Scrolling Canvasses in Sunview

[christopher-robin!cjr at cs.utexas.edu]

I have a program which opens a canvas inside a frame, and the canvas has
two scrollbars, so:

    canvas = window_create(frame, CANVAS,
                           ...
                           WIN_HORIZONTAL_SCROLLBAR, scrollbar_create(0),
                           WIN_VERTICAL_SCROLLBAR, scrollbar_create(0),
                           0);

This is the same as in the SunView manuals.  But, this doesn't appear to
detect any button presses over the 'page buttons', so I can only kind of
drag the bar up and down (or left and right).

How can I get the full scrollbar behaviour?  The Sun manuals are not
desperately helpful on this score.

-- Chris Ridd, Computer Science, Birmingham Uni, UK -- RiddCJ at Cs.Bham.Ac.Uk --