DiscoverL Finds the right application id to be started and returns it. First checks if TEditorParameters.iSpecialAppId is set. If it is, returns that. Then connects RApaLsSession and initializes it with GetServerApps command. Then gets all the services that implement the service by using GetServiceImplementationsLC. Calls TryMatchL for each service and if there's a match, the appId is returned. If no implementation is found, 0 is returned.

TryMatchL (Internal) If TEditorParameters.iFlags has either EMsgReadOnly or EMsgPreviewMessage bit set, this function looks for a service that implements the KMsgServiceView part of the service. Otherwise looks for KMsgServiceEdit part. Reads the parameters ( service type (View/Edit), MtmType) from the opaque data. If type and mtm match, sets aAppUi as the application id and returns ETrue. If not found, returns EFalse.