fix: restore mouse wheel scrolling in the review screens

[benglewis]

The regression

Scrolling with the keyboard works; the mouse wheel does nothing. It used to work before #119.

#119 added no mouse handling either way — what changed is that ScrollableViewport clips the content to the window (height + overflow: hidden). Before that, long reviews overflowed into the terminal's scrollback, and the wheel scrolled that natively. Now nothing reaches the scrollback, so the wheel scrolls an empty buffer and looks dead.

The fix

A terminal only reports the mouse to an application that asks for it, so ask — and read the wheel back.

• src/lib/input/mouse.ts — turn tracking on (?1000 + SGR ?1006) and parse wheel reports, in both the SGR and legacy encodings, ignoring clicks, drags, the horizontal wheel, and any modifiers held while scrolling.
• src/hooks/useMouseWheel.ts — asks for the mouse while active (ref-counted across viewports, restored on exit) and delivers wheel events.
• ScrollableViewport — a notch scrolls three lines, matching what terminals do themselves.

Mouse reporting is asked for only while there is something to scroll, because it costs something: with it on, the terminal hands clicks to the application instead of using them for text selection. Off the moment the content fits.

Two things found along the way, both fixed here:

• A zero-row viewport counted as scrollable (maxOffset > 0 while viewportHeight === 0), so the scroll keys were live on content no one could see. Now gated on the viewport having rows.
• A legacy ESC [ M report packs three raw bytes that are not parameter characters, so the tokenizer would have split them out as text and typed them into the search box. Read as one sequence now.

Testing

npm run cicd — lint, format, 99 tests, build, all clean.

• src/lib/input/mouse.spec.ts — 8 cases over both encodings, modifiers, clicks/drags/horizontal wheel, releases and ordinary keys.
• src/components/ScrollableViewport.spec.tsx — wheel scrolls three lines and back, stops at both ends, asks for the mouse and hands it back on unmount, and leaves it alone when there is nothing to scroll.
• src/lib/input/line-editor.spec.ts — a legacy report stays one token and inserts nothing.

Verified in the built output driven through a real pty, not just in tests:

asked terminal for mouse reporting: True
top line at rest:            line 0
top line after wheel down:   line 3
status after wheel down:     ↑↓ lines 4-19 of 40 · ↑/↓ PgUp/PgDn to scroll
top line after 2nd down:     line 6
top line after wheel up:     line 3
released mouse on exit:      True

Branch is cut from main at 9caa378.

🤖 Generated with Claude Code

[baz-reviewer]

Baz Summary

Restore mouse-wheel scrolling in clipped review viewports by enabling terminal mouse reporting and parsing SGR and legacy wheel events. Update ScrollableViewport, useMouseWheel, and input tokenization to deliver three-line wheel scrolling without capturing clicks when content cannot scroll.

Topics

Topic	Details
Input and documentation	Prevent legacy mouse reports from being tokenized as typed text and document the new wheel behavior and terminal interaction. Modified files (3) README.md src/lib/input/line-editor.spec.ts src/lib/input/line-editor.ts Latest Contributors(0) User Commit Date
Mouse wheel scrolling	Restore wheel scrolling in review screens by tracking terminal mouse input only while content overflows, handling viewport ownership and three-line movement, and releasing tracking on cleanup. Modified files (5) src/components/ScrollableViewport.spec.tsx src/components/ScrollableViewport.tsx src/hooks/useMouseWheel.ts src/lib/input/mouse.spec.ts src/lib/input/mouse.ts Latest Contributors(0) User Commit Date

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