add toString methods for some graphics classes

src/edu/macalester/graphics/Arc.java

@@ -103,4 +103,9 @@ public Rectangle2D getBounds() {
     protected Object getEqualityAttributes() {
         return shape;
     }
+
+    @Override
+    public String toString() {
+        return "Arc at position " + getX() + ", " + getY() + ", of size " + (int)getWidth() + " by " + (int)getHeight() + " starting at angle " + shape.getAngleStart() + " sweeping through an angle of " + shape.getAngleExtent();
+    }
 }

src/edu/macalester/graphics/CanvasWindow.java

@@ -750,4 +750,9 @@ public void performEventAction(Runnable action) {
             draw();
         });
     }
+
+    public String toString() {
+        return "CanvasWindow of size " + canvas.getWidth() + " by " + canvas.getHeight() +
+                " containing " + content.numChildren() + " GraphicsObjects";
+    }
 }

src/edu/macalester/graphics/GraphicsGroup.java

@@ -132,6 +132,10 @@ public GraphicsObject getElementAtLocalCoordinates(double x, double y) {
         return null;
     }
 
+    public int numChildren() {
+        return children.size();
+    }
+
     @Override
     protected void drawInLocalCoordinates(Graphics2D gc) {
         for (GraphicsObject obj : children) {
@@ -212,6 +216,6 @@ protected Object getEqualityAttributes() {
 
     @Override
     public String toString() {
-        return "A graphics group at position (" + getX() + ", " + getY() + ") with size=" + getSize();
+        return "GraphicsGroup at position (" + getX() + ", " + getY() + ") with size=" + getSize();
     }
 }

src/edu/macalester/graphics/GraphicsText.java

@@ -385,4 +385,9 @@ public Rectangle2D getBounds() {
     protected Object getEqualityAttributes() {
         return List.of(font, text);
     }
+
+    @Override
+    public String toString() {
+        return "GraphicsText at " + getPosition() + " with text '" + text + "'";
+    }
 }