One interesting thing about the XView toolkit: it built the entire UI out of fonts (bitmap fonts at the time). It supposedly allowed faster rendering because the fonts were loaded and were server side.

I actually used the low layer display layer under XView for some UI projects. Worked great!

While I'm here, the other nice thing about programming in SunView (and later XView) was the use of varargs call patterns to build UI elements. Early X development, as I recall, was significantly more verbose than the Sun equivalent, though probably more type safe. The *View APIs felt a little more like today's high level languages.