qcam: Move requestCompleted signal mapping

The MainWindow connects a handler to the Camera requestCompleted signal
when the camera is opened, but never disconnects it.

Move the connection to the startCapture() function, and ensure that it
is disconnected again when the stream is stopped.

This ensures that we can successfully tear down the stream, and restart
with a new camera.

Introducing the error_disconnect cleanup path in start_capture
identified that we left the camera in the start state, thus we also add
a call to camera->stop() when disconnecting the signal connection.

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

src/qcam/main_window.cpp

@@ -113,8 +113,6 @@ int MainWindow::openCamera(CameraManager *cm)
 
 	std::cout << "Using camera " << camera_->name() << std::endl;
 
-	camera_->requestCompleted.connect(this, &MainWindow::requestComplete);
-
 	return 0;
 }
 
@@ -212,17 +210,23 @@ int MainWindow::startCapture()
 		goto error;
 	}
 
+	camera_->requestCompleted.connect(this, &MainWindow::requestComplete);
+
 	for (Request *request : requests) {
 		ret = camera_->queueRequest(request);
 		if (ret < 0) {
 			std::cerr << "Can't queue request" << std::endl;
-			goto error;
+			goto error_disconnect;
 		}
 	}
 
 	isCapturing_ = true;
 	return 0;
 
+error_disconnect:
+	camera_->requestCompleted.disconnect(this, &MainWindow::requestComplete);
+	camera_->stop();
+
 error:
 	for (Request *request : requests)
 		delete request;
@@ -249,6 +253,8 @@ void MainWindow::stopCapture()
 	if (ret)
 		std::cout << "Failed to stop capture" << std::endl;
 
+	camera_->requestCompleted.disconnect(this, &MainWindow::requestComplete);
+
 	for (auto &iter : mappedBuffers_) {
 		void *memory = iter.second.first;
 		unsigned int length = iter.second.second;