1671890 - CSS filter blur on wrong area when element cropped by overflow hidden

Status: RESOLVED WORKSFORME

(Core :: Graphics: WebRender, defect)

Description

[mmis1000]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:83.0) Gecko/20100101 Firefox/83.0

Steps to reproduce:

1. add a big element that largely overflow a fill page container in all direction with position absolute.
2. apply small blur on it.
3. add overflow hidden to parent container

<div class="out">
  <div class="in">
    A
  </div>
</div>

.out {
  position: fixed;
  top: 0px;
  left: 0px;
  right: 0px;
  bottom: 0px;
  overflow: hidden;
}

.in {
      background-image: url("http://via.placeholder.com/400x100/000070/FFFFFF/?text=Test");
  background-size: cover;
  position: absolute;
  background-position: center;
  top: -10px;
  left: -10px;
  right: -10px;
  bottom: -10px;
  filter: blur(5px);
}

firefox: https://i.imgur.com/V2LOETx.jpg
chrome: https://i.imgur.com/bQ2X6Hu.jpg

Actual results:

The cropped element have white blur at border even that should be out of viewport.

Seems the blur was apply after crop instead of before crop.

Expected results:

The cropped element don't have white blur at border because that was cropped (just like chrome)

Comment 1

[Jeff Muizelaar [:jrmuizel]]

Attachment: Testcase

Comment 2

[mmis1000]

Note: this is a regression, does not happen on firefox 80

Comment 3

[Alice0775 White]

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=25a50264ae3204f2df9add308fc712df45947637&tochange=c8102686489e51edec8a976f013398412577be44

Comment 4

[mmis1000]

Looks this may be a duplicate of bug Bug 1661147 .
Not sure whether they a regressed by the same commit.

Comment 5

[Glenn Watson [:gw]]

This seems to be fixed for me in current nightly - could you verify?

Comment 6

[mmis1000]

(In reply to Glenn Watson [:gw] from comment #5)

This seems to be fixed for me in current nightly - could you verify?

I seems work incorrectly when opening the devtool for some reason.
Work if the devtool not opned.

Comment 7

[Glenn Watson [:gw]]

This is working for me, both in normal mode and also with devtools open. It's likely it was fixed as part of the changes in bug #1749380.

Please re-open if you can still reproduce.