Simplify Rectangle.intersects (#302)

Simplify and optimize the intersects checking method of Rectangle. Also
align the behavior of Rectangle.intersect for empty intersections.

Signed-off-by: Martin Jobst <[email protected]>

Author: mx990

org.eclipse.draw2d.tests/src/org/eclipse/draw2d/test/RectangleTest.java

@@ -260,6 +260,14 @@ public void testIntersects() throws Exception {
 		assertFalse(rectangle1.intersects(new Rectangle(-100, -100, 10, 10)));
 		//
 		assertFalse(rectangle1.intersects(new Rectangle(0, 0, 5, 10)));
+		//
+		assertFalse(rectangle1.intersects(new Rectangle(15, 20, 0, 10)));
+		assertFalse(rectangle1.intersects(new Rectangle(15, 20, 10, 0)));
+		//
+		Rectangle rectangle3 = new Rectangle(0, 30, 0, 40);
+		assertFalse(rectangle3.intersects(rectangle3));
+		//
+		assertFalse(rectangle3.intersects(new Rectangle(0, 30, 100, 10)));
 	}
 
 	@SuppressWarnings("static-method")

org.eclipse.draw2d/src/org/eclipse/draw2d/geometry/Rectangle.java

@@ -725,7 +725,7 @@ public Rectangle intersect(Rectangle rect) {
 		int x2 = Math.min(x + width, rect.x() + rect.width());
 		int y1 = Math.max(y, rect.y());
 		int y2 = Math.min(y + height, rect.y() + rect.height());
-		if (((x2 - x1) < 0) || ((y2 - y1) < 0)) {
+		if (((x2 - x1) <= 0) || ((y2 - y1) <= 0)) {
 			return setBounds(0, 0, 0, 0); // no intersection
 		}
 		return setBounds(x1, y1, x2 - x1, y2 - y1);
@@ -739,12 +739,9 @@ public Rectangle intersect(Rectangle rect) {
 	 * @since 2.0
 	 */
 	public boolean intersects(Rectangle rect) {
-		int x1 = Math.max(x, rect.x());
-		int x2 = Math.min(x + width, rect.x() + rect.width());
-		int y1 = Math.max(y, rect.y());
-		int y2 = Math.min(y + height, rect.y() + rect.height());
-
-		return (((x2 - x1) > 0) && ((y2 - y1) > 0));
+		return width > 0 && height > 0 && rect.width() > 0 && rect.height() > 0 //
+				&& x < rect.x() + rect.width() && rect.x() < x + width //
+				&& y < rect.y() + rect.height() && rect.y() < y + height;
 	}
 
 	/**