1293529 - twitter card images often appear as blank white space

Status: RESOLVED WORKSFORME

(Core :: Graphics: ImageLib, defect)

Description

[Ben Kelly [:bkelly, not reviewing]]

I've noticed recently that twitter card images often appear as blank space.  It happens intermittently so its difficult to provide exact STR, but I see it on a daily basis at the moment.

The one pattern I've noticed is that this seems to happen when someone replies to a twitter card with an image, but the original tweet was some time ago in my timeline.  So the reply resurrects that original tweet in order to show the conversation threading.  In this case I believe an orphaned DOM element is being put back into the page after some time.

Seth, is it possible that we are discarding decoded data while the image is out of the DOM, but failing to decode again once its put back into the DOM?

Another possibility would be that twitter is calling revokeObjectUrl() on the image src url or something.

Comment 1

[Ben Kelly [:bkelly, not reviewing]]

I feel like I see this most frequently on nightly, but not 100% sure its limited to nightly.  I will try running some of the other branches for a while to see if it reproduces there.

Comment 2

[Seth Fowler [:seth] [:s2h]]

(In reply to Ben Kelly [:bkelly] from comment #0)
> Seth, is it possible that we are discarding decoded data while the image is
> out of the DOM, but failing to decode again once its put back into the DOM?

Possibly, but I'd be surprised. The way things are structured, if the frame for a DOM element is getting drawn, it's basically impossible to avoid triggering a decode.

> Another possibility would be that twitter is calling revokeObjectUrl() on
> the image src url or something.

That shouldn't break anything as long as they kept the DOM Image object alive, but if they got rid of that too, (or simply didn't reuse the same one) that would definitely break stuff.

(In reply to Ben Kelly [:bkelly] from comment #1)
> I feel like I see this most frequently on nightly, but not 100% sure its
> limited to nightly.  I will try running some of the other branches for a
> while to see if it reproduces there.

It'd be good to know if that's the case, yeah.

What I would actually suspect is most likely (just intuition, this could well be wrong) is that this is an invalidation issue. We may just be failing to repaint the decoded image correctly for some reason. If this is some sort of race, recent changes on Nightly could well be tickling it more, because the timing as to when the decoded version of an image becomes available has changed.

To know how to move forward, it'd be good to get confirmation as to whether this only happens on Nightly.

Andrew, I'm going to go ahead and put this on your radar.

Comment 3

[Ben Kelly [:bkelly, not reviewing]]

Attachment: Screenshot 2016-08-09 12.51.54.png

Seems this is a site problem.

I noticed it again today and inspected the element.  As far as I can tell there is no <img> element and no background-image css.  There is also no embedded iframe.

Let's leave this bug open for the moment while I ask twitter.

Comment 4

[Henri Sivonen (:hsivonen)]

These images are consistently blank for me in Fennec Nightly on https://mobile.twitter.com/. Disabling tracking protection and add-ons does not help. I do see the images in desktop Firefox on https://twitter.com/. I also see the images on https://mobile.twitter.com/ in Chrome for Android.

Comment 5

[Andrew Overholt [:overholt]]

(Likely duping this very soon)

Comment 6

[Mike Taylor [:miketaylr]]

Comment #4 make me think this was possibly Bug 1301106 (or at least what Henri is seeing). Have you seen this again Ben?

Comment 7

[Ben Kelly [:bkelly, not reviewing]]

When I asked on the twitter thread a while ago they indicated this was a known issue on their side.  I do still see it periodically.  I mostly see it on desktop, though.  I think its different from the nightly fennec image issue.

Comment 8

[Mike Taylor [:miketaylr]]

(In reply to Ben Kelly [:bkelly] from comment #7)
> When I asked on the twitter thread a while ago they indicated this was a
> known issue on their side.  I do still see it periodically.  I mostly see it
> on desktop, though.  I think its different from the nightly fennec image
> issue.

Thanks Ben. I guess we just keep an eye on it then, since they know about it (and hopefully will fix it).

Comment 9

[Desigan Chinniah [:cyberdees] [:dees] [London - GMT]]

Ben - are you still reproducing? If so — perhaps worth highlighting it via our DL?

Comment 10

[Ben Kelly [:bkelly, not reviewing]]

I haven't seen this for a while.