This is a platform engine widget I have made up from Nifflas' Sub-Pixel movement example with collision detection.
It's not an advanced platform engine. I basically wanted a decent platform engine that uses floating point movement. I really liked Nifflas' sub-pixel example for floating point movement, so I turned it into a platform engine. There are no other object detectors. It's only one object that does everything.
The only thing I had trouble with was adding the ability to walk up & down slopes. I know Nifflas' has an advanced platform engine that as slopes, but it's not the kind of slopes I wanted. His platform engine makes you fall down deep slopes. I kind of wanted to just walk up and down slopes only. But I guess this will do for now.