1795510 - Perspective property makes box-shadow render incorrectly (With sw-wr enabled)

Status: VERIFIED FIXED

(Core :: Graphics: WebRender, defect)

Description

[blendertut]

Attachment: image.png

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0

Steps to reproduce:

This markup:
<div class="parentt">

<div class="shadow">
<p>The shadow is broken".</p>
</div>
</div>

And this css:
.parentt{
perspective: 100rem;
}

.shadow {
width: 75%;
padding: 10px;

background-color: #fe5fe5;
        transition: all 2s ease;
        
box-shadow: 15px 15px 40px;
  transform: rotateY(75deg);

}

.shadow:hover{
transform: rotateY(180deg);
}

body {padding: 40px;}

Actual results:

Weird shadow effect, like it's rotating on the z axis instead of the Y.
Like so:
https://ibb.co/r4Qv66Q

Expected results:

Expected result is a normal shadow. Webkit has no problem with it.

This seems to be caused by the perspective property.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Web Painting' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 2

[Mayank Bansal]

Attachment: Reporters standalone testcase.html

Comment 3

[Mayank Bansal]

Attachment: software-WR VS hardware-WR.png

Comment 4

[Mayank Bansal]

cc rmader, in case we want hw-wr here instead of sw-wr.

Comment 5

[Mayank Bansal]

Hi blendertut,

Can you attach the content of about:support here?

Comment 6

[blendertut]

Attachment: AboutSupport

[quote]

Comment 7

[blendertut]

Here it is. Apparently this is caused by hardware acceleration? I indeed believe I have changed some settings in the past due to crappy nvidia drivers on linux. MIght be that?

Comment 8

[Robert Mader [:rmader]]

From what I understand you should be able to update to the 470 driver series (https://www.nvidia.com/Download/driverResults.aspx/191232/en-us/ - but Ubuntu should ship it) - can you try that?

Comment 9

[Jim Mathies [:jimm]]

Rendering quality issue with sw-wr? Might be core webrender as well, but it looks like accelerated is rendering properly. Could you set the right Severity here Lee?

Comment 10

[Lee Salzman [:lsalzman]]

Attachment: Bug 1795510 - Explicitly check for perspective in clip tile shaders for SWGL. r?aosmond

Clip tile shaders don't output the vertex W, so that SWGL can't detect if we're trying
to render something with perspective or not. swgl_drawSpan functions then get invoked
as if no perspective was used. In this case, we need to explicitly check to see if
there is perspective, or rather, that the W value varies along the span.

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d945b8d9c2e4
Explicitly check for perspective in clip tile shaders for SWGL. r=aosmond

Comment 12

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/d945b8d9c2e4

Comment 13

[Ardelean Oana, Desktop QA [:oardelean]]

Reproducible on a 2022-10-14 Nightly build on macOS 12 using the testcase from Comment 2.
Verified as fixed on Firefox 108.0b3(build ID: 20221117185908) and Nightly 109.0a1(build ID: 20221117214129) on macOS 12, Ubuntu 22, Windows 10.