1921180 - Use `U+000A`(`LF`) instead of `<br>` when `contenteditable=plaintext-only` and the line breakers are preformatted by `white-space`

Status: RESOLVED FIXED

(Core :: DOM: Editor, defect)

Description

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

Chrome loves linefeed characters instead of <br> in contenteditable. Changing the behavior for contenteditable=true might be risky. I think that we should change our behavior only for contenteditable=plaintext-only first.

However, probably we need to change the behavior of inserting padding <br> for empty editor and last line since web apps do not assume linefeed and <br>s are mixed in same editing host.

Comment 1

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

Ah, textContent does not convert <br> to \n. So, it might be important to support this.

It seems that it's okay to use <br> for empty paragraph. It's same as Chrome and Safari. However, they delete the padding <br> at typing something. We should follow it.

Comment 2

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

Attachment: Bug 1921180 - part 1: Make `HTMLEditor` do not update nor join `Text` node if it has only one preformatted linefeed r=m_kato!

When inserting a preformatted linefeed, Chrome inserts a Text which has only
a linefeed instead of inserting the linefeed to existing Text. This allows
to keep Text smaller. So, let's follow the behavior.

Depends on D231663

Comment 3

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

Attachment: Bug 1921180 - part 2: Make `HTMLEditor::HandleInsertLinefeed` use `InsertLineBreak` with `LineBreakType::Linefeed` r=m_kato!

Depends on D231664

Comment 4

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

Attachment: Bug 1921180 - part 3: Make `HTMLEditor` use preformatted linefeeds if it's preferred r=m_kato!

Currently, only the "insert line break" handler uses a preformatted linefeed
instead of <br> if it's better. However, in contenteditable="plaintext-only", we should use preformatted linefeeds in most cases. Therefore, we should make them call the inserters with the GetPreferredLineBreak` result.

Depends on D231665

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3c5c29d73626
part 1: Make `HTMLEditor` do not update nor join `Text` node if it has only one preformatted linefeed r=m_kato
https://hg.mozilla.org/integration/autoland/rev/e2ea5020019f
part 2: Make `HTMLEditor::HandleInsertLinefeed` use `InsertLineBreak` with `LineBreakType::Linefeed` r=m_kato
https://hg.mozilla.org/integration/autoland/rev/f1683312c60f
part 3: Make `HTMLEditor` use preformatted linefeeds if it's preferred r=m_kato

Comment 6

[agoloman]

https://hg.mozilla.org/mozilla-central/rev/3c5c29d73626
https://hg.mozilla.org/mozilla-central/rev/e2ea5020019f
https://hg.mozilla.org/mozilla-central/rev/f1683312c60f