Some Tips on Making Application Embeddable

Change App_reg.rss
make embeddability=KAppEmbeddable

To obtain the file name argument we need to override OpenFileL of document class.

To pass an file name argument to such a exe:
TDataType dType(TUid::Uid(EmbedableAppUid));
CDocumentHandler *handler = CDocumentHandler::NewL();
_LIT(KFileName, "c:\data\d.txt");
handler->OpenFileEmbeddedL(KFileName, dType);