This release is mainly aimed at developers integrating projectM into their applications. The main focus of this major release was to provide a new, stable API based on pure C functions, which will make it easier to create bindings for other languages as well as using it as a shared library. We also fixed many crashes and improved the overall visual quality and compatibility of presets to some degree.
The API will remain stable and forward-compatible until the next major release. Any changes made will only include new functions, so the ABI will always stay forward-compatible. This means an application built and linked against a specific 4.x version will build and run with any libprojectM with a major version of 4 and the same or higher minor version. If an application uses libprojectM as a shared library, no relinking is required at all - simply swap the library file with the new one and it should work.
https://github.com/projectM-visualizer/projectm/releases