My pure DotNET library runs as a plugin inside an unmanaged desktop application. I've been getting a steady (though low) stream of crash reports that seem to indicate a problem with GDI handles (fonts in error messages etc. revert to the system font, display of all sorts of controls break down, massive crash shortly after).
My Forms have few controls, but I do a lot of GDI+ drawing in User controls. What's a good way to tell how many handles I'm using, or even leaking?
Thanks, David
I've had to deal with the same kind of problem in the past. In order to inspect how many GDI objects your application is allocating you can use a free tool called GDIUsage.
In my case the application was crashing because it was allocating more than 10.000 GDI objects, which is a hard limit in Windows XP. It might be worth looking into it.
I've blogged about this problem here:
http://megakemp.com/2009/02/25/gdi-memory-leak-in-windows-forms/