1794096 - [COLRv1] Incorrect linear gradient interpolation for pad and color stop range 0

Status: RESOLVED FIXED

(Core :: Graphics: Text, defect)

Description

[Dominik Röttsches (drott)]

Attachment: offset_50.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

Steps to reproduce:

Visit:
https://roettsch.es/var_colrv1.html?filter=extend_mode for

And paste:
offset=51; COL3.value=50+offset; COL2.value=100+offset;COL1.value=150+offset; updateAll();

Then paste:
offset=50; COL3.value=50+offset; COL2.value=100+offset;COL1.value=150+offset; updateAll();

and compare results.

Actual results:

For offset=50, the red green divide in the first linear gradient glyph jumps back left, even though it should almost be the same as 51.

Expected results:

Red green divide should stay in almost the same spot.

I suspect the projection is skipped due to the color line range becoming 0.

Comment 1

[Dominik Röttsches (drott)]

Attachment: offset_51.png

Comment 2

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1794096 - Fix the rendering of padded linear gradient when the color line is zero-length. r=lsalzman

This is the linear-gradient version of bug 1793611 for radial gradients, and is fixed similarly.
Includes reftest.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ad2fbcab86cb
Fix the rendering of padded linear gradient when the color line is zero-length. r=lsalzman

Comment 4

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/ad2fbcab86cb