[audit] multi-cursor: vertical arrow keys use document-order traversal instead of visual movement

[claude]

Problem

In src/plugins/multiCursor/inputHandling.ts (lines 194–226), the ArrowUp/ArrowDown handler for multi-cursor mode uses Selection.findFrom($head, dir, true) to find the target position. This is a document-order operation that searches for the nearest valid text selection position, not a visual/coordinate-based vertical movement.

For single-line paragraphs, this works fine (it jumps to the adjacent block). But for long paragraphs with soft line wrapping, ArrowDown will not move to the line below visually — it will either find nothing or jump to the next textblock boundary.

In contrast, the addCursorAbove/addCursorBelow commands in commands.ts correctly use view.coordsAtPos/view.posAtCoords for coordinate-based vertical placement. The difference is that handleMultiCursorArrow only receives state (not view), so it cannot use coordinate-based movement.

Impact

ArrowUp/ArrowDown in multi-cursor mode behaves incorrectly in wrapped text — cursors jump between textblocks rather than moving visually up/down within a wrapped paragraph. This is inconsistent with normal ProseMirror vertical arrow behavior, which delegates to the browser's native caret movement.

Suggested fix

Either:

1. Pass EditorView through to handleMultiCursorArrow so it can use coordinate-based movement (like addCursorVertical does), or
2. Handle vertical arrow keys at the view level (in handleKeyDown plugin) where the view is available, rather than routing through the state-only handleMultiCursorArrow

File: src/plugins/multiCursor/inputHandling.ts:194-226

[xiaolai]

Fixed in 464a96a.

Added optional view?: EditorView parameter to handleMultiCursorArrow and handleMultiCursorKeyDown. When the view is available and the movement is vertical (ArrowUp/ArrowDown), the handler now uses coordinate-based placement via view.coordsAtPos() / view.posAtCoords() — mirroring the approach in addCursorVertical from commands.ts.

Falls back to document-order Selection.findFrom() when the view is not available (e.g., in tests without a DOM). The plugin passes the view through from multiCursorPlugin.ts.