A roll is dated folders inside dated folders, and the reader who wants April
re-read is not a reader who asked for the four years around it. Right-clicking a
subfolder row carried the roll's own menu, and RESCAN on it read the whole tree
from the top — every folder of every layer opened again, every frame in them
asked for its size and its time, to reach the one folder the pointer was on. On
a library of a hundred thousand that is a walk of minutes for a folder of
twenty.
The scan now takes the folder it was pointed at, spelled as the walk spells a
path: '' for the picked folder, `2026/04/` for a subfolder. The walk is handed
that path as its queue and reads down from there, so the tree is entered three
levels in rather than at its root, and the menu row passes the path of the row
under the pointer. A right click on the head of the tree still reads the whole
roll, which is what a right click on the picked folder has always meant.
What a reading kept to one folder must not do is speak for the roll. What it
names in the column is a branch of the tree, so the column keeps what it has and
the rows outside the folder being re-read stand where they are. What it counts
is a branch too, and its numbers drawn over the rows would count a roll down to
one folder of itself, so the column falls back on the catalogue until the
reading is through — the frame the reader is waiting for is the frame that was
re-read, and it is in the column the moment it lands.
Nor does it write a position down. `walk/ROLL.json` belongs to the reading that
walks the whole roll: a fraction of the tree written into it hands the next
visit a roll with the rest of itself missing from the walk, and it clears a file
another reading may be in the middle of. One folder is short enough to read
again, and the frames it does not re-read are skipped on their size and their
time anyway. A jump is refused for the same reason — the reading answers to the
folder it was kept to, and a click elsewhere is a different reading's business.
3dtours
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