[css-display] Do empty text nodes generate text runs?

[Loirooriol]

Do text nodes with an empty string value generate a text run or not?

The difference will affect run-in layout:

If a run-in sequence is immediately followed by a block box [...]

And it's also observable in flow layout. According to CSS 2.2,

Line boxes that contain no text [...] must be treated as not existing [...]

I guess "text" refers to text runs. See https://jsfiddle.net/rs94bpay/

<div><div>Foo</div></div>

div {
  white-space: pre;
  border: 1px solid blue;
}

document.querySelector('div').prepend('');

Firefox does not discard the line because of the text node, Chrome and Edge do.

[SelenIT]

The behavior of Firefox looks like a bug. The script doesn't add any white space characters that should be taken into account by white-space property. Interestingly, the same issue occurs for body > div::before { content: '' } instead of prepending empty string with the script.

[fantasai]

That's super weird, and it's definitely a bug. Different DOMs that output the same source code should not result in different CSS output, ever.

@SelenIT ::before { content: '' } is a little different, it causes the ::before pseudo-element to exist, and empty inline boxes count as content that causes a line box to exist.

[SelenIT]

empty inline boxes count as content that causes a line box to exist

They do, but shouldn't they be treated as "not existing for any other [than positioning out-of-flow descendants] purpose" phantom line boxes?

[Loirooriol]

@fantasai If I understand correctly, you mean that

• An empty text node generates no text run.
• A ::before or ::after with content: '' generates an empty text run.

Is that correct?

[fantasai]

@Loirooriol A ::before or ::after with content: '' generates a box containing nothing.

[fantasai]

@SelenIT That depends on if they are assigned any other styles. :)