feat(web): faster drag autoscroll and richer terminal selection

[westwol]

Dragging a selection past the edge of the terminal scrolled at a fixed 1 row per 80ms regardless of how far past the edge the pointer went, so selecting a screenful of scrollback meant holding still for several seconds. Selection was also mouse-only: no select all, no block selection, no keyboard selection.

The autoscroll rate is now driven by how far past the edge the pointer sits, integrated over real elapsed time on rAF rather than a fixed interval — a slight overhang still creeps for fine control, while a long drag covers pages per second. It also skips the re-extension and its full repaint once scrollback hits either end, where the old loop repainted every frame while moving nothing.

Selection gained four capabilities, each built on a libghostty-vt primitive that was already vendored but unused:

• Select all — Cmd+A, Ctrl+Shift+A off mac, plus a context menu entry. A bare Ctrl+A stays with the shell, since it is readline's beginning-of-line and tmux's default prefix.
• Block selection — Alt+drag, via the rectangle flag on Ghostty's selection struct.
• Keyboard selection — Shift+Arrows/Home/End/PageUp/PageDown, extending from the cursor and scrolling the moving end into view. Gated off on the alternate screen and under mouse tracking so vim, htop and friends keep their own shifted chords.
• Select command output — needs OSC 133 marks from the shell. The server spawns $SHELL without injecting shell integration, so the entry is probed per right-click and omitted entirely when the shell emits no marks, rather than offering an action that silently does nothing.

Verification

61 unit tests pass across the new pure helpers (autoscroll rate, overshoot, keyboard move/target, the select-all shortcut, context menu composition); typecheck and lint are clean on all five files.

runtimeAbi.test.ts — the only test that exercises the real WASM — cannot collect locally due to a pre-existing .wasm?inline import-analysis issue, confirmed present on a clean tree. So the three WASM-touching paths were verified with standalone probes against the vendored ghostty-vt.wasm:

• Block selection over ABCDEFGH/IJKLMNOP/QRSTUVWX from (2,0) to (4,2) yields CDE / KLM / STU, versus CDEFGH / IJKLMNOP / QRSTU for flow selection.
• select_output returns exactly the command's output with OSC 133 marks present, and error -4 without them or on a prompt line.
• select_all returns usable screen bounds for anchoring the copy affordance.

Outstanding

AGENTS.md asks for a short video on motion or timing changes. The autoscroll change is exactly that, and no clip is attached here — it needs a real browser session to capture. Happy to add one before merge.

Screen.Recording.2026-08-17.at.2.13.36.a.m.mov

Written by Claude Opus 5 (1M context) via Claude Code.

🤖 Generated with Claude Code

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Note

Medium Risk
Touches core terminal input/selection and WASM APIs with shell shortcut conflicts mitigated by gating, but behavior is user-visible and easy to regress in vim/tmux or unmarked shells.

Overview
Improves terminal selection and scroll behavior on the Ghostty canvas terminal in the thread drawer.

Drag autoscroll replaces the fixed-interval ±1-row timer with rAF-driven scrolling whose speed scales with how far the pointer overshoots the grid edge; it skips useless repaints when scrollback is already at an end.

New selection capabilities wire through GhosttyTerminalCore / GhosttyTerminalSurface: Select all (Cmd+A / Ctrl+Shift+A, context menu), Alt+drag block selection (rectangle on setSelection), Shift+arrow/Home/End/Page keyboard extension (disabled on alternate screen and mouse tracking), and Select command output when OSC 133 marks exist—captured at right-click time with a buffer generation guard so async menus do not apply stale ranges.

Context menu in ThreadTerminalDrawer always offers Select all and Paste; copy/add-to-chat stay disabled without a selection; select-output appears only when a bounded output range is under the pointer.

Session buffer sync stops clearing selection on every append (Ghostty keeps selections pinned); full buffer replaces still reset selection via resetAndWrite.

^{Reviewed by Cursor Bugbot for commit f24d700. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Add rectangular selection, keyboard selection, and distance-based autoscroll to terminal

• Adds Alt+drag rectangular (block) selection and Cmd+A/Ctrl+Shift+A select-all to GhosttyTerminalSurface, with scrollback included and viewport position preserved.
• Adds Shift+Arrow/Page/Home/End keyboard-driven selection extension when not in alternate screen or mouse tracking mode.
• Replaces the setInterval-based autoscroll with a requestAnimationFrame integrator using distance-proportional rows-per-second, capping speed for throttled tabs.
• Adds a "Select command output" context menu item that appears when right-clicking over bounded command output, using a generation stamp to guard against stale selections after buffer replacements.
• Behavioral Change: selection is no longer cleared on terminal append writes; buffer replacements clear selection via buffer reset instead.

^{Macroscope summarized f24d700.}

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Approvability

Verdict: Needs human review

This PR introduces substantial new terminal selection features (Select All, command output selection, keyboard selection, block selection, improved autoscroll). While well-tested and authored by the primary maintainer of these files, the scope of new user-facing behavior warrants human review.

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Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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