1479230 - Remove useless condition in GetPrefersReducedMotion.

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, enhancement)

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1479230: Remove useless condition in GetPrefersReducedMotion. r=hiro

This query is always enabled in content, so this check is always true.

The early return (similar to the return in the switch clause) makes me a bit
uncomfortable btw. Returning without changing a value makes the query
unconditionally evaluate to false. Which means that pages that detect the query
at runtime like:

  @media (prefers-reduced-motion: no-preference) {
    do-animations
  }

  @media (prefers-reduced-motion) {
    dont-do-animations
  }

Or something of the sort will be broken... Probably not a huge concern since
it's unlikely, but was this considered? Should we just return NoPreference for
unsupported platforms / resist fingerprinting?

Comment 2

[Phabricator Automation]

Comment on attachment 8995759 [details]
Bug 1479230: Remove useless condition in GetPrefersReducedMotion. r=hiro

Hiroyuki Ikezoe (:hiro) has approved the revision.

https://phabricator.services.mozilla.com/D2490

Comment 3

[Emilio Cobos Álvarez (:emilio)]

Thanks for the review Hiro! Any opinion on comment 1? I'll remove that from the commit message, but I want to confirm the current behavior is intentional.

Comment 4

[Hiroyuki Ikezoe (:hiro)]

It's not intentional, I have no idea how happens the situation.  That's said, I agree clearing |aResult| and setting NoPreference looks safer actually.  Feel free to do that!

Comment 5

[Emilio Cobos Álvarez (:emilio)]

I'll file a bug, since that's a change in behavior and we have a good way to test it via the resistFingerPrinting pref.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/dc5ea0cbf005
Remove useless condition in GetPrefersReducedMotion. r=hiro

Comment 7

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/dc5ea0cbf005