6.99.36 — the stale reopen, and an eraser that takes the first pass

Two of the three things reported against v6.99.35.

Tapping the ink opened the previous drawing

The attachment endpoint answers private, max-age=3600 and sends no ETag, so
the browser serves a second read of the same path out of its cache for an hour
without asking the server. An ink file changes under a fixed name every time it
is saved, so that cached answer is the drawing as it stood before the last
edit — and the canvas opened on it. v6.99.34 fixed this for the picture shown in
the note; the file the canvas itself reads was still being cached.

Reproduced in a desktop browser before fixing: the second reopen loaded exactly
the pixel count the first one had.

The eraser needed several passes

It measured each sample the browser reported, not the path between them. The pen
is reported tens of pixels at a time, so a thin line crossed between two reports
was a line you watched the eraser go through without taking.

It now tests the eraser's path against the stroke, segment against segment, and
tests crossing before measuring any distance — two segments that cross are
nought apart, and no measurement from an end point will say so. The path is
carried across reports too, so the gap between one and the next is covered;
never across a lift, since the line back to where the eraser was last put down
would take whatever it crossed.

The eraser now draws its own outline under the pen, so it can be aimed. An
outline rather than a disc, because what matters is seeing which marks are
inside it.

Still open

The canvas opening at the size of the previous save. Not reproduced: in a
desktop browser the dialog is the full viewport both on a first open and on a
reopen over a small picture. Needs a look at the device.