DrawWindow error?

[Doug Gordon]

I have a form that has two sets of controls on that are hidden or shown 
(FrmShowObject, FrmHideObject) depending on the state of a pair of grouped 
pushbuttons. When one of these in particular is pressed, my handler switches 
the objects' states, then updates the now unhidden table and scrollbar. The 
form displays correctly at this point. If the next thing that the user does 
is to press the page-dn button, my handler scrolls the table contents and 
updates the scroll bar. But the first call that I make to a function that 
will affect a control, such as SclSetScrollBar, the POSE emulator with M505 
debug ROM reports an error reading from 0x80000020, which it says can be 
caused by calling a "Window Mgr function without first establishing a valid 
Draw Window".

What is really strange is that if, instead of using the key, I tap in the 
scrollbar area to page it down (which goes through the same code in my app), 
it works OK. And once it has scrolled, the page-up/down keys now work OK 
with no errors. It is only the first time after switching to that form state 
that the error occurs, and only in response to a key press as opposed to a 
tap on a control.

Any ideas what to look for? This is a very stable application that I am just 
trying to add new functionality to. Oh, by the way, the app appears to work 
OK on an actual M505 device. But I really don't like it that the emulator is 
seeing this problem.

 Doug Gordon 


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