The distance scrolled by the scroll-line gesture.
The distance scrolled by clicking inside the scroll bar.
A function called after a scroll gesture, or
implements panes which display a scroll bar and call a callback when the user scrolls. It is not however the most usual way to add scroll bars - see the note below about simple-pane.
line-size is the logical size of a line, and is the distance moved when the user enters a scroll-line gesture, that is clicking on one of the arrow buttons at either end of the scroll bar or using a suitable arrow key. The default value of line-size is 1.
, meaning there is no callback. This is the default value. Otherwise, is a function of four arguments, the interface containing the scroll-bar, the scroll-bar itself, the mode of scrolling and the amount of scrolling. It has this signature:
Note: the location of the slug can be found by the range-pane accessor
Note: Rather than using
, it is more usual to add scroll bars to a pane by the simple-pane initargs