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Mac Forum / Programming / CodeWarrior / July 2004Query re PPx example
I am trying to duplicate some functionality in the PPX TextEditor example -- specifically, that in MyTextDocument.cp (MTD). MTD inherits from Correspondent and CommandHandler<kHICommandClose> contains a Window overrides DoSpecificCommand and ClassName (inter alia) is registered in the main app with the class name The close handler is installed *on the Window* but handler code belongs to MTD. When the window is closed, it is MTD that handles the action. Presumably this is all as it should be but Two questions: 1) How does MTD get into the "containment hierarchy" of the Window? Apple docs, including a picture, seem to contradict this. 2) In trying to duplicate this functionality, I created a dialog, in IB, with OK and Cancel buttons having custom commands. I created a class, Setup, inheriting from Correspondent and CommandHandler (for my custom OK and Close), overrode DoSpecificCommand and ClassName and registered the name just as in TextEditor. I tried installing both on the window and on Setup directly. In both cases, the custom command was not handled until it got to the main app which inherits from CommandConverter. In other words, Setup does *not* seem to be in the containment hierarchy. Can anyone tell what I am doing wrong here? Obviously, this should all be very standard and straightforward but it isn't. TIA. -- Mike McLaughlin > I am trying to duplicate some functionality in the PPX TextEditor > example -- specifically, that in MyTextDocument.cp (MTD). [quoted text clipped - 13 lines] > 1) How does MTD get into the "containment hierarchy" of the Window? > Apple docs, including a picture, seem to contradict this. You need to distinguish between the Event Target and the Event Doer. The two do not have to be the same object. In this case, the Window is the Event Target, and the MTD is the Event Doer. When the system sends the close event to the Window, the system calls the last installed event handler. To the system, and event handler is really just a function pointer. In PPx, the function that the system calls for an event handler is converted into a virtual function call for some Event Doer object. So, the MTD is not in the containment hierarchy of the Window. The MTD installs an event hander on the Window, and the PPx implementation of an event handler callback function results in a call to a virtual function of the MTD. > 2) In trying to duplicate this functionality, I created a dialog, in IB, > with OK and Cancel buttons having custom commands. I created a class, [quoted text clipped - 6 lines] > main app which inherits from CommandConverter. In other words, Setup > does *not* seem to be in the containment hierarchy. When you say "custom command", I assume you mean a command ID with a four-character code that isn't one of Apple's reserved IDs. When the button is clicked, it sends an event with a signature (class, type) of (kEventClassCommand, kEventCommandProcess). If you don't have any custom handlers for that kind of event installed (and you probably don't), then the event percolates up to the PPx Application class, which inherits from CommandConverter. The purpose of CommandConverter is to respond to a (kEventClassCommand, kEventCommandProcess) event by sending a different event, of kind (eventClass_ProcessCommand, "specific command ID") to the user focus target. In your case, "specific command ID' as the four-character code of the button's command ID. I can't tell from the description above how you have installed your event handlers. But, you need to have your Setup class install an event handler on something that is in the user focus chain when the button is clicked. What that "something" is depends on your application. If the button is in a dialog window, then probably the window object. However, if your button is in a floating window which doesn't have the focus, the specific command event will be sent to the window (probably the active document) that does have the focus. If no obvious target comes to mind, you can always install the handler on the application event target. This might be a problem if you have multiple windows that contain buttons with the same command ID. Then, you would need a way to determine which button was sending the command. -- Greg |
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