Auto-zoom from click telemetry — ED.17

In a busy cutting room the assistant editor kept a continuity log — every take, every notable beat, marked against the footage so the editor knew where the action was without re-screening everything. A screen recording keeps its own continuity log for free: every place the user clicked is a place their attention went. ED.17 reads that log and marks up the timeline with proposed push-ins — the assistant's annotations, which the editor (you) then keeps, nudges, or throws away.

flowchart LR
  LOG["click log\n(frame + x,y per click)"] --> CL["cluster by time gap (~1s)"]
  CL --> WIN["per cluster: window =\n[first − lead, last + hold],\ntarget = centroid"]
  WIN --> ZS["ZoomSegment { Manual(x,y), max_zoom }"]
  ZS --> ENG["ED.16 engine compiles\neach to a push-in"]

auto_zoom_segments is pure arithmetic over a ClickEvent list: clicks within ~1 s cluster together; each cluster becomes a zoom that opens ~0.3 s before the first click, holds AutoZoomConfig::hold_time_ms past the last, and targets the cluster's centroid at max_zoom. Sub-half- second blips are dropped and adjacent windows are clamped so they never overlap. The output is an ordinary list of ZoomSegments — the zoom engine compiles them exactly like hand-authored ones, and the zoom lane renders them for editing.

Capturing the telemetry

The generator consumes a click log + a cursor track; the capture that produces them lives in app::cursor_capture (macOS first):

• Cursor position — a CursorPoller samples the global pointer at ~60 Hz via CGEventCreate(NULL) + CGEventGetLocation, which read the current position with no Input-Monitoring permission and no event tap. samples_to_track resamples the timestamped samples onto the project frame grid; normalize_cursor_to_frame maps display points into the [0, 1] CursorSample convention. Both are pure + unit-tested; the poller thread is runtime-only.