https://invisible-island.net/xterm/xtoolkit/
XtAppCreateShell, XtVaAppCreateShell - create top-level widget instance
#include <X11/Intrinsic.h>
Widget XtAppCreateShell(const char *application_name, const char
*application_class, WidgetClass widget_class, Display *display,
ArgList args, Cardinal num_args);
Widget XtVaAppCreateShell(const char * application_name, const char *
application_class, WidgetClass widget_class, Display *display,
...);
application_name
Specifies the name of the application instance.
application_class
Specifies the class name of this application, which usually
is the generic name for all instances of this application.
widget_class
Specifies the widget class that the application top-level
widget should be.
display Specifies the display from which to get the resources.
args Specifies the argument list from which to get the resources.
num_args Specifies the number of arguments in the argument list.
... Specifies the variable argument list from which to get the
resources.
The XtAppCreateShell function saves the specified application name and
application class for qualifying all widget resource specifiers. The
application name and application class are used as the left-most compo-
nents in all widget resource names for this application. XtAppCreate-
Shell should be used to create a new logical application within a pro-
gram or to create a shell on another display. In the first case, it
allows the specification of a new root in the resource hierarchy. In
the second case, it uses the resource database associated with the
other display.
Note that the widget returned by XtAppCreateShell has the WM_COMMAND
property set for session managers (see Chapter 4).
XtCreateWidget(3)
X Toolkit Intrinsics – C Language Interface
Xlib - C Language X Interface
X Version 11 libXt 1.1.5.2 XtAppCreateShell(3)