> without some kind of direct rendering going on, I can't see how this would work on a terminal emulator.

Nah.

You just dump the pixels one by one to the screen using a for loop. You can even do some cpu math with each pixel if you want, and at the end you call XPutImage with the raster (or whatever your toolkit offers). This runs at more than 30fps in fullhd on a 10 year old cpu.

Notice that xterm is blazingly fast and runs entirely on the cpu. Think about it, the plots that this iterm2 demo shows were already done in realtime in the late nineties using the first pentium cpus.

The GPU is not really needed for the basic stuff a terminal emulator does. Of course, if you want to do crazy stuff like scaling by enormous factors, or ultra-fast scroll without skipping tricks, you'll need GPU support.

I see. I'm not nearly qualified enough to talk about that, admittedly. Drawing the pixels isn't the problem, it's updating them fast enough, then?

I guess there is no problem? You only need the gpu to compute fancy 3d graphics in high resolution. For normal terminal stuff and low resolution plots, anything should work.