Palm OS Programming, 2nd Edition

Application Code for Menus

There’s not a lot of code that needs to be added to support menus. Furthermore, what you do add is straightforward and in some cases standard from application to application. The two routines responsibile for handling menus are:

• MenuHandleEvent

• MyFormHandleEvent

There is also some cookbook code to add that handles the Edit menu; we need to handle the About menu, as well.

MenuHandleEvent

This routine is responsible for handling menu-specific events. Chapter 5 contains a description of MenuHandleEvent and its role within your main event loop. Here is an example found in a main event loop:

do {
   EvtGetEvent(&event, evtWaitForever);
   if (! SysHandleEvent(&event))
      if (! MenuHandleEvent(0, &event, &error))

         if (! ApplicationHandleEvent(&event))
            FrmDispatchEvent(&event);
} while (event.eType != appStopEvent);

MyFormHandleEvent

Your form’s event handler receives an event of type menuEvent if a menu item is chosen. It will commonly have an embedded switch statement to handle each menu item in the form. Here is one such event handler:

static Boolean MyFormHandleEvent(EventPtr event)
{
   Boolean     handled = false;

   switch (event->eType)
      {
         /* other event types */
      case menuEvent:
         switch (event->data.menu.itemID) {
         case MenuItem1:
           // Code to handle MenuItem1.
           handled = true;
           break;

          case MenuItem2:
            // Code to handle MenuItem2.
            handled = true;
            break;
         }
         break;
      }
   return handled;
}

Handling Items in the Edit Menu

The good news about the Edit menu is that the OS already has code ...