lib/Ext/util/LineSegment.js
function(lineSegment) {
        var point1 = this.point1,
            point2 = this.point2,
            point3 = lineSegment.point1,
            point4 = lineSegment.point2,
            x1 = point1.x,
            x2 = point2.x,
            x3 = point3.x,
            x4 = point4.x,
            y1 = point1.y,
            y2 = point2.y,
            y3 = point3.y,
            y4 = point4.y,
            d = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4),
            xi, yi;

        if (d == 0) {
            return null;
        }

        xi = ((x3 - x4) * (x1 * y2 - y1 * x2) - (x1 - x2) * (x3 * y4 - y3 * x4)) / d;
        yi = ((y3 - y4) * (x1 * y2 - y1 * x2) - (y1 - y2) * (x3 * y4 - y3 * x4)) / d;

        if (xi < Math.min(x1, x2) || xi > Math.max(x1, x2)
            || xi < Math.min(x3, x4) || xi > Math.max(x3, x4)
            || yi < Math.min(y1, y2) || yi > Math.max(y1, y2)
            || yi < Math.min(y3, y4) || yi > Math.max(y3, y4)) {
            return null;
        }

        return new Ext.util.Point(xi, yi);
    }
function(lineSegment) {
        var point1 = this.point1,
            point2 = this.point2,
            point3 = lineSegment.point1,
            point4 = lineSegment.point2,
            x1 = point1.x,
            x2 = point2.x,
            x3 = point3.x,
            x4 = point4.x,
            y1 = point1.y,
            y2 = point2.y,
            y3 = point3.y,
            y4 = point4.y,
            d = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4),
            xi, yi;

        if (d == 0) {
            return null;
        }

        xi = ((x3 - x4) * (x1 * y2 - y1 * x2) - (x1 - x2) * (x3 * y4 - y3 * x4)) / d;
        yi = ((y3 - y4) * (x1 * y2 - y1 * x2) - (y1 - y2) * (x3 * y4 - y3 * x4)) / d;

        if (xi < Math.min(x1, x2) || xi > Math.max(x1, x2)
            || xi < Math.min(x3, x4) || xi > Math.max(x3, x4)
            || yi < Math.min(y1, y2) || yi > Math.max(y1, y2)
            || yi < Math.min(y3, y4) || yi > Math.max(y3, y4)) {
            return null;
        }

        return new Ext.util.Point(xi, yi);
    }
Returns the point where two lines intersect.
@param {Ext.util.LineSegment} lineSegment The line to intersect with.
@return {Ext.util.Point}