compound emojis do not render correctly in buffer

[teidesu]

Reproduction steps

1. try pasting 😭🙏🏳️‍🌈👩‍🏫🫱🏾‍🫲🏻🇺🇸 in the editor
2. note how compound emojis are rendered as separate emojis (yet skin tones are applied correctly)

Current vs. Expected behavior

current behavior:

with the default font:

with iosevka:

adding "buffer_font_fallbacks": ["Apple Color Emoji"], doesn't change anything, setting "buffer_font_family": ".SystemUIFont" doesn't help either

interesting that caret and selection works per actual emoji and not per rendered glyph:

Screen.Recording.2025-12-21.at.02.04.23.mov

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might be related to #15925, but im not entirely sure it's the same issue, since that issue seems to affect any emoji rendering on linux and here it works fine except zwj emojis

Zed version and system specs

Zed: v0.217.3+stable.105.80433cb239e868271457ac376673a5f75bc4adb1 (Zed)
OS: macOS 15.6.1
Memory: 36 GiB
Architecture: aarch64

Attach Zed log file

Zed.log

Relevant Zed settings

settings.json

Relevant Keymap

keymap.json

(for AI issues) Model provider details

No response

If you are using WSL on Windows, what flavor of Linux are you using?

None

[SomeoneToIgnore]

Nice catch, thank you.
Given that the tab text renders fine, I've reverted #43080 and see the correct results now:

The PR is "correct" though and should not be reverted per se, but the logic for splitting the font runs into logical chunks is flawed — those are separated now based on the highlights, whilst in reality should consider the compounds too:

zed/crates/editor/src/display_map.rs

Lines 1172 to 1186 in a5540a0

	let mut runs = Vec::new();
	let mut line = String::new();
	let range = display_row..display_row.next_row();
	for chunk in self.highlighted_chunks(range, false, editor_style) {
	line.push_str(chunk.text);
	let text_style = if let Some(style) = chunk.style {
	Cow::Owned(editor_style.text.clone().highlight(style))
	} else {
	Cow::Borrowed(&editor_style.text)
	};
	runs.push(text_style.to_run(chunk.text.len()))
	}