Rasterizing a view is most of a second, so the paint that answers a pan
drew the nodes on an empty canvas and waited — the map going black on
every keypress and flashing back when the frame landed. Each finished
frame now keeps its braille layer, and the next moved view stands on it:
the two viewports differ by an affine scale-and-shift in Web Mercator,
which collapses to two cell-index tables the canvas pastes by. So the
streets slide with the view — dimmed, and short of the edge you are
panning onto — until their own raster replaces them.
Cell granularity, not dot-exact: the stand-in lands within half a cell
of true and is corrected a moment later, for +0.5 ms on the paint path
instead of eight times the work. Only the ground travels; labels and
markers are redrawn where they really are. The fade is off on the
16-slot console, where dimming a colour is a recolouring, and the whole
ghost is dropped once it says nothing — panned clear off, or more than
two zoom steps away.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Jean-Pierre MartineauandClaude Opus 5
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