Russian Qt Forum

C++ (Qt)
#include <X11/Xlib.h>
 
void showFullScreen( Display* dpy, Window wid )
{
	XWindowAttributes xwa;
	XGetWindowAttributes( dpy, wid, &xwa );
 
	XEvent e;
	e.xclient.type = ClientMessage;
	e.xclient.message_type = XInternAtom( dpy, "_NET_WM_STATE", false );
	e.xclient.display = dpy;
	e.xclient.window = wid;
	e.xclient.format = 32;
	e.xclient.data.l[0] = 1;
	e.xclient.data.l[1] = XInternAtom( dpy, "_NET_WM_STATE_FULLSCREEN", false );
	e.xclient.data.l[2] = 0;
	e.xclient.data.l[3] = 0;
	e.xclient.data.l[4] = 0;
	XSendEvent( dpy, xwa.root,
		false, SubstructureNotifyMask | SubstructureRedirectMask, &e );
}
 

Bash
xprop -root | grep _NET_SUPPORTED | grep _NET_WM_STATE_FULLSCREEN

C++ (Qt)
#include <QApplication>
#include <QLabel>
 
#include <X11/Xlib.h>
#include <QX11Info>
 
void showFullScreen( Display* dpy, Window wid )
{
	XWindowAttributes xwa;
	XGetWindowAttributes( dpy, wid, &xwa );
 
	XEvent e = { 0 };
	e.xclient.type = ClientMessage;
	e.xclient.message_type = XInternAtom( dpy, "_NET_WM_STATE", false );
	e.xclient.display = dpy;
	e.xclient.window = wid;
	e.xclient.format = 32;
	e.xclient.data.l[0] = 1;
	e.xclient.data.l[1] = XInternAtom( dpy, "_NET_WM_STATE_FULLSCREEN", false );
	XSendEvent( dpy, xwa.root,
		false, SubstructureNotifyMask | SubstructureRedirectMask, &e );
}
 
int main( int argc, char** argv )
{
	QApplication app( argc, argv );
	QLabel label( "Hello!" );
	label.setAlignment( Qt::AlignCenter );
	label.show();
 
	showFullScreen( QX11Info::display(), label.winId() );
 
	return app.exec();
}