Mouse Input

I would most likely use SDL_GetRelativeMouseState (or SDL_GetMouseState with a little extra code) while performing a check for the particular button in question, and basing my results off of that. For example if I wanted to know how where the mouse moved from, and to where, while a button was being held down.

Both functions return a bit string that determines which buttons are currently pressed, and also take two parameters which will be filled with the respective x and y mouse coordinates. Check the documentation site listed in the last post for a good overview, or just do a quick search for the functions on Google.