1798614 - [CTW] Consider not caching opacity if it is 1.0

Status: RESOLVED FIXED

(Core :: Disability Access APIs, task)

Description

[James Teh [:Jamie]]

Opacity defaults to 1.0. Right now, we cache it for every Accessible except Accessibles that have no frame, even if it is 1.0. This wastes space in the cache for a value which will be the default for the vast majority of Accessibles.

The only Accessibles we cache that have no frame are display: contents. Even though display: contents is technically not visible itself, its contents are, so treating it as non-opaque seems semantically weird anyway.

I propose that we assume a default of 1.0 unless explicitly overridden.

Comment 1

[James Teh [:Jamie]]

Attachment: Bug 1798614: Assume a default of 1.0 for Accessible::Opacity unless otherwise explicitly specified.

Previously, it was possible to have no value, but only for Accessibles without frames.
That effectively means display: contents, and since the content is visible (even though the element itself doesn't have a box), exposing it as non-opaque isn't important and arguably doesn't make sense.
This way, we avoid awastefully caching 1.0 for the vast majority of Accessibles.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/55c67f7c005b
Assume a default of 1.0 for Accessible::Opacity unless otherwise explicitly specified. r=morgan,eeejay

Comment 3

[James Teh [:Jamie]]

Attachment: Bug 1798614 follow-up: Don't send DeleteEntry on initial cache updates for opacity and table cell headers.

The primary intent of the first patch here was to avoid memory wasted by caching default opacity values.
Unfortunately, this was defeated by the fact that we previously sent DeleteEntry for initial cache updates of opacity.
This resulted in DeleteEntry being stored in the parent process cache, since DeleteEntry is only handled specially for cache updates, not initial pushes.
We now only send DeleteEntry for cache updates, which is consistent with what we do for other cache attributes.
While fixing this, I discovered that we made the same mistake for table cell headers, so I fixed that as well.

Comment 4

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/55c67f7c005b

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5ede79a3d867
follow-up: Don't send DeleteEntry on initial cache updates for opacity and table cell headers. r=morgan

Comment 6

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/5ede79a3d867