1255928 - Newtab controls blink while page loads

Status: REOPENED

(Core :: Layout, defect)

Description

[Oriol Brufau [:Oriol]]

1. Go to about:newtab
2. Hover a link. The controls (pin/remove) appear.
3. Click that link
4. While you still see the about:newpage (e10s must be disabled to prevent it from disappearing immediately), move the mouse and hover another link
5. The controls of the now hovered link and the clicked one blink.

This is hard to reproduce when the link loads fast, so you can also use this PHP script in http://localhost/test which sleeps 120 seconds after flushing some whitespace:
> <?php
> echo str_pad('',4096);
> ob_end_flush();
> ob_flush();
> flush();
> ob_start();
> 
> set_time_limit(0);
> sleep(120);
> ?>

And to reproduce the problem, use another file with
>  <style>
>  .buggy {
>    display: inline-block;
>    height: 30px;
>    width: 30px;
>    background: red;
>    opacity: 0;
>    transition: opacity 100ms ease-out;
>  }
>  li:hover > .buggy {
>    opacity: 1;
>  }
>  </style>
>  <ol>
>    <li>
>      <a href="http://localhost/test/">Click me</a>
>      <span class="buggy"></span>
>    </li>
>    <li>
>      Then hover me
>      <span class="buggy"></span>
>    </li>
>  </ol>

This started when bug 980770 enabled layers.offmainthreadcomposition.async-animations

Before that, if I enable the pref manually, the cause was https://hg.mozilla.org/mozilla-central/rev/6a4a22732aed from bug 927349.

Comment 1

[Brian Birtles (:birtles)]

That's odd. I wonder if it is related to the fact that we're about to unload the current page, or simply due to the link being in the active state.

I'll see if there's someone to look into it in Q2.

Comment 2

[Timothy Nikkel (:tnikkel)]

Maybe the page is told it's no longer active (but we are still painting it while the next page loads) and so it doesn't animate. But the off main thread animation doesn't know about the page no longer being active?

Comment 3

[BMO Automation]

Per policy at https://wiki.mozilla.org/Bug_Triage/Projects/Bug_Handling/Bug_Husbandry#Inactive_Bugs. If this bug is not an enhancement request or a bug not present in a supported release of Firefox, then it may be reopened.

Comment 4

[Oriol Brufau [:Oriol]]

This is not a bug not present in a supported release of Firefox, it's still reproducible on latest nightly 62. But only with e10s disabled, which I think is no longer supported, so I will leave the bug closed.

Comment 5

[Hiroyuki Ikezoe (:hiro)]

Oriol, thanks for the comment.  Your comment helped me to find this bug.  This bug will be opened within a few days (bug 1464312).

Anyway, I suspected this bug is somewhat related to bug 1459775.

Comment 6

[Hiroyuki Ikezoe (:hiro)]

I did try the step in comment 0 again and try to confirm what happens there.  I think this issue isn't related to bug 1459775 at all.  In this bug's case, when a link in the about:newtab is clicked, the docshell (I guess) starts loading the new link, at the moment, we don't discard the old layers (for about:newtab) at all.