A new version of GeeXLab is available for Windows (32/64-bit), Linux (64-bit), Mac OS X and Raspberry Pi.
Since GeeXLab version 0.9+, a Direct3D 12 renderer plugin is available in the Windows versions (32 and 64-bit).
This article describes what is
GLSL Hacker GeeXLab and how it works.
Update (2015.12.02): This article is also valid if you replace GLSL Hacker by GeeXLab!
GLSL Hacker does not come with a bloated graphical user interface. Instead, GLSL Hacker uses simple files (*.xml, *.lua, *.py, etc) to store a demo. All you need to create demos with GLSL Hacker is a simple text editor to edit these files.
Today, a small code sample (in Lua) that shows how to use the mouse to put where you want on the screen a letter with random parameters (position, scaling, orientation and color).