Oh man, the first graphics code I ever wrote used Tektronix vector commands for drawing. It used ASCII escape sequences to specify diagonal lines on the screen, but, as I recall you could also tell it that instead of drawing a diagonal line, you could have it draw a rectangle with what would have been the endpoints of the diagonal line being opposite corners of the rectangle. These codes were supported by some VT-series graphics terminals as well as at least one dial-up terminal program on the PC back in the 80s so that’s what I targeted on my code (which was a DVI previewer for TeX running under VM/CMS).
The original Tektronix terminals (I only ever saw one once) did all screen drawing with these vector commands (think the look of the classic Asteroids game which I think may have used a similar hardware interface to the CRT display), which naturally was not especially fast for ordinary text which is why hybrids like the abovementioned VT-series terminal (I think it was the 240/340/440 that had this) ended up supplanting the Tektronix displays.