--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dwtx/draw2d/geometry/Geometry.d	Sun Aug 03 00:52:14 2008 +0200
@@ -0,0 +1,78 @@
+/*******************************************************************************
+ * Copyright (c) 2005, 2008 IBM Corporation and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ * Port to the D programming language:
+ *     Frank Benoit <benoit@tionex.de>
+ *******************************************************************************/
+module dwtx.draw2d.geometry.Geometry;
+
+import dwt.dwthelper.utils;
+
+/**
+ * A Utilities class for geometry operations.
+ * @author Pratik Shah
+ * @since 3.1
+ */
+public class Geometry
+{
+
+/**
+ * Determines whether the two line segments formed by the given coordinates intersect.  If
+ * one of the two line segments starts or ends on the other line, then they are considered
+ * to be intersecting.
+ *
+ * @param ux x coordinate of starting point of line 1
+ * @param uy y coordinate of starting point of line 1
+ * @param vx x coordinate of ending point of line 1
+ * @param vy y coordinate of endpoing point of line 1
+ * @param sx x coordinate of the starting point of line 2
+ * @param sy y coordinate of the starting point of line 2
+ * @param tx x coordinate of the ending point of line 2
+ * @param ty y coordinate of the ending point of line 2
+ * @return <code>true</code> if the two line segments formed by the given coordinates
+ *         cross
+ * @since 3.1
+ */
+public static bool linesIntersect(int ux, int uy, int vx, int vy,
+        int sx, int sy, int tx, int ty) {
+    /*
+     * Given the segments: u-------v. s-------t. If s->t is inside the triangle u-v-s,
+     * then check whether the line u->u splits the line s->t.
+     */
+    /* Values are casted to long to avoid integer overflows */
+    long usX = cast(long) ux - sx;
+    long usY = cast(long) uy - sy;
+    long vsX = cast(long) vx - sx;
+    long vsY = cast(long) vy - sy;
+    long stX = cast(long) sx - tx;
+    long stY = cast(long) sy - ty;
+    if (productSign(cross(vsX, vsY, stX, stY), cross(stX, stY, usX, usY)) >= 0) {
+        long vuX = cast(long) vx - ux;
+        long vuY = cast(long) vy - uy;
+        long utX = cast(long) ux - tx;
+        long utY = cast(long) uy - ty;
+        return productSign(cross(-usX, -usY, vuX, vuY), cross(vuX, vuY, utX, utY)) <= 0;
+    }
+    return false;
+}
+
+private static int productSign(long x, long y) {
+    if (x is 0 || y is 0) {
+        return 0;
+    } else if (x < 0 ^ y < 0) {
+        return -1;
+    }
+    return 1;
+}
+
+private static long cross(long x1, long y1, long x2, long y2) {
+    return x1 * y2 - x2 * y1;
+}
+
+}