Inside Macintosh: Interapplication Communication /

Chapter 4 - Responding to Apple Events

Interacting With the User

When your application receives an Apple event, it may need to interact with the user. For example, it may need to display a dialog box asking the user for additional information or confirmation. You must use the AEInteractWithUser function to make sure your application is in the foreground before it actually interacts with the user.

Both the client application and the server application specify their preferences for user interaction. The AEInteractWithUser function checks the user interaction preferences set by each application. If both the client and the server allow user interaction, AEInteractWithUser usually posts a notification request, and the Notification Manager brings the server to the foreground after the user responds to the notification request.

The AEInteractWithUser function can also bring the server application directly to the foreground, but only if the client application is the active application on the same computer and has set two flags in the sendMode parameter of the AESend function: the kAEWaitReply flag, which indicates that it is waiting for a reply, and the kAECanSwitchLayer flag, which indicates that it wants the server application to come directly to the foreground rather than posting a notification request.

To specify its preferences for how the server application should interact with the user, the client application sets various flags in the sendMode parameter to AESend. The Apple Event Manager sets the corresponding flags in the keyInteractLevelAttr attribute of the Apple event.

The server application sets its preferences with the AESetInteractionAllowed function. This function lets your application specify whether it allows interaction with the user as a result of receiving an Apple event from itself; from itself and other processes on the local computer; or from itself, local processes, and processes from another computer on the network.

Your application calls the AEInteractWithUser function before interacting with the user. If AEInteractWithUser returns the noErr result code, then your application is currently in the front and free to interact with the user. If AEInteractWithUser returns the errAENoUserInteraction result code, the conditions didn't allow user interaction and your application should not interact with the user.

The rest of this section explains how to set user interactions for the client and server applications and the practical effect these settings have when a server needs to interact with a user.

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Subtopics

Setting the Client Application's User Interaction Preferences

Setting the Server Application's User Interaction Preferences

Requesting User Interaction