WLD is the new (and very simple) Wayland drawing library that's been christened. Michael Forney, an independent developer, was wanting to port ST (a simple terminal emulator for X) and Dmenu (a dynamic menu for X) to Wayland. However, with the current Wayland render back-ends being overkill for such simple/basic programs, he decided to write his own implementation.
ST and Dmenu are classic X11 programs and basically need only the ability to draw colored rectangles and monochrome text, but certainly don't need a full 3D API or even advanced 2D drawing. With needing only primitive draw and text support, WLD was created as a Wayland library to accomplish drawing colored rectangles and monochrome text.
WLD in turn has back-ends for using the Pixman renderer on Wayland or directly the BLT engine for Intel GPUs. The text support is rendered through FreeType. WLD can also work on non-Wayland back-ends due to the common yet portable use of Pixman and FreeType with them being able to create contexts in other environments.
Those wishing to learn more about this simple Wayland drawing library can find the announcement with many more details on the Wayland mailing list.