fix: Don't gap jump at start of video if autoplay is not set (#3645)

Before, the video would automatically gap jump at the start, even if the video
was not yet playing. This meant that videos with a gap at the start would jump
ahead and get rid of the video poster, even if autoplay was set to false.

Closes: #3451

lib/media/gap_jumping_controller.js

@@ -154,8 +154,10 @@ shaka.media.GapJumpingController = class {
     }
     // Don't gap jump while paused, so that you don't constantly jump ahead
     // while paused on a livestream.  We make an exception for time 0, since we
-    // may be _required_ to seek on startup before play can begin.
-    if (this.video_.paused && this.video_.currentTime != 0) {
+    // may be _required_ to seek on startup before play can begin, but only if
+    // autoplay is enabled.
+    if (this.video_.paused && (this.video_.currentTime != 0 ||
+      (!this.video_.autoplay && this.video_.currentTime == 0))) {
       return;
     }
 

test/media/playhead_unit.js

@@ -1296,12 +1296,13 @@ describe('Playhead', () => {
     });
 
     // Regression test for https://github.com/google/shaka-player/issues/2987
-    it('does gap jump if paused at 0', () => {
+    it('does gap jump if paused at 0 and has autoplay', () => {
       const buffered = [{start: 10, end: 20}];
       video.buffered = createFakeBuffered(buffered);
       video.currentTime = 0;
       video.readyState = HTMLMediaElement.HAVE_ENOUGH_DATA;
       video.paused = true;
+      video.autoplay = true;
 
       config.jumpLargeGaps = true;
       playhead = new shaka.media.MediaSourcePlayhead(
@@ -1319,6 +1320,31 @@ describe('Playhead', () => {
       expect(video.currentTime).toBe(10);
     });
 
+    // Regression test for https://github.com/google/shaka-player/issues/3451
+    it('doesn\'t gap jump if paused at 0 and hasn\'t autoplay', () => {
+      const buffered = [{start: 10, end: 20}];
+      video.buffered = createFakeBuffered(buffered);
+      video.currentTime = 0;
+      video.readyState = HTMLMediaElement.HAVE_ENOUGH_DATA;
+      video.paused = true;
+      video.autoplay = false;
+
+      config.jumpLargeGaps = true;
+      playhead = new shaka.media.MediaSourcePlayhead(
+          video,
+          manifest,
+          config,
+          /* startTime= */ 0,
+          Util.spyFunc(onSeek),
+          Util.spyFunc(onEvent));
+
+      playhead.notifyOfBufferingChange();
+      jasmine.clock().tick(500);
+
+      // There should NOT have been a gap jump.
+      expect(video.currentTime).toBe(0);
+    });
+
     /**
      * @param {string} name
      * @param {SeekTestInfo} data