The code point index of the first code point in the cluster that the point is closest to.
public int ClosestCodePointIndex;
If the point is over a cluster, the returned code point index will vary depending whether the point is in the left or right half of the cluster and the text direction of that cluster.
This value represents the code point index that the caret should be moved to if the user clicked the mouse at this position. To determine the co-ordinates and shape of the caret, see Caret Information.