add some comments

java/2-9-HitTest/TransformHittest.java

@@ -31,8 +31,8 @@ class Canvas extends JComponent {
 
     Point M = new Point(); // mouse point
 
-    AffineTransform AT1;
-    AffineTransform AT2;
+    AffineTransform AT1;    // transform matrix for shape1
+    AffineTransform AT2;    // transform matrix for shape2
 
     
     // the house shape (model position is centred at top left corner)
@@ -47,13 +47,12 @@ class Canvas extends JComponent {
 
     Canvas() {
         
-        // create transformation matrices 
+        // create transformation matrix for shape1
         AT1 = new AffineTransform();
         AT1.translate(350, 100);
         AT1.rotate(Math.toRadians(30));
-        AT1.scale(1, 1);
 
-        // create another transformation matrices 
+        // create another transformation matrix for shape2
         AT2 = new AffineTransform();
         AT2.translate(200, 300);
         AT2.rotate(Math.toRadians(30));
@@ -84,47 +83,50 @@ class Canvas extends JComponent {
         g2.drawPolygon(shape.xpoints, shape.ypoints, shape.npoints);
         
 
-        // Transformed Shape 1                
+        // Shape1                
         g2.setTransform(AT1);    // Use Transform Matrix AT1 for shape1
         g2.setColor(Color.RED);  
         g2.drawPolygon(shape.xpoints, shape.ypoints, shape.npoints);
-        // hit test
+
+        // hit testing
         Point MT = new Point();
         try{
+            // create an inverse matrix of AT1
             AffineTransform IAT1 = AT1.createInverse();
+            // apply the inverse transformation to the mouse position
             IAT1.transform(M, MT);
+            // check if original shape contains transformed mouse position
             if (shape.contains(MT.x, MT.y))
                 g2.setColor(Color.RED);
             else
                 g2.setColor(Color.WHITE);  
-
+            g2.fillPolygon(shape);
         } catch (NoninvertibleTransformException e){
             // error
         }
-        g2.fillPolygon(shape);
 
-
-        // Transformed Shape 1        
+        // Shape2
         g2.setTransform(AT2);    // Use Transform Matrix AT2 for shape2
         g2.setColor(Color.BLUE);  
         g2.drawPolygon(shape.xpoints, shape.ypoints, shape.npoints);
         // hit test
         try{
+            // create an inverse matrix of AT2
             AffineTransform IAT2 = AT2.createInverse();
+            // apply the inverse transformation to the mouse position
             IAT2.transform(M, MT);
+            // check if original shape contains transformed mouse position
             if (shape.contains(MT.x, MT.y))
                 g2.setColor(Color.BLUE);
             else
                 g2.setColor(Color.WHITE);  
+            g2.fillPolygon(shape);
         } catch (NoninvertibleTransformException e){
             // error
         }
-        g2.fillPolygon(shape);
         
         // reset to transform 
         g2.setTransform(ATG);
         
     }
-
-
 }