From 9e95c15a6754fa571199c36d73ac2dc1d45e5c64 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Fri, 21 Jul 2023 22:39:02 +0200
Subject: [PATCH] Propagate errors on video opening back to the UI.

This is kludgy, but it will work for now.
---
 mainwindow.cpp   |  5 ++++-
 video_widget.cpp | 33 +++++++++++++++++++++++----------
 video_widget.h   |  5 +++--
 3 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/mainwindow.cpp b/mainwindow.cpp
index 7eec2cb..5a1b745 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -42,7 +42,10 @@ MainWindow::MainWindow(EventsModel *events, PlayersModel *players,
 	ui = new Ui::MainWindow;
 	ui->setupUi(this);
 
-	ui->video->open("/home/sesse/dev/stats/ultimate-prores.mkv");
+	if (!ui->video->open("/home/sesse/dev/stats/ultimate-prores.mkv")) {
+		// TODO: Pop up a dialog box here instead
+		fprintf(stderr, "WARNING: Video opening failed\n");
+	}
 	ui->video->play();
 
 	ui->event_view->setModel(events);
diff --git a/video_widget.cpp b/video_widget.cpp
index 7bafa64..e6708a9 100644
--- a/video_widget.cpp
+++ b/video_widget.cpp
@@ -594,30 +594,40 @@ void VideoWidget::fixup_zoom_matrix()
 	zoom_matrix[7] = std::max(zoom_matrix[7], 1.0 - zoom_matrix[4]);  // Top side (y=1).
 }
 
-void VideoWidget::open(const string &filename)
+bool VideoWidget::open(const string &filename)
 {
 	stop();
 	internal_rewind();
 	pathname = filename;
 	play();
+
+	while (running == STARTING) {
+		// Poor man's condition variable...
+		usleep(10000);
+		sched_yield();
+	}
+	return (running != VIDEO_FILE_ERROR);	
 }
 
 void VideoWidget::play()
 {
-	if (running) {
+	if (running != NOT_RUNNING && running != VIDEO_FILE_ERROR) {
 		std::lock_guard<std::mutex> lock(queue_mu);
 		command_queue.push_back(QueuedCommand { QueuedCommand::RESUME });
 		producer_thread_should_quit.wakeup();
 		return;
 	}
-	running = true;
+	running = STARTING;
 	producer_thread_should_quit.unquit();
+	if (producer_thread.joinable()) {
+		producer_thread.join();
+	}
 	producer_thread = std::thread(&VideoWidget::producer_thread_func, this);
 }
 
 void VideoWidget::pause()
 {
-	if (!running) {
+	if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 		return;
 	}
 	std::lock_guard<std::mutex> lock(queue_mu);
@@ -627,7 +637,7 @@ void VideoWidget::pause()
 
 void VideoWidget::seek(int64_t relative_seek_ms)
 {
-	if (!running) {
+	if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 		return;
 	}
 	std::lock_guard<std::mutex> lock(queue_mu);
@@ -637,7 +647,7 @@ void VideoWidget::seek(int64_t relative_seek_ms)
 
 void VideoWidget::seek_frames(int64_t relative_seek_frames)
 {
-	if (!running) {
+	if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 		return;
 	}
 	std::lock_guard<std::mutex> lock(queue_mu);
@@ -647,7 +657,7 @@ void VideoWidget::seek_frames(int64_t relative_seek_frames)
 
 void VideoWidget::seek_absolute(int64_t position_ms)
 {
-	if (!running) {
+	if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 		return;
 	}
 	std::lock_guard<std::mutex> lock(queue_mu);
@@ -657,10 +667,9 @@ void VideoWidget::seek_absolute(int64_t position_ms)
 
 void VideoWidget::stop()
 {
-	if (!running) {
+	if (running == NOT_RUNNING || running == VIDEO_FILE_ERROR) {
 		return;
 	}
-	running = false;
 	producer_thread_should_quit.quit();
 	producer_thread.join();
 }
@@ -669,7 +678,9 @@ void VideoWidget::producer_thread_func()
 {
 	if (!producer_thread_should_quit.should_quit()) {
 		if (!play_video(pathname)) {
-			// TODO: Send the error back to the UI somehow.
+			running = VIDEO_FILE_ERROR;
+		} else {
+			running = NOT_RUNNING;
 		}
 	}
 }
@@ -875,6 +886,8 @@ bool VideoWidget::play_video(const string &pathname)
 
 	internal_rewind();
 
+	running = RUNNING;
+
 	// Main loop.
 	int consecutive_errors = 0;
 	double rate = 1.0;
diff --git a/video_widget.h b/video_widget.h
index dc7d0ab..c0f28d7 100644
--- a/video_widget.h
+++ b/video_widget.h
@@ -25,7 +25,7 @@ public:
 	VideoWidget(QWidget *parent);
 	~VideoWidget() { stop(); }
 
-	void open(const std::string &filename);
+	bool open(const std::string &filename);  // False on error.
 	void play();
 	uint64_t get_position() const { return last_position; }  // In milliseconds.
 	void pause();
@@ -77,7 +77,8 @@ private:
 	int64_t pts_origin;
 	int64_t last_pts;
 	std::atomic<uint64_t> last_position{0};  // TODO: sort of redundant wrt. last_pts (but this one can be read from the other thread)
-	std::atomic<bool> running{false};
+	enum RunState { NOT_RUNNING, STARTING, RUNNING, VIDEO_FILE_ERROR };  // NOT_RUNNING and VIDEO_FILE_ERROR both imply that the thread isn't running and can freely be restarted.
+	std::atomic<RunState> running{NOT_RUNNING};
 	bool paused = false;
 	std::chrono::steady_clock::time_point start, next_frame_start, last_frame;
 
-- 
2.39.2