gtk - garbage toolkit

GTk is bloated trash due to its dependencies like GLib, cairo and DBus.
Qt4/5 is equally bloated C++ garbage.

OpenVG used to be a saner alternative to cairo, but it's fallen by the wayside and support for it in Gallium has been dropped and might end up getting removed from Mesa in the future.

So if you were to throw away gtk and qt, and starting from first principles, how would you go about building a minimalist themable widget library on top of GL/GLES for Wayland that can be used to build a desktop where applications have a common look-and-feel?

>>7

Tcl/Tk

this is somewhat good

plain Xlib, or maybe XCB

this is the library that you would implement a widget toolkit in terms of, but it seems to be extremely difficult to do this. The information is not available these days.