Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you have been placed in read-only mode.
Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. NoScript).
F
to answer my own post, the dev of libretro-cap32 answered me on github. It's a simple matter of switching the virtual keyboard to gamepad emulation by using the SELECT key. Then you can use the virtual keyboard with the mouse. YEAH !