1919927 - Implement `contenteditable=plaintext-only` outside the editor module

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, task)

Description

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

First, we need a pref to enable it and new (optional) handler of contenteditable attribute changes under dom/.

Comment 1

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Attachment: Bug 1919927 - Implement `contenteditable="plaintext-only"` in the DOM module r=smaug!

It requires a lot of changes in the editor module, and the layout module may
need read-write-plaintext-only and user-modify: read-write-plaintext-only.
When we work on the modules, we need the basic support under dom/. This
patch adds plaintext-only support only when the new pref is enabled.

Once the pref is enabled, the following failures will be fixed:

• https://searchfox.org/mozilla-central/rev/f2c181a7ab3bfea4d2266521e6eac713630479b3/testing/web-platform/meta/html/editing/editing-0/contenteditable/contenteditable-enumerated-ascii-case-insensitive.html.ini#4-5,7-8,10-11,13-14
• https://searchfox.org/mozilla-central/rev/f2c181a7ab3bfea4d2266521e6eac713630479b3/testing/web-platform/meta/html/editing/editing-0/contenteditable/user-interaction-editing-contenteditable.html.ini#4-5,7-8

FYI: Element::IsContentEditablePlainTextOnly() is useful for HTMLEditor
to check whether active editing host is so or not. Therefore, I'd like to
add it even though there is no user of it.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0f470e1a67af
Implement `contenteditable="plaintext-only"` in the DOM module r=smaug

Comment 3

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/0f470e1a67af