Antonio Scandurra
6639b4ff65
Fixes the hang introduced in #44995 (which was reverted in #45011) and re-enables the optimization. ## Background PR #44995 introduced an optimization to skip rendering lines that are clipped by parent containers (e.g., when a large AutoHeight editor is inside a scrollable List). This significantly improved performance for large diffs in the Agent Panel. However, #45011 reverted this change because it caused the main thread to hang for 100+ seconds in certain scenarios, requiring a force quit to recover. ## Root Cause The original analysis in #45011 suggested that visible_bounds wasn’t being intersected properly, but that was incorrect—the intersection via with_content_mask works correctly. The actual bug: when an editor is positioned above the visible viewport (e.g., scrolled past in a List), the clipping calculation produces a start_row that exceeds max_row: 1. Editor’s bounds.origin.y becomes very negative (e.g., -10000px) 2. After intersection, visible_bounds.origin.y is at the viewport top (e.g., 0) 3. clipped_top_in_lines = (0 - (-10000)) / line_height = huge number 4. start_row = huge number, but end_row is clamped to max_row 5. This creates an invalid range where start_row > end_row This caused two different failures depending on build mode: - Debug mode: Panic from subtraction overflow in Range<DisplayRow>::len() - Release mode: Integer wraparound causing blocks_in_range to enter an infinite loop (the 100+ second hang) ## Fix Simply clamp start_row to max_row, ensuring the row range is always valid: ```rs let start_row = cmp::min( DisplayRow((scroll_position.y + clipped_top_in_lines).floor() as u32), max_row, ); ``` ## Testing Added a regression test that draws an editor at y=-10000 to simulate an editor that’s been scrolled past in a List. This would panic in debug mode (and hang in release mode) before the fix. Release Notes: - Improved agent panel performance when rendering large diffs.
Zed
Welcome to Zed, a high-performance, multiplayer code editor from the creators of Atom and Tree-sitter.
Installation
On macOS, Linux, and Windows you can download Zed directly or install Zed via your local package manager (macOS/Linux/Windows).
Other platforms are not yet available:
- Web (tracking issue)
Developing Zed
- Building Zed for macOS
- Building Zed for Linux
- Building Zed for Windows
- Running Collaboration Locally
Contributing
See CONTRIBUTING.md for ways you can contribute to Zed.
Also... we're hiring! Check out our jobs page for open roles.
Licensing
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We use cargo-about to automatically comply with open source licenses. If CI is failing, check the following:
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no license specifiederror for a crate you've created? If so, addpublish = falseunder[package]in your crate's Cargo.toml. - Is the error
failed to satisfy license requirementsfor a dependency? If so, first determine what license the project has and whether this system is sufficient to comply with this license's requirements. If you're unsure, ask a lawyer. Once you've verified that this system is acceptable add the license's SPDX identifier to theacceptedarray inscript/licenses/zed-licenses.toml. - Is
cargo-aboutunable to find the license for a dependency? If so, add a clarification field at the end ofscript/licenses/zed-licenses.toml, as specified in the cargo-about book.