionsParser::Options &options);
 	~MainWindow();
 
+private Q_SLOTS:
+	void updateTitle();
+
 private:
 	int openCamera();
 
@@ -43,6 +51,8 @@ private:
 	int display(Buffer *buffer);
 
 	QString title_;
+	QTimer titleTimer_;
+
 	const OptionsParser::Options &options_;
 
 	std::shared_ptr<Camera> camera_;
@@ -51,6 +61,10 @@ private:
 
 	uint64_t lastBufferTime_;
 
+	QElapsedTimer frameRateInterval_;
+	uint32_t previousFrames_;
+	uint32_t framesCaptured_;
+
 	ViewFinder *viewfinder_;
 };
 

src/qcam/meson.build

@@ -7,14 +7,21 @@ qcam_sources = files([
     'viewfinder.cpp',
 ])
 
-import('qt5')
+qcam_moc_headers = files([
+    'main_window.h',
+])
+
+qt5 = import('qt5')
 qt5_dep = dependency('qt5',
                      method : 'pkg-config',
                      modules : ['Core', 'Gui', 'Widgets'],
                      required : false)
 
 if qt5_dep.found()
-    qcam  = executable('qcam', qcam_sources,
+    moc_files = qt5.preprocess(moc_headers: qcam_moc_headers,
+                               dependencies: qt5_dep)
+
+    qcam  = executable('qcam', qcam_sources, moc_files,
                        install : true,
                        dependencies : [libcamera_dep, qt5_dep],
                        cpp_args : '-DQT_NO_KEYWORDS')