An installed app and a browser tab are one origin, one catalogue and one roll.
Without a word between them the second window opens, finds nothing in flight,
and reads the same frames again — two readers of one folder, two RAW decoders at
256MB apiece, for a progress the first window already has.
The window holding the reading now announces it on every frame and on a
heartbeat, and answers a window that has just opened and asks. A window that
does not hold the reading takes it as its own: the same progress line, the
folder marked as being read, the same STOP — which it relays rather than
redirects — and the same jump. What it does not do is read the disk.
A reading that is through leaves the catalogue behind, and a window watching it
has nothing left to be told, so the screen reads the catalogue back once more
when the session goes away: the frames that arrived with the last flush would
otherwise never be drawn in the window that was only watching.
Measured over one origin (two pages, 24 RAW frames): the second window read 25
frames before and 1 after (the open frame), the peak over an idle browser fell
from 1412MB to 1155MB against 944MB for a single reader.
3dtours
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