Blendish is a small collection of drawing functions for NanoVG in a single C header file, designed to replicate the look of the Blender 2.5+ User Interface. You can use these functions to theme your UI library. Some metric constants for faithful reproduction are also included.
The repository also hosts OUI (short for "Open UI", spoken like the french "oui" for "yes"), a platform agnostic single-header C library for layouting GUI elements and handling related user input. Together with a set of widget drawing and logic routines it can be used to build complex user interfaces.
Here's a screenshot of Blendish styling a set of layouted OUI items (also contained in example.cpp).
Here's a shot of all available Blendish theming functions: