Pop up a menu dialog to alter the settings specific to the applicable engine.
(The second engine is only accessible once it has been used in Two-Machines mode.)
For each parameter the engine allows to be set,
a control element will appear in this dialog that can be used to alter the value.
Depending on the type of parameter (text string, number, multiple choice,
on/off switch, instantaneous signal) the appropriate control will appear,
with a description next to it.
XBoard has no idea what these values mean; it just passes them on to the engine.
How this dialog looks is completely determined by the engine,
and XBoard just passes it on to the user.
Many engines do not have any parameters that can be set by the user,
and in that case the dialog will be empty (except for the OK and cancel buttons).
UCI engines usually have many parameters. (But these are only visible with
a sufficiently modern version of the Polyglot adapter needed to run UCI engines,
e.g. Polyglot 1.4.55b.) For native XBoard engines this is less common.
Hint
Displays a move hint from the chess engine.
Book
Displays a list of possible moves from the chess engine's opening
book. The exact format depends on what chess engine you are using.
With GNU Chess 4, the first column gives moves, the second column
gives one possible response for each move, and the third column shows
the number of lines in the book that include the move from the first
column. If you select this option and nothing happens, the chess
engine is out of its book or does not support this feature.
Move Now
Forces the chess engine to move immediately. Chess engine mode only.
The Ctrl-M key is a keyboard equivalent.
Retract Move
Retracts your last move. In chess engine mode, you can do this only
after the chess engine has replied to your move; if the chess engine is still
thinking, use ‘Move Now’ first. In ICS mode, ‘Retract Move’
issues the command ‘takeback 1’ or ‘takeback 2’
depending on whether it is your opponent's move or yours.
The Ctrl-X key is a keyboard equivalent.