Motif and C++

I am trying to figure out Motif using C++.  I am having a difficult time getting callbacks to work.  I imagine there is some goofy pointer thing happening but I am not sure what.

I have a class MainMenu.  In that class I create some xmPushButtonGadgets.  Now I am trying to set up a call back
here is some code snippets
---
//MainMenu.h
...
protected:
void open(Widget, XtPointer, XtPointer);
...
------
//MainMenu.C

... Widget button;
  button=XtVaCreateManagedWidget("Open",xmPushButtonGadgetClass,_filePullDown,NULL);
  XtAddCallback(button,XmNactivateCallback,&MainMenu::open,NULL);
...

I can not figure out what to pass in for the callback function name.  Everything I have tried generates some goofy error.  This generates the following error

"MainMenu.c++", line 67: error(3252): argument of type
          "void (MainMenu::*)(Widget, XtPointer, XtPointer)" is incompatible
          with parameter of type
          "XtCallbackProc)(Widget, XtPointer, XtPointer)"
    XtAddCallback(button,XmNactivateCallback,&MainMenu::open,NULL);

Thanks

Thought you might be interested to know that I can rack up all the points I want in the advertiser quiz thing by just hitting the back button.
micahAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

lockhartCommented:
You may need to typecast your callback to be an XtCallbackProc. This is a C++ thing, in C it wouldn't particularly care. You also don't need the "&" before your routine name. By definition, a routine name is an address if it isn't followed by parens just like a class name is considered to be a type declaration for an instance if it isn't followed by parens.

Just removing the "&" may reduce this to a warning, but something like:

XtAddCallback (button,
               XmNactivateCallback,
               (XtCallbackProc)MainMenu::open,
               NULL);

will probably let the compiler stick the proper address into the activate callback slot.

Mike
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
jos010697Commented:
If you want a nice C++ environment for Motif, mail
rvloon@xs4all.nl or ronald@and.nl. He's the maintainer
of the Motif++ layer. (there's a mailinglist for this stuff too)

kind regards,

Jos aka jos@and.nl (yes, ronalds desk is opposite of mine ;-)
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
System Programming

From novice to tech pro — start learning today.