Clusters at dense zoom

When fifty events shrink to three pixels each, cluster: true draws one marker over the run, with their count on it. Zoom out in the log recipe to see them form; tap one, or focus it and press Enter, and it opens.

  // Events too close to tell apart become one marker with their count.
  cluster: true,

What joins

Neighbours in one row whose drawn boxes are less than gap pixels apart (4), when each is drawn shorter than itemSize (12). An open interval, a band taller than a row, or anything long enough to read stays itself and ends the run. A run shorter than minCount (2) is drawn as items. Pass { gap, itemSize, minCount } instead of true to tune it.

• Decided in time, from the zoom level alone. A pan never splits a cluster or changes a count; only a zoom does. A cluster never spans rows.
• A cluster is all of its members. It is drawn when any of them would be, and its count is its size, not the part on screen.
• Opening zooms so the cluster's time fills half the view (at least 2×), anchored where the user tapped. Members that are still too many come apart into smaller clusters — the next tap's target. Every opening emits clusterOpened with the cluster; at the zoom limit, where a cluster still holds, its members are the host's to show as a list.
• One stop for the keyboard and the reader: the arrows step over a cluster as one entry, and a cluster is never edited.

hooks.describeCluster names it in your language, hooks.renderCluster draws it. Without cluster, a frame is byte for byte what it was.

That is a gate: about 29 000 seeded frames are read back and compared with the same frame unclustered — every visible item is represented exactly once — and a real browser checks the live DOM after every wheel zoom, drag, tap and key.