| Baselines, Myers line diffs, debouncing, undo/redo, and the edge cases behind SavePoint Diff's gutter markers.

I recently shipped SavePoint Diff , a VS Code extension that shows gutter markers for unsaved changes. Here's the design, in case you're thinking about building something similar.

The core idea: a baseline

Everything revolves around one string per file, the baseline , meaning the last saved content.

File opens: capture its content as the baseline.

Edit: diff baseline against the current buffer, then render the result as gutter decorations.

Save: the baseline becomes the new content, and the markers clear.

The diff itself uses a small, well-established Myers line-diff library rather than anything custom.

Debouncing

Diffing on every keystroke is wasteful, so recalculation is delayed until typing pauses.…