Is there a library that knows what position my mouse is at on my screen. I have a wireless mouse on a Mac and would like something like a .getMouseX, if you know what I mean.
At the very least you are going to need a program running on the PC to tell the Arduino where the mouse is. Have you got such a program.
Some Arduinos, notably the Leonardo, can control the mouse, but cannot determine where it is currently positioned.
Ahh, I do not have such a thing. I am currently making a project on a TFT (not the Arduino one but an Adafruit version) where I have it painting and such and I was hoping it would be possible to control the paintbrush on the screen somehow, but I understand that this idea won't work now that I don't have what you are telling me about.
Is the TFT screen attached to the Arduino or the Mac ?
You can use a PS2 mouse as an input device connected directly to your Arduino.
If you get a USB host shield it might be possible to connect a USB mouse to your Arduino. I'm not sure about that but the information should be out there if it is doable.