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Two pointers pinch event. Lambda Signature: (start1: Xy, start2: Xy, end1: Xy, end2: Xy, center: Xy) -> Unit A two pointers pinch event is defined as two pointers down, followed by moving one or both pointers toward or away from each other. "start1" param represents start of the previous position for first pointer "start2" param represents start of the previous position for second pointer "end1" param represents end of the current position for first pointer "end2" param represents end of the current position for second pointer "center" param represents the rotation center