XMandelbrot
A Mandelbrot Set Generator for the X Window System (X11)
This is truly ancient software. XMandelbrot is a
C++ project that displays a mandelbrot set in a window,
accomplishing this with the help of the api for the X11
/ X Window System common to linux / unix platforms
alone.
No additional framework, gui development form the ground
up.
Even at the time I wrote this, doing gui development solely using the X11 api was pretty much obsolete (I think). Nevertheless, it provided valuable insight into gui development and doing things from the ground up can be pretty nice sometimes as well.
If you want to check it out, you can get the tarball from here, run make once you've unpacked it and have a look.