CincomSmalltalkWiki: scrolling

The VisualWorks 3.0 ScrollWrapper uses the #preferredBounds of its #component to compute the extent of the underlying data. The scrolling does not work correctly if these preferredBounds have an origin ~= 0@0.

You might wonder why this is a problem. On constant data there is no problem at all. If the data grows towards the lower right side, there is no problem, either. But imagine a graph editor that allows you to drag & drop nodes to every position you like. This editor needs an extended working area. This working area is the area where you may drop nodes. After each move the editor recomputes the working area. It is not important weather the working area and the preferred bounds are the same. But you will have to admit that the preferred bound might change during the editing process.

I did not notice any visible effects my patch might have to the functionality of the VisualWorks base system. In the complex graphics environment I work on, the scrolling behaviour is much better if the patch is included.

patch

example

Sascha Dördelmann

Note Jan. 2003: Checked VisualWorks 7.1 against this patch and found it has been integrated. Thanks!