I could not resist the temptation of adding a cool new feature:
Right-clicking in the Engine-Output window in-between the words 'fewer'
and 'more' (of the multi-PV header displayed during analysis for engines
that have a MultiPV option), now checks if the engine has an option with
'multi', 'PV' and 'margin' in the name. And if it has, moving the mouse
horizontally then tunes the value of that option (with feedback in the
main-window message field). Clicking on 'fewer' or 'more' still
decrements/increment the value of the MultiPV option (if the engine has
one), as before.
This makes it easier to use Fairy-Max' "Multi-PV margin" option.
The problem with highlighting of PVs in the Engine-Output window during
PV walk is now also fixed. I hope that makes the text-disappearance
problem there also go away.
That leaves Tamerlane Chess as "loose end". Perhaps the easiest way to
meet the demands here (which also would be generally useful) is to
implement a new engine->GUI command 'choice', which can be used to
specify a list of pieces that the 'lifted' piece could promote to, as
part of the 'highlight' feature. And make sure that moves to a square
highlighted by the engine are always accepted, even when XBoard thinks
they are illegal, and legality testing is on. I will try to fix this today.
