set-clickback in text%

Installs a clickback for a given region. If a clickback is already installed for an overlapping region, this clickback takes precedence.

See also Clickbacks.

• (send a-text set-clickback start end f hilite-delta call-on-down?) -> void
     start : exact non-negative integer
     end : exact non-negative integer
     f : procedure of three arguments: a text% object, a starting position exact non-negative integer, and an ending position exact non-negative integer
     hilite-delta = #f : style-delta% object or #f
   call-on-down? = #f : boolean

  The callback procedure f is called when the user selects the clickback. The arguments to f are this editor and the starting and ending range of the clickback.

  The hilite-delta style delta is applied to the clickback text when the user has clicked and is still holding the mouse over the clickback. If hilite-delta is #f, then the clickback region's style is not changed when it is being selected.

  If call-on-down? is not #f, the clickback is called immediately when the user clicks the mouse button down, instead of after a mouse-up event. The hilite-delta argument is not used in this case.