This is an C-SDL2 example.

It demonstrates how to receive...

filenames & text
via SDL_DropEvent

!!! ATTENTION SHADERTOY API CURRENTLY NOT WORKING
check this link to see if the API is working:
https://www.shadertoy.com/api/v1/shaders/MslGWN?key=fdrtwr

For the last example I use curl and jansson.
see:
https://github.com/Acry/curl_jansson
for more details.
Added working example without API and reflecting latest json changes.

Other useful links:
SDL2 SDL-Discourse More SDL2 example Code
More C Example Code

Screenshots: