As part of this blog I wanted to talk about my failures as well as my successes, so in the spirit of that I'll talk about things which have tripped me up recently and what the solution was, in the hope that someone else with the same problem might be able to learn something.
Full Screen Mode
One of the early things I implemented in the main engine was the ability to go to full screen mode. It's not a big thing, its pretty much in every game. Though you need to properly reset the Direct3D device and free up all your resources and load them in again in order for it to work. Which can be tricky for those unfamiliar with Direct3D to get their head around. I consulted many tutorials and got it working and then ignored it for several months.
I switched the game to full screen mode on the weekend and the screen resized to fit the entire screen but the rendering stopped, and the entire app hung. Obviously I'd broken something in the last few months. To cut a long story short, I'd implemented a new way of handling the Resize events and that was firing when it shouldn't and was stopping the rendering. After I fixed that, it worked again... mostly.
My UI elements, (which admittedly didn't exist when I coded the full screen mode) were not receiving mouse clicks correctly, as though the coordinate systems were offset somehow. I discovered that the actual dimensions of the full screen window weren't correct. Though I was setting it to be 1680x1050 (the max resolution of the laptop I do development on), the window was coming out as 1664x1015 or something. Stretched across the entire screen this would cause misalignment of the mouse cursor vs the controls and exhibit the behaviour I noted.
After much googling, I finally discovered that you need to set the borderstyle of the form to none when going to fullscreen and then restore it when switching back. When I originally implemented full screen mode that little quirk wasn't mentioned in the tutorials I looked at, and because it looked correct, I assumed it was correct, due to the perception that full screen mode should have been a cinch.
I guess the lesson here is never assume that you're done correctly just because it's a simple task, and the output seems correct.