Writing a test main Fortran application

We need to write the Fortran code to instantiate ActiveX object CMain and handle its events. Let’s start with the function to handle the events, which as with all other procedures in this program is contained in module f90VBGUI (Sample Code 13). Note that we have called this event handler CMainTestEventsHandler. We used this name because this is not the final event handler for our program, but rather a test handler. At this point, all we want is a skeleton of an event handler, so we can concentrate on how things work. We’ll write the real event handler later.

CMainTestEventsHandler is a very simple subroutine. We won’t discuss the declaration or arguments passed to this subroutine because they are fully described in the f90VB User and Reference Manuals. The important part of the code is located inside the subroutine’s select statement. The statement discriminates among different values of variable DispID and prints a message on the console window of the main program. DispID is the dispatch ID number of the events fired by class CMain. Each event fired by an outgoing interface has a unique DispID that can be used to identify the event. You can obtain the DispID of each event in an interface by checking the Attributes tab for the event with TLView. For example, Figure 17 shows that event OnFactorialTableClick has a DispID of 3.

As you might have inferred, subroutine CMainTestEventsHandler will be called by class CMain each time the class fires an event. Remember that most of the events in CMain are fired when the user selects options from the main menu. So when the user selects menu option Tools/Factorials Table…, class CMain fires event OnFactorialTableClick, subroutine CMainTestEventsHandler is called with a DispID of 3, and we print a message on the main program console window saying that this menu option was selected. Likewise, when the user selects About f90VB Demo (DispID=4) from the main menu, rather than print a message we show the About dialog box exposed by class CAbout.

In addition to subroutine CMainTestEventsHandler, you might have noticed that we also added some variables in the declaration section of module f90VBGUI. The reason for this will become obvious later, when we start working on the real event handler subroutine for our program.

Ok, now we have simple function to handle the events fired by object CMain, and we are ready to write a test main application program (program TestCMain). The main application has some compiler-dependent code, so you can select the links below for the compiler of your preference:

Program TestCMain for Absoft Pro Fortran (Sample Code 14a)

Program TestCMain for Compaq Visual fortran (Sample Code 14b)

Program TestCMain for Lahey Fortran 95 (Sample Code 14c)

Let’s dissect the main application program and see what it does. First, we initialize OLE, create an instance of the CMain object and store it in variable CMain:

!Initialize Ole

iRet = OleInitialize()

!Create an instance of the CMain object

CMain = CreateOleObject('f90VBGUI.CMain',iRet)

!Create an instance of the CInput object

CInput = CreateOleObject('f90VBGUI.CInput',iRet)

We also create an instance of CInput. Although CMainTestEventsHandler doesn’t use it, CInput will be used by the final event handler that we’ll write later. If everything goes well, we create an f90VB sink object and connect the object to the CMain instance we created earlier:

EventSinkHndl = EventSinkCreate(iRet)

call EventSinkConnect(EventSinkHndl, CMain, NullGUID() ,iRet)

Note that we use the handle returned by function EventSinkCreate to refer to the specific instance of the f90VB sink object in all subsequent calls. You may have more than one sink object active at any time. Also note that we pass the result of f90VB function NullGUID() to the connection subroutine, which connects the sink object to the default outgoing interface of CMain, in this case __CMain (you can verify this using TLView).

Next, our program registers the events we want to handle. We register the same subroutine CMainTestEventsHandler for all four events we are interested in. Notice that CMain also fires a fifth event (OnQuit), but our program doesn’t need to handle this event.

call EventSinkRegEvnt(EventSinkHndl, 'OnLogTableClick', &