ArcGIS Engine Developer Guide

C++ APPLICATION PROGRAMMING INTERFACE
3. Manage the widgets.
4. Implement event listening and callback functions for widgets.
5. Display the widgets.
6. Begin the event handling loop.
7. Shut down the application.
To illustrate each of these steps, you will create a simple Motif application.
Motif Program: Simple PushButton
This application will be a single button that displays the number of times the
button was clicked repeatedly to cerr (for example, if double-clicked it will
display “2 clicks”). Start a new file that will be your program. Here that file will
be called pbExample.cpp.
To use the Motif Toolkit you will need to include the Motif header file. The
Motif PushButton widget you will be using requires Xm/PushB.h (each widget’s
header file includes Xm/Xm.h, but it is good practice to include it anyway). For
the display of “pushed”, you will need to include iostream. Xm/Protocols.h will
be used for the callbacks. You will also need a main function. Set these up in your
new file, so that it looks like this:
#include
#include
#include
#include
int main(int argc, char* argv[])
{
return 0;
}
at the top of your new file.
Step 1: Initialize the Motif Toolkit
Your first initialization step is to set the language procedure for Xt. Do so by
calling XtSetLanguageProc. Then you will initialize the Motif Toolkit with a call
to XtVaAppInitialize. This call does a few things: connects the application to the
display; gets any standard command-line arguments; sets up resources; and creates
and returns the top-level window widget, which will be the parent of all other
widgets in this applicaiton.
A deeper understanding of these calls is not necessary to using Motif as it is used
in samples. However, if you would like further information on the parameters
passed into either function, see the Motif Programming Manual resource listed at
the end of this topic.
In ArcGIS Engine applications, you must use
AoInitialize as well, placing the call before any
ArcObjects usage.
The code shown in gray has already been
entered in previous steps. It is given here to
illustrate the accurate placement of the code you
are adding in this step.
int main(int argc, char* argv[])
{
XtSetLanguageProc(NULL, NULL, NULL);
XtAppContext app_context;
Widget topLevel = XtVaAppInitialize(&app_context, "XApplication",
NULL, 0, &argc, argv, NULL, NULL);
Chapter 4 • Developer environments • 235