1225372 - [Mac] -moz-linear-gradient renders slightly differently if I specify "0%" & "100%" explicitly on color stops

Status: NEW

(Core :: Graphics, defect, P3)

Description

[Daniel Holbert [:dholbert]]

-moz-linear-gradient renders differently on Mac, depending on whether I let the color stop positions be implied, vs. if I specify them explicitly (0% / 100%).

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: reftest patch to demonstrate this bug (on mac)

Try run which I believe will have some reftest orange due to this bug, based on an earlier slightly-more complex Try run:
  https://treeherder.mozilla.org/#/jobs?repo=try&revision=9afa3b8dbb69

I'm attaching the patch from that Try run, for reference. It just adds a testcase & a reference case, which only differ by the presence or absence of "0%" and "100%" after the color stops in the gradient expression.

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: reftest log snippet from try run

(Here's the relevant reftest log snippet from the Mac reftest failures in comment 1's Try run.)

Comment 3

[Daniel Holbert [:dholbert]]

The reftest log starts with:
REFTEST TEST-UNEXPECTED-FAIL | file:///builds/slave/test/build/tests/reftest/tests/layout/reftests/bugs/mac-gradient-test-1.html | image comparison (==), max difference: 3, number of differing pixels: 2136

So, adding explicit "0%" / "100%" to the gradient color-stops *very subtly* changes the majority of the gradient area in this testcase, for some reason. (And only on Mac).

Comment 4

[Daniel Holbert [:dholbert]]

(This might be a OS X 10.6-specific bug. At least, I can't reproduce locally on my Mac Mini which is running OS X 10.10.5.)

Comment 5

[Daniel Holbert [:dholbert]]

Nope, this isn't 10.6-specific. It reproduces on our TreeHerder 10.10 boxes:
  https://treeherder.mozilla.org/#/jobs?repo=try&revision=134ad1d2b18d

Not sure what's special about them as compared to my mac mini. Anyway, I'm not worrying about this too much, given that it's visually-imperceptible and I can't seem to investigate locally.