ArcGIS Engine Developer Guide

C++ APPLICATION PROGRAMMING INTERFACE
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.
Step 1: Initialize GTK
Initialize GTK with a call to gtk_init(&argc, &argv);. This call does a few things:
sets up resources, initializes everything needed to work with GTK, and parses
some command-line options.
int main(int argc, char* argv[])
{
gtk_init(&argc, &argv);
}
return 0;
Step 2: Create the widgets
With the toolkit initialized, you can create the single widget you are using in this
application. First you will need to create the window in which you will place the
button. Then you will create the button itself with gtk_button_new_with_label,
since you want a labeled button in this example.
int main(int argc, char* argv[])
{
gtk_init(&argc, &argv);
GtkWidget *window, *button;
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
button = gtk_button_new_with_label("Push the button.");
}
return 0;
Step 3: Place the widgets
For the widgets to show up, they must be added to the main window as follows:
button = gtk_button_new_with_label("Push the button.");
gtk_container_add(GTK_CONTAINER(window), button);
To use multiple widgets in an application, they must be packed. This is done with
horizonal or vertical boxes or panes. Some of the calls related to packing include
gtk_box_pack_start(), gtk_hbox_new(), gtk_vpaned_new(), and
gtk_paned_add1(). Since this example only uses a single widget, this step is not
needed. For additional information on it, see either the reference at the end or
the samples.
Step 4: Implement event listening and callback functions for widgets
You now have a button, but for that to be useful you must hook it to some
functionality. Widgets are attached to behavior at certain events through special
callback functions. You can add callbacks to a widget after it is created.
button = gtk_button_new_with_label("Push the button.");
g_signal_connect(G_OBJECT(button), "button_press_event",
G_CALLBACK(ClickCallback), NULL);
These parameters have the following roles:
• button—the widget that will give off the signal you are watching for.
242 • ArcGIS Engine Developer Guide