Live cursors

Problem Context

• Users are co-editing a document, design canvas, slide, diagram, whiteboard, code editor, map, media timeline, spreadsheet, or shared object where spatial attention matters.
• Remote signals may include mouse pointer, touch pointer, text caret, selected object, selection range, viewport focus, temporary cursor chat, and follow-mode target.
• Cursor data changes quickly, may lag or drop during network issues, and should usually remain outside durable document history.
• The surface may have many collaborators, anonymous viewers, external guests, private regions, presentation mode, mobile touch input, or assistive technology users.

Selection Rules

• Choose live cursors when users need immediate spatial awareness of other collaborators' current pointer, caret, selection, viewport, or focus inside the same shared surface.
• Use presence when the user only needs to know who is available, online, viewing, away, or recently active, not exactly where they are pointing.
• Use comments when feedback must persist on a region, line, object, or document with author, timestamp, replies, resolution, and moderation state.
• Use mentions when the user needs to call attention to a person or group inside authored content.
• Use notification center when collaboration events need retained inbox triage; do not notify on ordinary cursor motion.
• Use activity log when a durable event must be recorded; do not treat raw cursor paths as history unless the product explicitly records a session.
• Use sync state and offline state for transport freshness, reconnecting, failed awareness updates, and stale cursor fallbacks.
• Use tooltip only for static help; live cursor labels and cursor chat need identity, motion, recency, and visibility behavior.

Required States

• Local pointer visible, local pointer hidden, remote pointer visible, remote pointer hidden, and reduced-cursor mode.
• Remote text caret, remote selection range, selected object, hover target, viewport-follow, and presentation pointer states.
• Cursor label, avatar, color, name, role, anonymous user, external guest, and duplicate-name states.
• Fresh, delayed, stale, disconnected, reconnecting, permission-hidden, and out-of-viewport cursor states.
• Cursor chat open, typing, sent, expired, dismissed, pinned temporarily, and converted-to-comment states where supported.
• Many collaborators, overlapping cursors, mobile touch pointer, high zoom, low zoom, transformed canvas, and scrolled document states.
• Follow collaborator, stop following, jump to cursor, reveal location, and do-not-follow-presenter states.
• Screen-reader summary, keyboard focus equivalent, privacy-hidden section, and reduced-motion states.

Interaction Contract

• Sending cursor data updates ephemeral awareness state with coordinate, target, viewport, selection, identity, color, timestamp, and visibility preference, not the saved document content.
• Remote cursors are anchored to the same transformed coordinate space as the shared content and remain accurate across scroll, zoom, pan, resize, and object transforms.
• Cursor overlays avoid blocking primary controls; users can hide their own pointer, reduce other pointers, or follow one collaborator without losing editing focus.
• Stale cursors fade, label themselves stale, or disappear according to a clear timeout instead of freezing as if live.
• Permission and privacy rules filter cursor location, object names, private regions, anonymous viewer identity, and external collaborator details before broadcasting.
• Cursor chat remains temporary unless the user deliberately converts it to a comment, task, or other durable artifact.
• Assistive technologies receive concise collaborator-location summaries and change announcements without a noisy stream of every pointer movement.

Implementation Checklist

• Define awareness payloads for pointer coordinates, text caret, selection range, user identity, color, timestamp, viewport, target object, visibility preference, and privacy scope.
• Map cursor coordinates through scroll, zoom, pan, transforms, responsive layouts, and canvas scale before rendering remote overlays.
• Design cursor labels, colors, avatars, stale states, hidden states, follow mode, cursor chat, collision behavior, and reduced-cursor controls.
• Throttle and debounce pointer updates so motion feels live without flooding the network, history, notifications, or assistive announcements.
• Respect permissions for private objects, external guests, anonymous viewers, hidden pointers, view-only mode, and restricted canvas regions.
• Test many collaborators, high zoom, mobile touch, keyboard-only editing, screen reader summaries, reconnects, stale state, out-of-viewport cursors, and cursor-chat expiry.

Common Generated-UI Mistakes

• Using live cursors as durable comments, decision records, or audit history.
• Leaving stale cursor arrows frozen after users disconnect.
• Rendering cursor labels that cover the object users are trying to edit.
• Relying only on color to identify collaborators.
• Broadcasting cursor position in private or permission-limited regions.
• Triggering notifications or feed items for ordinary pointer motion.
• Showing every collaborator cursor in dense sessions with no reduce, hide, or follow controls.
• Failing to transform cursor position correctly when the canvas is zoomed, panned, or scrolled.

Critique Questions

• What shared coordinate system anchors each remote cursor?
• Can users identify each cursor without relying only on color?
• What happens when cursor data is delayed, stale, disconnected, or out of viewport?
• Can users hide their own cursor or reduce other cursor overlays?
• Are private regions, anonymous users, and external guests filtered before cursor location is shared?
• Does cursor chat expire or convert deliberately into a durable comment?
• How do keyboard and screen-reader users learn where collaborators are working?