editor: Fix Git blame gutter width with avatars

[lingyaochu]

Objective

When using column Git blame with avatars enabled, blame entries whose author name is the longest in the buffer can exceed the blame border.

For example, line 10 of crates/vim/src/visual.rs is displayed as follows:

The blame contents exceeds the width.

The root cause is in the blame width calculation:

zed/crates/editor/src/editor.rs

Lines 11583 to 11598 in 0c51c7f

	let git_blame_entries_width =
	self.git_blame_gutter_max_author_length
	.map(|max_author_length| {
	let renderer = cx.global::<GlobalBlameRenderer>().0.clone();
	const MAX_RELATIVE_TIMESTAMP: &str = "2 years, 11 months ago";
	/// The number of characters to dedicate to gaps and margins.
	const SPACING_WIDTH: usize = 4;
	let max_char_count = max_author_length.min(renderer.max_author_length())
	+ ::git::SHORT_SHA_LENGTH
	+ MAX_RELATIVE_TIMESTAMP.len()
	+ SPACING_WIDTH;
	ch_advance * max_char_count
	});

The calculation accounts for the commit SHA, author name, and timestamp. Other elements, including spacing, margins, and the avatar, are represented by the fixed SPACING_WIDTH constant.

For typical fonts, ch_advance is approximately 0.5rem to 0.6rem, so SPACING_WIDTH provides approximately 2rem to 2.4rem for non-text content. However, the avatar itself occupies 1rem:

zed/crates/ui/src/components/avatar.rs

Line 81 in 0c51c7f

let image_size = self.size.unwrap_or_else(|| rems(1.).into());

When avatars are displayed, the entry also contains three 0.5rem gaps and also one 0.5rem right margin:

zed/crates/git_ui/src/blame_ui.rs

Lines 170 to 188 in 0c51c7f

	div()
	.mr_2()
	.child(
	h_flex()
	.id(("blame", ix))
	.w_full()
	.gap_2()
	.justify_between()
	.font(style.font())
	.line_height(style.line_height)
	.text_color(cx.theme().status().hint)
	.child(
	h_flex()
	.gap_2()
	.child(div().text_color(sha_color).child(short_commit_id))
	.children(avatar)
	.child(name),
	)
	.child(relative_timestamp)

This requires approximately 3.0rem, which can exceed the space provided by SPACING_WIDTH. When an entry contains both the longest author name in the buffer and a long timestamp, its content can therefore exceed the blame border.

Solution

The simplest fix would be to increase SPACING_WIDTH, but that would still rely on an approximate conversion between editor character widths and UI dimensions.

Instead, this PR adds a method to the blame renderer for calculating the non-text width of a blame entry. The editor uses this value together with the measured text width when calculating the final blame width.

Testing

Tested locally. A before-and-after comparison is included below.

Self-Review Checklist:

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

Showcase

Before	After

Release Notes:

• Fixed Git blame entries overflowing the gutter when avatars are displayed.

[ChristopherBiscardi]

thanks!