1559076 - Maybe implement part forwarding.

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, enhancement, P3)

Description

[Emilio Cobos Álvarez (:emilio)]

https://drafts.csswg.org/css-shadow-parts/#exportparts-attr

There was no consensus on the specifics of this feature when it was being discussed.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1559076 - Implement shadow part forwarding (minus invalidation). r=heycam

Some of the stuff, in particular inside GeckoBindings stuff should be
refactored to be less ugly and duplicate a bit less code, but the rest of the
code should be landable as is.

Some invalidation changes are already needed because we weren't matching with
the right shadow host during invalidation (which made existing ::part() tests
fail).

Pending invalidation work:

• Making exportparts work right on the snapshots.
• Invalidating parts from descendant hosts.

They're not very hard but I need to think how to best implement it:

• Maybe get rid of ShadowRoot::mParts and just walk DOM descendants in the
  Shadow DOM.

• Maybe implement a ElementHasExportPartsAttr much like HasPartAttr and use
  that to keep the list of elements.

• Maybe invalidate :host and ::part() together in here1

• Maybe something else.

Opinions?

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1559076 - Minor debugging improvements. r=heycam

These were useful when implementing forwarding, and forgot to send them
earlier.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/ff37a98047d6
Minor debugging improvements. r=heycam

Comment 4

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/ff37a98047d6

Comment 5

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1559076 - Invalidate parts in nested shadow trees correctly. r=heycam

Comment 6

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1559076 - Restyle all descendants when the exportparts attribute changes. r=heycam

This attribute is not expected to change often, so it seems fine to restyle the
whole subtree.

Bug 1598094 tracks further optimizations, should they be needed.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/192393a2ffd3
Implement shadow part forwarding (minus invalidation). r=heycam

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/16c88ca27c45
Restyle all descendants when the exportparts attribute changes. r=heycam

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/08901de5eb94
Invalidate parts in nested shadow trees correctly. r=heycam

Comment 10

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/mozilla-central/rev/192393a2ffd3
https://hg.mozilla.org/mozilla-central/rev/16c88ca27c45
https://hg.mozilla.org/mozilla-central/rev/08901de5eb94