Bug 220576 – REGRESSION(r262893): feComponentTransfer is not rendered correctly on Retina display

• Status: RESOLVED
• Resolution: FIXED
• Component: SVG

[Xidorn Quan]

Created attachment 417504 [details]
testcase

Steps to reproduce:
1. open the testcase
2. click the "Set filter" button

Expected result:
The image becomes blurred.

Actual result:
The image is blurred, but also stretched a bit.

(I've observed even worse distortion when more complicated filters are added.)

I've tested Firefox and Chrome, and neither of them has this problem.

After some diagnose, I think this is because `feComponentTransfer` doesn't work correctly when the SVG is not somehow rendered. This behavior can be easily reproduced if the SVG element is `display: none`. (Note that Firefox shows nothing when SVG element is `display: none` though, not sure whose behavior is correct here.)

That makes me think that the distorted state being persisted is probably related to bug 99996 that even if the SVG element is correctly rendered, the filter result is not updated accordingly.

[Simon Fraser (smfr)]

The stretching seems to be related to Retina scaling (but only vertically?)

[Radar WebKit Bug Importer]

<rdar://problem/73160574>

[Said Abou-Hallawa]

Created attachment 418428 [details]
reduced test case

The stretching bug can occur with just static pages, i.e. no DOM change is needed to reproduce the bug.

[Said Abou-Hallawa]

This is a regression of r262893.

[Said Abou-Hallawa]

Created attachment 418673 [details]
more reduced test case

[Said Abou-Hallawa]

Created attachment 418688 [details]
Patch

[Simon Fraser (smfr)]

Comment on attachment 418688 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=418688&action=review

> LayoutTests/fast/hidpi/filters-component-transfer-expected.html:7
> +        filter: url("#a");

You can remove this here.

[Said Abou-Hallawa]

Created attachment 418699 [details]
Patch

[Said Abou-Hallawa]

Created attachment 418700 [details]
Patch

[EWS]

Committed r272059: <https://trac.webkit.org/changeset/272059>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 418700 [details].