Okay, so, I had a problem where whenever I tried to resize or move my window, rendering would halt. Which was weird, because my Render() function isn't in WndProc at all, it's in my main loop. I partially solved this by having WM_SIZE and WM_MOVE both call the Render() function, but the animation still stops whenever I click on the title bar or on the border of the window. I've been hunting for what message windows sends when it does this, as WM_ENTERSIZEMOVE is the closest I got, but that only gets sent once, not every frame like WM_MOVE or WM_SIZE. I tried making WM_ENTERSIZEMOVE turn on a bool that tells WndProc whether or not to render, but that just didn't work at all. The main reason that this is an issue is because while the animation stops, the music (playing via OpenAL) does not, which could easily cause sync issues down the line.
I could make it so that the programs is suspended whenever focus of the window is lost, which I presume would be any case that would get in the way of rendering, but I'd much rather just make it keep rendering no matter what the user is doing (unless they're in another window - I already check for that via WM_ACTIVATE).
(I apologize, this probably isn't an OpenGL-specific question, but it's been bugging me nonetheless).