How to limit only one application instance in the same machine

I want to control there is one only application run in my machine
I know with Qt3 , we can implement this with QtSingleApplication class
But As for Qt4.3.2, how to do this.

Any guys give me some advice is appreciated!

Thanks

Isnt that class available in Qt 4 series ??

I guess its available only in Commercial edition of Qt

Yes , I am sure this class is not exist in Qt 4.3.2
my version is commercail version

I found more as on way..

one is subclass QApplication

Code:

---

/* target find if bool Apps_Open become true */
windowTitle = QString ( "Layer edit sample" );
Apps_Open = false;    /* default not open */
const QString single_key = QString("ID 29385129512818123 by %1").arg(windowTitle);
 
#if defined Q_WS_WIN
    m_mutex = (void *) CreateMutexW( 0, false, (LPCWSTR) single_key.utf16() );
	  m_prevInstance = ( GetLastError() == ERROR_ALREADY_EXISTS );
    if (m_prevInstance) {
    Apps_Open = true;
    }
 #endif
 
#ifdef Q_OS_UNIX
    unix_sock = make_local_app_socket();
    Apps_Open = unix_sock == 0 ?  true :  false;
    qDebug() << "### sock connect res " << Apps_Open << unix_sock;
 #endif
 
/* on destroy  ~QApplication  remove  socked file  */

---

unix socked connect function ...

Code:

---

#ifdef Q_OS_UNIX
#include <stddef.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/un.h>
 
/* Unix SOCKET to comunicate on parent apps friend and send file or other msg! */
#define _UNIX_SOCKET_ "/tmp/layeres.sock"
 
 
int  make_local_app_socket()
{
    struct sockaddr_un name;
    int sock;
    size_t size;
    sock = socket (PF_LOCAL, SOCK_DGRAM, 0);
       if (sock < 0)
         {
           return 0;
         }
    name.sun_family = AF_LOCAL;
    strncpy (name.sun_path, _UNIX_SOCKET_, sizeof (name.sun_path));
    name.sun_path[sizeof (name.sun_path) - 1] = '\0';
    size = (offsetof (struct sockaddr_un, sun_path) + strlen (name.sun_path) + 1);
 
       if (bind (sock, (struct sockaddr *) &name, size) < 0)
         {
           return 0;
         }
    return sock;
}
#endif

---

Focus to preview apps if is Apps_Open having true

Code:

---

/* focus preview process ! */
bool FocusInstance() const
{
  #if defined Q_WS_WIN
	HWND hWnd = FindWindowW( 0, (LPCWSTR) windowTitle.utf16() );
	if( hWnd )
	{
		long id = GetWindowThreadProcessId( hWnd, 0 );
		AttachThreadInput( id, 0, true );
		if ( IsIconic( hWnd ) )
    ShowWindow( hWnd, SW_RESTORE );
		SetForegroundWindow( hWnd );
		AttachThreadInput( id, 0, false );
		return true;
	}
  #endif
  #ifdef Q_OS_UNIX
  QFileInfo sockets(QString(_UNIX_SOCKET_));
  qDebug() << "### having " << sockets.exists();
        if (unix_sock == 0) {
        qDebug() << "### send file to socket parent here... ";
        return true;
        }
  #endif
	return false;
}

---

All in one ...

http://fop-miniscribus.googlecode.co...wEdit/main.cpp


On mac i not having a solution
IMO one commercial QT version a QtSingleApplication is inside ... but i not know if you can send file or message to the open apps by unix socked is possibel

http://www.google.com/codesearch having a copy of sample commercial "QtSingleApplication"

Cool !
Thanks patrik08

hi patrik08
Are you sure CreateMutexW( ) is Qt's function
for my Qt4.3.2 , I can't find it

It's a Windows function. You have to include <windows.h>.

QtSingleApplication is a solution that commercial customers can obtain from Trolltech (may need an additional fee though). If you are looking for something free and open source, the small class I wrote for use with Edyuk may be of some help to you. It uses local sockets under Mac/Linux and (thanks to a recent contribution) named pipes under windows. A couple of projects (apart from Edyuk ;) ) are already using it as it is lightweight, performant and extremely easy to embed. You can get it by dowloading a recent package of Edyuk (or by doing a SVN checkout).

fullmetalcoder,
Your avatar/icon is NEAT! :)

I'm assuming you are a Linux enthusiast! :D