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While I was doing some setup on a target machine, I left my demo application open in the background while I installed some tools.

It seems that when UAC triggers, I get the following error:

Runtime Error 501 - Image number illegal at line 394

I even tried adding this immediately before the line in question:
if screen invalid() then makeimage()

I've managed to repeat the issue multiple times. A minimal test case is attached; simply execute that, leave the window running, and trigger UAC. I'm using the indigo beta installer (since I was setting up my DBP toolchain on the machine).


Yes, normally I would have UAC disabled, but this is a new machine, and UAC is likely to be enabled on end user machines anyway, so it'd be helpful to know how to prevent this problem.

Using UAC triggers a resolution change, which in turn forces DirectX to flush the graphics buffer of all graphical elements loaded in. This isn't a DBP issue, its an unfortunate side effect of the way Windows/DX have been made.

In order to prevent this from happening, you need to check each and every time a graphical element is used that it exists still, and if not, call your media loading function again.

Hope that helps.