How to center the main Application Window in MOTIF in the middle of the computer screen? - motif

Question

How to center the main application window of a MOTIF Widget in the center of the computer screen ? for example a form Widget here.
The code is ready and working but the window appears on the left upper side on the screen.
#include <Xm/Form.h>
#include <Xm/Label.h>
#include <Xm/PushB.h>
void main ( int argc, char ** argv )
{
Widget shell, form, label, button;
XtAppContext app;
int i;
shell = XtAppInitialize ( &app, "Formtest", NULL, 0,
&argc, argv, NULL, NULL, 0 );
form = XtCreateManagedWidget ( "form", xmFormWidgetClass,
shell, NULL, 0 );
XtVaSetValues ( form,
XmNwidth, 500,
XmNheight, 300,
NULL );
label = XtVaCreateManagedWidget ( "label", xmLabelWidgetClass,
form, NULL, 0 );
button = XtVaCreateManagedWidget ( "button", xmPushButtonWidgetClass,
form,
XmNbottomAttachment, XmATTACH_FORM,
0 );
XtVaSetValues ( button,
XmNwidth, 100,
XmNheight, 50,
NULL );
XtRealizeWidget ( shell );
XtAppMainLoop ( app );
}`````
This MOTIF Windows is working correct already.
The only thing i want to do is to position it in the middle of the computerscreen.
It has something to do with the command Xtscreen.

Answer 1

Get the Screen height and width and do your adjustments.
Try the following:
#include <Xm/Form.h>
#include <Xm/Label.h>
#include <Xm/PushB.h>
int main ( int argc, char ** argv )
{
Widget shell, form, label, button;
XtAppContext app;
int i;
shell = XtAppInitialize ( &app, "Formtest", NULL, 0,
&argc, argv, NULL, NULL, 0 );
Screen * s = XtScreen(shell);
int dw = WidthOfScreen(s);
int dh = HeightOfScreen( s );
Dimension px = (dw-500)/2;
Dimension py = (dh-300)/2;
XtVaSetValues ( shell,
XmNwidth, 500,
XmNheight, 300,
XmNx, px,
XmNy, py,
NULL );
form = XtCreateManagedWidget ( "form", xmFormWidgetClass,
shell, NULL, 0 );
label = XtVaCreateManagedWidget ( "label", xmLabelWidgetClass,
form, NULL, 0 );
button = XtVaCreateManagedWidget ( "button", xmPushButtonWidgetClass,
form,
XmNbottomAttachment, XmATTACH_FORM,
0 );
XtVaSetValues ( button,
XmNwidth, 100,
XmNheight, 50,
NULL );
XtRealizeWidget ( shell );
XtAppMainLoop ( app );
}