15. A pointer-based computer system as recited in claim 14 wherein said means for determining whether said theoretical line is a division gesture includes one or more of the following: means for determining whether there is a sample point further from said theoretical line than a predetermined maximum distance value; means for determining whether the absolute value of a sum of the signed distances of said plurality of sample points from said theoretical line is greater than a predetermined maximum sum value; means for determining whether the absolute value of a slope of said theoretical line differs from a predetermined header bar slope by more than a predetermined maximum slope value; and means for determining whether either end of said theoretical line is separated from an edge of said screen by more than a predetermined maximum margin value wherein when one of the determining means fails, said theoretical line is not a division gesture.
14. A pointer-based computer system as recited in claim 13 wherein said means for detecting a theoretical line comprises: means for collecting a plurality of sample points corresponding to a movement of said pointer across said display; and means for forming said theoretical line from at least two of said plurality of sample points.