A phone had started allowing zoom-out, which is how a document wider than the
viewport announces itself. The suspect was the "Ate" modal, but the dialogs are
not it: all seven open with showModal(), so their containing block is the
viewport and width: calc(100% - 32px) cannot exceed it.
It was the month grid, added three commits ago:
left: 50%; transform: translateX(-50%); width: 268px;
max-width bounded the panel's width and nothing bounded its position. Centred
on the date button — which sits near the right edge of the bar — a 268px panel
hangs off the side of a phone, and being absolutely positioned it drags the
document's scrollable width out with it.
Anchoring to the button cannot be made safe: pin it right and it overflows the
left on a narrow screen, pin it left and it overflows the right. So it is a
child of the day bar now, pinned to that bar's inner edge and capped at the
bar's own width. The bar spans the content width exactly, so the panel is on
screen at every size by construction.
A long unbroken word was a second way in, and a pre-existing one. A history
row's note is a flex item with neither min-width: 0 nor a break rule, so a URL
or something copied off a food bag sets its content-based minimum and widens
the row. The Notes log directly below already guarded against precisely this,
so the history row had simply been missed; exercise names and their
instructions had the same gap.
The checks gained the general form of both, since this class of bug is
invisible until a phone starts zooming out: every element that renders text the
user typed must be able to break a long word, the grid must stay edge-anchored
inside the bar, and no fixed width may exceed the content box of a 320px phone.
Each was confirmed to fail with its fix reverted.
Alexander Heldt
14cad44d9b