Some of the buttons on Scribble’s toolbar already work, as you saw when you built Scribble following Step 1, in the previous lesson. The buttons for opening and saving files are already connected to handlers defined by the framework. To make the file operations functional, you wrote the serialize functions for the document and the stroke data structure. Also, the print button is supported by default, and the About button automatically displays the About box for Scribble (the About box was created for you by AppWizard).
The Cut, Copy, and Paste buttons on the toolbar appear grayed, because they have no handlers defined for them. These buttons will not be implemented for Scribble, and so you will (optionally) remove them from the Scribble toolbar.