Jay
[hidden email] wrote August 26, 2014 7:29 AM:
> We have an application written in Vw5i and its been used by several
> customers for more than 20 years. However, recently few customers
> are reporting an issue with rubber band selection. Rubber Banding
> of a piece of equipment and then the selection box going away
> or behind the screen. This is the first time we are hearing this
> issue since the application is launched( since 15 years).
> And none of us were able to replicate the same issue in any of our
> development environments.
Rubber banding worked by making a copy of the whole Windows desktop as a
bitmap, then making a fake window with no border covering the whole desktop
and containing that bitmap, then drawing on top of that window. This is known
to fail if the size of the bitmap is greater than the graphics system can
return. VW likes to get bitmaps that are allocated directly on the graphics
card, so with a graphics card with a small amount of memory available
(unfragmented and not allocated for something else), and a large screen /
bitdepth / multiple monitors, it's quite easy to get a failure getting the
bitmap. Windows has also increased restrictions on what applications are
allowed to do with graphics, so that might have an effect too.
Search the web for "Limitations on Windows of displayShape: methods", e.g.
p1-5 in
http://www.cincomsmalltalk.com/main/documentation/VisualWorks/ReleaseNotes7.8.pdf
All the best,
Steve
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