Investigate inconsistent behaviour around stopping/finished and playing next item

[caprica]

For a long time, the idiom in vlcj to play multiple media one after the other was to wait for a finished event, then start playing the next media in the finished handler.

With a recent change to 4.x of VLC, the "end reached" event used by vlcj became instead "stopping".

The event sequence should be:

• playing
• stopping
• stopped
• playing
• stopping
• stopped
• -playing
• ...etc...

Now, following that same idiom the events are inconsistently (a race):

• playing
• stopping
• playing
• stopping
• playing
• ...etc...

So the stopped event does not fire.

In theory, the fix is just to move "finished" processing to "stop" - making sure not to request new media until after a stopped event is received.

[caprica]

Demonstration of issue, toggle the boolean "bug" to switch behaviours:

import uk.co.caprica.vlcj.player.base.MediaPlayer;
import uk.co.caprica.vlcj.player.base.OneShotMediaPlayerEventListener;
import uk.co.caprica.vlcj.player.component.EmbeddedMediaPlayerComponent;

import javax.swing.JFrame;
import java.util.concurrent.atomic.AtomicInteger;

public class EventTest {

    private static EmbeddedMediaPlayerComponent mediaPlayerComponnt;

    private static final AtomicInteger counter = new AtomicInteger(0);

    private static final boolean bug = true;

    private static final String MEDIA_1 = "movie1.mp4";
    private static final String MEDIA_2 = "movie2.mp4";

    public static void main(String[] args) {
        mediaPlayerComponnt = new EmbeddedMediaPlayerComponent() {
            @Override
            public void playing(MediaPlayer mediaPlayer) {
                System.out.printf("%02d PLAYING%n", counter.incrementAndGet());
            }

            @Override
            public void stopped(MediaPlayer mediaPlayer) {
                System.out.printf("%02d STOPPED, BUG IS %s%n", counter.incrementAndGet(), bug);
                if (!bug) {
                    mediaPlayer.submit(() -> {
                        mediaPlayer.media().play(MEDIA_2);
                    });
                }
            }

            @Override
            public void stopping(MediaPlayer mediaPlayer) {
                System.out.printf("%02d STOPPING, BUG IS %s%n", counter.incrementAndGet(), bug);
                if (bug) {
                    mediaPlayer.submit(() -> {
                        mediaPlayer.media().play(MEDIA_2);
                    });
                }
            }
        };

        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(mediaPlayerComponnt);
        f.setSize(800, 600);
        f.setVisible(true);

        mediaPlayerComponnt.mediaPlayer().events().addMediaPlayerEventListener(new OneShotMediaPlayerEventListener() {
            @Override
            public void playing(MediaPlayer mediaPlayer) {
                mediaPlayer.controls().setPosition(0.99f);
                done(mediaPlayer);
            }
        });

        mediaPlayerComponnt.mediaPlayer().media().play(MEDIA_1);
    }
}

[caprica]

There was some discussion a while ago now at the VLC GitLab issues, but nothing has changed so far.