bob@odi.COM (Bob Miner) (10/16/90)
XtAppMainLoop() seems to be over-writing part of a c++ class instance.
Here are the details:
---------
Create an instance of class Class1.
Constructor of Class1 creates an athena command widget.
Set callback for command widget to be another method in this class.
If this is a non-static method, I believe this is your problem. The
callback has no way to know which object is the 'this' object, hence it's
calling the callback method with a null this. Hence the values for this
are bad, as you saw.
A better approach is to make all your callback methods static methods
and stuff a pointer to your C++ object into the widget's resources (most
widgets have something like a XxNuserData resource). When the static
callback method is called, get the XxNuserData resource from the
widget, cast it to the appropriate C++ type and call a method on
that object to handle the event.
Constructor of Class1 creates an instance of Class2.
Constructor of Class2 initializes one of its slots to zero.
Class1 constructor then continues.
Print class2.slotvalue --> value is zero (correct).
Call XtAppMainLoop(application_context);
End of Class1 constructor (I know it enters an infinite loop before
it gets to "the end" of constructor).
[... stuff deleted ...]
Help...?
--
-----------------------------------
Bill Patterson
pattersw@turing.cs.rpi.edu
Computer Science Department
Rensselaer Polytechnic Institute
Troy, NY.
"Jane, you ignorant slut."
-----------------------------------
Bob Miner
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Object Design, Inc. ~ OOOOOO
1 New England Executive Park ~ OOOO OOOO
Burlington, MA 01803 USA ~ OOOOO OOOOO
bob@odi.com -or- uunet!odi!bob ~ OOOO OOOO
voice: (617) 270-9797 FAX: (617) 270-3509 ~ OOOOOO bject Design Inc.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"From there to here, from here to there, funny things are everywhere."
- Dr. Seuss
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~