I just got the "bright" idea to try this with the RiftDK set to a higher resolution (1920x1200) so the RiftDK controller could downsize my windows allowing me to see more of my desktop farther away.
Nope, broken! The program assumes the RiftDK is running at 1280x800 resolution. But the code is so simple that it should be a simple change to let it work at other RiftDK video resolutions. I may fix it myself, when I get some free time...
My experience is that the RiftDK controller does a poor job of downsampling anyway, making the text almost unreadable. It is much better to downsample the screen in software (such as in this app). I have old WINAPI code in my personal code collection that dynamically resizes a DIBSSECTION, which I will need to find and add into here. I also have some subpixel wobulation resolution enhancement code I wrote and tested in my Rift. It lets me clearly read tiny text only two pixels wide! But (and a big but) it is very dizzy-making in the Rift (but looks GREAT on a large LCD panel). Still, it may be worth making it a user-selectable option, so I may add it into this too. And perhaps cylinder warping, so you are on an elevator in a cylinder covered in video screens, extending from heaven to hell (or vice versa). It would make an awesome photo and video gallery, with side-to-side text not warped, but text at the vertical extremes would not be readable in small fonts...
We could add a VNC client to this program so it can show remote framebuffers on other remote computers. Or we could provide an SDL library so that SDL-based programs can render directly to virtual windows in the Rift VR space...
Imagination is the only real boundary to what we can do, if we can figure out how to overcome or avoid physical limitations of the hardware.
Which reminds me, Doom and Quake will probably work for this without any messing around! Just play them on your main desktop, and view the cropped copy in your RiftDK with head tracking to look around the spherical screen onto which your game is being projected.
EDIT: Okay, I resized my RiftDK display to 1280x800, and positioned it above my main 2560x1440 display. Now the main display starts a little below the horizon, and extends beyond my feet below a little bit behind me. The head tracking messes up trying to look directly at the screen bottom though (RiftDK a little upside-down).