text-properties-at

text-properties-at is a built-in function in `C source code'.

(text-properties-at POSITION &optional OBJECT)

Return the list of properties of the character at POSITION in OBJECT.
If the optional second argument OBJECT is a buffer (or nil, which means
the current buffer), POSITION is a buffer position (integer or marker).
If OBJECT is a string, POSITION is a 0-based index into it.
If POSITION is at the end of OBJECT, the value is nil.