Improve docs about subclassing

- fix syntax errors in example code, e.g.: children_ is private
- use FLTK coding style
- improve alignment

documentation/src/subclassing.dox

@@ -118,16 +118,16 @@ see what parts of your widget need redrawing.</I> The \p handle()
 method can then set individual damage bits to limit the amount of drawing
 that needs to be done:
 \code
-MyClass::handle(int event) {
-  ...
+  int MyClass::handle(int event) {
+    // ...
     if (change_to_part1) damage(1);
     if (change_to_part2) damage(2);
     if (change_to_part3) damage(4);
   }
 
-MyClass::draw() {
+  void MyClass::draw() {
     if (damage() & FL_DAMAGE_ALL) {
-    ... draw frame/box and other static stuff ...
+      // ... draw frame/box and other static stuff ...
     }
 
     if (damage() & (FL_DAMAGE_ALL | 1)) draw_part1();
@@ -416,14 +416,16 @@ that a child needs to be drawn. It is fastest if you avoid
 drawing anything else in this case:
 
 \code
-int MyClass::draw() {
+void MyClass::draw() {
   Fl_Widget *const*a = array();
   if (damage() == FL_DAMAGE_CHILD) { // only redraw some children
-    for (int i = children(); i --; a ++) update_child(**a);
+    for (int i = children(); i--; a++) {
+      update_child(**a);
+    }
   } else { // total redraw
-    ... draw background graphics ...
+    // ... draw background graphics ...
     // now draw all the children atop the background:
-    for (int i = children_; i --; a ++) {
+    for (int i = children(); i--; a++) {
       draw_child(**a);
       draw_outside_label(**a); // you may not need to do this
     }