> I've got a transparent picture control over a chart. The picture is
> used to place a horizontal line across the chart using a mouse click.
>
> It all works fine until the chart is filled and it has to start
> scrolling. Then it really slows down.
>
> If I move the picture so that it isn't overlapping the chart then the
> chart runs at a good speed again.
>
Charts, like most other controls have more work to do when overlapped.
An overlapped chart can redraw just the small area where the new data is
drawn until it fills up and starts scrolling. At that point, the chart
must redraw the entire chart. One thing you can do is change the update
mode from strip chart to either scope chart or sweep chart. You can
also make the overlay be optional, so that
it doesn't pay the overlap
price except when it needs to.
Greg McKaskle
