Actually, reading the monitor information is the easy part. The problem stems from the fact that there is no built-in API to handle per-monitor wallpapers. That part has to be handled manually via GDI+ or some other image manipulation library. In other words, the images you want to use have be stitched/cut/cropped into one image that is actually stretched across your two monitors. That's the not-so-easy part. =] Make sense?
-skwire
Sure, makes perfect sense. I see it's not as straightforward as I'd previously thought.
Displayfusion is a useful tool, but interacting with it leaves a lot to be desired; the simplicity of function I've come to relish in DonationCoder-style apps is lacking. I'd venture that a one-click and drag'n'drop style app would fill a gap in the desktop wallpaper management landscape.
Would allowing multiple copies of our theoretical utility to run, one per monitor desktop, make things any easier? (I doubt it but it's an angle I thought needed to be at least mentioned).