1898338 - Update the checked state of moz-radio elements synchronously

Status: NEW

(Toolkit :: UI Widgets, task)

Description

[Hanna Jones [:hjones]]

As implemented in Bug 1894499 our moz-radio element's checked state only gets updated after its parent moz-radio-group element completes a render cycle. The current logic works like this:

1. a new moz-radio element is selected
2. moz-radio-group's value gets updated to the value of the selected moz-radio element
3. the value setter in moz-radio handles updating the checked state of each child moz-radio element
4. moz-radio's checked state is updated when the resulting render cycle completes

These kinds of asynchronous updates are expected for Lit-based components in general, but in this case it might be ideal to not have to wait for the related moz-button-group to update in order to know that the new checked state has propagated to all moz-radio elements. It should be possible to make these updates synchronous using requestUpdate and performUpdate.

Comment 1

[Simon Friedberger (:simonf)]

I'm not sure if it will actually help but Gijs pointed out that the code for the old XUL radio group is here: https://searchfox.org/mozilla-central/rev/eb80f267aabbf90ac66ebbed77b6d33592eb2be0/browser/components/preferences/main.js#2397-2402 and it also involves some disabling, awaiting and re-enabling.

Comment 2

[:Gijs (he/him)]

(In reply to Simon Friedberger (:simonf) from comment #1)

I'm not sure if it will actually help but Gijs pointed out that the code for the old XUL radio group is here: https://searchfox.org/mozilla-central/rev/eb80f267aabbf90ac66ebbed77b6d33592eb2be0/browser/components/preferences/main.js#2397-2402 and it also involves some disabling, awaiting and re-enabling.

There the consumer needs to wait for some other async operation before deciding what state they want to give the radio group. The issue Hanna described in comment 0 is that the propagation of the value property of the group to the checked state of the individual radio items is asynchronous (so the "internals" of foo.value = "some value" do not take effect synchronously). They are orthogonal issues. The setting of foo.value on XUL radiogroups is synchronous.