Document the porting process for existing LibRetro / RetroArch cores

[csolisr]

Hydra seems to have a similar architecture to projects such as RetroArch, where emulation cores hook to a unified management and rendering backend. What differences, if any, exist between the Hydra specification and the LibRetro specification? And what changes would be required to port a LibRetro core to Hydra, if possible?

[OFFTKP]

Sorry for keeping you waiting, I just saw this!

The Hydra API aims to provide as many features as possible to emulator developers for creating cores. It is still a work in progress and constantly evolving until release (interfaces may change, thus creating cores at this early stage may require changes in the future). Indeed there's similarities between LibRetro and Hydra, and many functions match one to one, so porting should not be too difficult for a lot of cores. Hydra uses an object oriented approach to designing cores, splitting features into small interfaces that cores can inherit from. For example, there's separate interfaces for rendering, input, cheats, etc. Thanks to this approach, cores don't need to define any unneeded API functions, making Hydra cores easy to write and later extend.

Here's an example of an actively maintained Hydra core for Panda3DS: https://github.com/wheremyfoodat/Panda3DS/blob/master/src/hydra_core.cpp

I will leave this issue open, as a porting process would be good to have in the future, but it will have to be after the API gets to a more stable point.