WinForms positioned every control in the panel absolutely, mixing
left-anchored and right-anchored ones. At the design width it looked
fine; narrower than that, Clear Finished slid left over the "At once"
spinner - and the DL Limit label had always slid onto Cancel All the
same way, long before this branch. The two rows also never lined up
with each other, because the labels and the spinners each started at
different offsets.
Cancel All and Clear Finished now dock to the panel edges and the
settings sit in a two-row table between them: labels right-aligned in a
fixed column, controls left-aligned in the next, so "At once" and
"DL Limit" line up and stay lined up. Nothing can overlap, because
nothing is placed by hand any more.
Avalonia's row gained a fourth column for the same setting, which left
less room before the star column collapses and Clear Finished clips.
The spinner asked for 90px to show a number between 1 and 10; 72 is
enough and gives most of that width back.
The 'At once' spinner sat at x136-181 on the second row, but the
'DL Limit:' label starts at x148. Moves the label and spinner up to the
first row beside the Auto-scroll checkbox, where there is clear space
between Cancel All and Clear Finished.
Replaces the MultiThreadEnabled checkbox and the ProcessorCount default
with a single MaxConcurrentDownloads value where 1 means serial - the
behaviour Libation had before parallel downloads existed.
The old pairing could not express 'off' at all: the bool was hardcoded
true in the view model constructor and the int setter clamped to a
minimum of 2, so there was no way back to one-at-a-time downloads.
Collapsing both into one value makes that state unreachable rather than
merely fixed, and removes the risk of the two settings disagreeing.
Bounds live in Configuration as named constants: minimum 1, default 3,
maximum 10. Audible throttles license requests, so the default is
deliberately conservative and the cap keeps users from choosing a number
that produces license denials instead of speed.
WinForms swaps the 'Parallel downloads' checkbox for an 'At once:'
spinner that reads its bounds from those constants.
Allamagoosa