...CLIck is written in ANSI C and tested on C and C++ applications on several architectures.
It doesn't depend on any external library and uses only a very small subset of POSIX APIs.
Despite the project name, you won't need your mouse at all!
MTK is a minimalist toolkit for LPC24xx development boards with QVGA displays with touchscreen.
It uses standard linux framebuffer and has double buffered system to prevent flickering.
This project is a GPLed OSS project, which is developed and maintained by Feynman Software. It aims to provide a fast, stable, lightweight, and cross-platform Graphics User Interface support system, which is especially fit for real-time embedded systems.
PW is a small graphics and windowing library. It was designed especially for small embedded systems using 1 bit graphic LCDs. It is very portable, written in ANSI-C and has a small memory footprint.