shaka.text.Cue.textAlign is getting mangled

[chrisfillmore]

Have you read the FAQ and checked for duplicate issues:
Yes

What version of Shaka Player are you using:
2.2.0

Can you reproduce the issue with our latest release version:
Yes

Can you reproduce the issue with the latest code from master:
Unknown

Are you using the demo app or your own custom app:
Custom app demo app

If custom app, can you reproduce the issue using our demo app:
No. Is there demo content that includes external vtt files (not embedded)? I'm not sure if this makes a difference. Yes

What browser and OS are you using:
MacOS 10.12.6
Chrome 60.0.3112.101

What are the manifest and license server URIs:
I can send a demo application to reproduce, if necessary. Sent manifest and license url to shaka-player-issues

What did you do?
Watched a stream with external vtt tracks (edit: left-aligned)

What did you expect to happen?
Stream to play normally and subtitles to appear left-aligned ('left' is the alignment value provided by the vtt tracks).

What actually happened?
Chrome produces warnings saying The provided value 'undefined' is not a valid enum value of type AlignSetting. The subtitles themselves also appear to be center-aligned (although they're oddly cropped... but this may be an issue in our demo application). I took some screenshots of the subtitles but I think they're a bit besides the point. I think this is the problem:

The warning comes from shaka.text.SimpleTextDisplayer.prototype.convertToTextTrackCue_, here:

vttCue.align = shakaCue.textAlign;

The value of shakaCue.textAlign is undefined.

This looks like a mangling / minification bug, because I don't get it when I run Shaka uncompiled.

When I set a breakpoint and inspect in compiled mode, I see that shaka.text.Cue.textAlign looks like:

So, when textAlign gets set on the cue point in shaka.text.VttTextParser.setTextAlign_, here:

cue.textAlign = Cue.textAlign[align.toUpperCase()];

... the value is undefined. I don't see this problem in Shaka v2.1.7.

[chrisfillmore]

Would you like me to send a demo app to reproduce?

[joeyparrish]

I haven't tried yet, but it sounds easy enough to reproduce.

It shouldn't be undefined, because the regex looks like this:

  if ((results = /^align:(start|middle|center|end|left|right)$/.exec(word))) {
    VttTextParser.setTextAlign_(cue, results[1]);

So results[1] should only be one of those strings in the regex alternation. Later, when we do this:

    cue.textAlign = Cue.textAlign[align.toUpperCase()];

The value of align should definitely be one of the enumerated values.

We'll dig into this. Thanks for the report!

[joeyparrish]

Okay, I thought it would be easy to repro, but I can't so far. I have tried both "Angel One" (WebVTT subs) and "Sintel" (w/ MP4-embedded VTT text). Can you please send a demo asset or app that reproduces the problem?

[chrisfillmore]

It's not the value of results[1] that is problematic. The value of shaka.text.Cue.textAlign in compiled Shaka is:

{
  Hc: "end",
  Ic: "left",
  Mc: "right",
  Nc: "start",
  tb: "center"
}

So when we ask for shaka.text.Cue.textAlign['LEFT'], the value is undefined.

I can send a demo over in just a bit. [edit: demo app sent]

[chrisfillmore]

I sent another email just now with repro steps for the Shaka demo app.

[ismena]

Received, thanks!

[joeyparrish]

It seems that we didn't catch this because we aren't testing with text streams that use these attributes.

[joeyparrish]

Cherry-picked to v2.2.1