tab_switcher: Middle-truncate long picker filenames

[saberoueslati]

Context

This follow-up was inspired by Christopher’s suggestion in the review comment on #58483: long filenames should truncate in the middle so both the beginning and the suffix/extension remain visible.

Previously, very long filenames in picker rows could still be clipped or end-truncated, making files with shared prefixes hard to distinguish. This adds middle-truncation support to GPUI text overflow and applies it to filename-focused picker surfaces: the tab switcher and the Ctrl-P file finder. Normal editor tab bar behavior remains unchanged and continues to use the existing title length cap.

How to Review

• crates/gpui/src/style.rs, crates/gpui/src/styled.rs, crates/gpui/src/elements/text.rs, crates/gpui/src/text_system/line_wrapper.rs: Adds TextOverflow::TruncateMiddle, wires it through text layout, and implements middle truncation while preserving valid text runs. Very narrow widths now show the truncation affix instead of falling back to the abruptly clipped original text.

• crates/ui/src/components/label/label_like.rs, crates/ui/src/components/label/label.rs, crates/ui/src/components/label/highlighted_label.rs: Exposes middle truncation through the shared label components.

• crates/workspace/src/item.rs, crates/editor/src/items.rs, crates/workspace/src/pane.rs, crates/tab_switcher/src/tab_switcher.rs: Adds an explicit tab-content opt-in for middle truncation. The tab switcher enables it, while the normal tab bar and dragged tabs keep their existing behavior.

• crates/file_finder/src/file_finder.rs: Applies middle truncation to Ctrl-P file finder filenames and lets the path shrink from the start so long paths do not hide important filename suffixes.

Manual test before change :

Screencast.from.2026-06-10.22-59-28.webm

Manual test after change :

Screencast.from.2026-06-10.22-54-48.webm

Self-Review Checklist

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Release Notes:

• Improved long filename truncation in the tab switcher and file finder so extensions remain visible.

[ChristopherBiscardi]

Very cool, thanks for taking this on!

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This definitely doesn't handle unicode codepoints correctly but notably it doesn't seem like any of the other already-existing truncation code does either, so I'm not going to consider it a blocker for this PR.

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For the unicode issue, consider the following polar bear, which is the combination of a bear, a zero-width-joiner, and a snowflake.

aaaa🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️🐻‍❄️bbbbbbb.txt

When truncated, this splits the middle and results in each side of the emoji rendering.

[moechofe]

So, now the filename is truncated even if there is enough space for the name to be display entirely.
Doesn't seems to be the right move. IMHO

In this example, the file is MBKong.hpp, and g.h was removed.
In the changelog, it says: "... so extensions remain visible", but it's not true.