1554753 - Emoji do not respect 0% opacity when combined with drop shadow

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect, P3)

Description

[Terence Eden]

Attachment: Invisible Pink Unicorns - a Firefox rendering bug.png

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:67.0) Gecko/20100101 Firefox/67.0

Steps to reproduce:

This pink unicorn should be invisible.

<span style="font-size:3em;color: rgba(255, 105, 180, 0.0); text-shadow: .2em .2em .2em #000;
">🦄 Unicorn</span>

Actual results:

The Unicorn has 100% opacity, but the text has 0% opacity.

Expected results:

The unicorn should also be invisible.

The only way on Firefox, to get a completely invisible pink unicorn plus a drop shadow is to use: color: rgba(255, 105, 180, 0.002); text-shadow: .2em .2em .2em #000;

If you use: rgba(255, 105, 180, 0.001); the Unicorn becomes visible again.

This only appears to be a problem on FF for Linux. It works on FF for Android.

Comment 1

[Alice0775 White]

Attachment: Bug 1554753 - Emoji do not respect 0% opacity when combined with drop shadow.html

Regression window:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=3ae9a6bb08211560f6c27a362de4243e676266e9&tochange=5f3ba1d0bbf4cbfe14050cf230c289fc71bb5ab3

Regressed by: Bug 1248708

Comment 2

[BugBot [:suhaib / :marco]]

The priority flag is not set for this bug.
:dholbert, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 3

[violet.bugreport]

The difference between 0.002 and 0.001 is simply a rounding problem, because 256 * 0.002 > 0.5 rounded to 1, while 256 * 0.001 < 0.5 thus rounded to 0.

Comment 4

[violet.bugreport]

Attachment: Bug 1554753 - Should not treat 0 opacity text without stroke width as drawing stroke

The regressor Bug 1248708 inadvertently changed the behavior for opacity 0 text
when implementing -webkit-text-stroke. It treats all opacity 0 text as drawing stroke
even if the stroke property isn't used in the first place.

We should check aParams.textStrokeWidth is actually set before changing draw mode.

Comment 5

[Daniel Holbert [:dholbert]]

Thanks for jumping on this, Violet!

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/362cff551a01
Should not treat 0 opacity text without stroke width as drawing stroke r=jfkthame

Comment 7

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/362cff551a01

Comment 8

[Ryan VanderMeulen [:RyanVM]]

This seems edge-case enough that it can ride the trains. Can we add a test for it, though?

Comment 9

[violet.bugreport]

A testcase is difficult for this bug, see discussion https://phabricator.services.mozilla.com/D34663#1029466