1778899 - Setting `filter: drop-shadow()` on an element causes its background color to shift if it has an partial alpha value

Status: RESOLVED INVALID

(Core :: CSS Parsing and Computation, defect)

Description

[Itiel]

STR:

1. Open https://jsitor.com/beg0dq3xR-
2. Hover the Google logo, see its background color
3. Toggle the filter: drop-shadow() off and hover the Google logo again

AR:
See that the background color is different.

ER:
I would expect the background color to remain the same, but in Chrome I can see the same result (with setting RGBA instead, as they don't support color-mix() atm) as in Firefox.

Comment 1

[Alice0775 White]

#1 Regression window:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=c7e489f5759a6dc1e0dabdab8772339410e5e12b&tochange=46580fa5a4ce20c8cf1c7c9f3f520a1e9c644518

Triggered by : Bug 1695376

#2 Progression window:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=8f05e804fa6a40e6407cfc604008c3fb66013c77&tochange=95b6c826ad974a967364cb1f137bd8a766051d0a
Progressed : Bug 1696434

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Attachment: Reduced test-case.

Comment 3

[Emilio Cobos Álvarez (:emilio)]

This is much more obvious when the drop shadow is not black-ish. The background color is an input to the shadow, so it's expected to be darker.