Line Indent support is not common in certain languages

[t-hamano]

What problem does this address?

#73114 added support for text indentation. This support uses the p + p selector, so the first paragraph is skipped from the indent.

While this type of layout may be common practice in Western typesetting, it may not be the case in other languages.

For example, in Japanese, the first paragraph is never skipped. If indentation is used, it is common to add a one-character indent to every paragraph.

Additionally, Chinese uses a two-character indent, and the first paragraph does not appear to be skipped in this language either. cc @conanliuhuan

What is your proposed solution?

One approach I can think of is to allow the locale to decide whether to skip the first paragraph, like the word count type does. For example:

/**
 * translators: If the first paragraph should also be indented
 * (e.g. East Asian characters), set it to "include_first_paragraph".
 */
const textIndentType = _x( 'exclude_first_paragraph', 'Text indent type. Do not translate!' );
const textIndentSelector = textIndentType === 'exclude_first_paragraph' ? 'p + p' : 'p';

Or add an option to the UI to skip the first paragraph.

cc @mtias @aaronrobertshaw @ramonjd

[mako09]

Convention in Japanese Typography

The W3C's Requirements for Japanese Text Layout (JLReq) states in its preamble:

This document describes requirements for general Japanese layout realized with technologies like CSS, SVG and XSL-FO.

As shown in Figure 150, indentation is applied to all paragraphs. As explained in the sentence just before this figure:

a. Line head indent at the beginning of paragraphs is applied to all paragraphs. Nearly all books and magazines make use of this method (see Figure 150).

Nearly all books and magazines adopt this method.

(Note: This document also introduces the same method as English text afterward (Figure 154), but examples adopting this method are extremely rare.)

Thus, in Japanese documents, when we say "indent at the beginning of paragraphs," it is applied to all paragraphs without treating the first paragraph specially.

The current implementation contradicts this and should not be acceptable in Japanese, except in specially specified cases.

Imagine a situation where "indentation on all paragraphs including the first" is enforced. Many English-speaking readers would feel uncomfortable. The same thing is happening now. With the current implementation, many Japanese-speaking readers inevitably feel uncomfortable.

Does the author of each article have to pay attention to and configure the behavior of the first paragraph of each section? This will lead to inconsistencies due to oversight. No, it should be possible to set styles all at once elsewhere.

Chinese Example

Since I do not understand Chinese, I cannot state precise details. Here, I introduce an explanation of Chinese rules in Japanese.
According to this, the treatment of the first paragraph is probably the same as in Japanese.

Similar to JLReq, the W3C's Requirements for Chinese Text Layout exists (2023 draft). According to this:

1. Line head indent at the beginning of a paragraph is applied to all paragraphs. Nearly all books and magazines make use of this method.

The method of applying to all paragraphs is adopted in nearly all books and magazines.

Korean Example

Since I do not understand Korean, I cannot state precise details.

Similar to JLReq, the W3C's Requirements for Hangul Text Layout and Typography exists (2025 draft). According to this:

a. Line head indentations on every paragraph. The most common writing mode.

The method of applying to every paragraph is the most common.

According to the figure, indentation is also applied to the first paragraph.

Issues in English Contexts

In English contexts, the majority do not indent the first paragraph, but this does not mandate non-indentation. For example, The Chicago Manual of Style Q&A states that the first paragraph in a chapter or section "the indent isn't needed," but even though this is a convention, "they don't have to" follow it.

According to an article in Spanish, "both including and omitting the indentation on the first line of the first paragraph is perfectly valid."

Proposal

In other words, "both is valid" means both options need to be available. The current implementation forces exclusion of the first paragraph. This should basically be left to the site owner or designer.

[mako09]

One approach I can think of is to allow the locale to decide whether to skip the first paragraph, like the word count type does.

I don't think it's correct to have it fixed depending on the locale. It's important to have both options available in any locale, although it's fine to determine the default based on the locale.

[ramonjd]

It's important to have both options available in any locale, although it's fine to determine the default based on the locale.

I'd be wary of over complicating it. Would a toggle work (first line on/off) for most cases?

I mentioned the following over in #73114 (comment)

I can also imagine sites that are meant to be translated in both en and ja for example. For these cases, I think it should be up to the theme developer to apply theme automatically via using :lang(ja), :lang(zh), :lang(ko) to override behaviour

If we create defaults for one language we might fall down an i18n hole, where we have to start accommodating further locales in specific ways.

[ramonjd]

Would a toggle work (first line on/off) for most cases?

I just realized this might create headaches when replacing the p + p selector.

How would we apply a line indent in a logical way that doesn't affect paragraphs across the entire site? E.g.,

h1 + p,
h2 + p,
h3 + p,
.wp-block-heading + p {
  text-indent: 0;
}

[t-hamano]

Another headache comes when we have an image in the middle of a section. In this case, in the West, the paragraph after the image should be indented, right?

Furthermore, what if the sections are separated by separators?

Another concern is that the p or p + p selector affects elements that are not part of the sentence. For example, the comment form has three p elements lined up, which creates an unnatural indentation.

To fix this issue, we may need to add a class name to the Paragraph block. See #47282

[ramonjd]

Another headache comes when we have an image in the middle of a section. In this case, in the West, the paragraph after the image should be indented, right?

Yeah, I'm starting to agree with you: if there's no clean way to modify things as they exists, that a safe option could be to revert. #73114 (comment)

[t-hamano]

The main reason I'm suggesting reverting it is because it would be harder to make breaking changes to this feature if it were released as a Gutenberg plugin.

That said, I don't have an ideal idea yet 😅