P.S. And "untextured" coluld be a single texel stretched wide -- I adapted this strategy for my GUI to avoid unnecessary state switches.

P.P.S. Annoyingly "GL_QUADS" is deprecated and GLES doesn't have it. I went total :rageface: when I tried drawing a textured trapezoid and found that there is no good way except tesselating the tar out of it. What a bummer!
I had to recreate GL_LINE_STRIP on my own because it does not exist either. There are only triangles. Indexed ones.
On the plus side I can now use Google's "GL over Direct3d" wrapper -- ain't that neat?