I tried your instructions in Pharo 1.3 with a direct Subclass of Morph and noticed some differences to your description (which may very well be due to my lack of understanding..):
1) the examples work as well, if you do not add:
handlesMouseDown: anEvent
^ true.
if I did add handleMouseDown, my Morph did loose all other standard mouse actions, like beeing dragable.
2) defaultYellowButtonMenuEnabled
^ true.
had to be included also if you did not want the default menu + some #addCustomMenuItems: aCustomMenu hand: aHandMorph _but also_ if you wanted a complete custom menu with #addYellowButtonMenuItemsTo: aMenu event: evt
Perhaps you have some more information on this?
BTW, thank you very much for the book entry, it’s much appreciated. I am a regular reader of the collaboractive book :)
Best regards, Helene.