Sets the current selection in the buffer.
Setting the position is disallowed when the buffer is internally locked for reflowing (see also Locks).
See End of Line for a discussion of at-eol?. If scroll? is not #f, then the view is scrolled to show the selection if necessary.
The seltype argument is only used when the X Windows selection mechanism is enabled. The possible values are:
See also wx:media-set-x-selection-mode.