interface/wx/snglinst.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        snglinst.h
   3 // Purpose:     interface of wxSingleInstanceChecker
   4 // Author:      wxWidgets team
   5 // RCS-ID:      $Id$
   6 // Licence:     wxWindows licence
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 /**
  10     @class wxSingleInstanceChecker
  11
  12     wxSingleInstanceChecker class allows to check that only a single instance of a
  13     program is running.
  14
  15     To do it, you should create an object of this class. As long as this object
  16     is alive, calls to wxSingleInstanceChecker::IsAnotherRunning from other
  17     processes will return @true.
  18
  19     As the object should have the life span as big as possible, it makes sense to
  20     create it either as a global or in wxApp::OnInit.
  21     For example:
  22
  23     @code
  24     bool MyApp::OnInit()
  25     {
  26         m_checker = new wxSingleInstanceChecker;
  27         if ( m_checker-IsAnotherRunning() )
  28         {
  29             wxLogError(_("Another program instance is already running, aborting."));
  30
  31             delete m_checker; // OnExit() won't be called if we return false
  32             m_checker = NULL;
  33
  34             return false;
  35         }
  36
  37         ... more initializations ...
  38
  39         return true;
  40     }
  41
  42     int MyApp::OnExit()
  43     {
  44         delete m_checker;
  45
  46         return 0;
  47     }
  48     @endcode
  49
  50     Note that by default wxSingleInstanceChecker::CreateDefault() is used to
  51     create the checker meaning that it will be initialized differently for
  52     different users and thus will allow different users to run the application
  53     concurrently which is usually the required behaviour. However if only a
  54     single instance of a program should be running system-wide, you need to
  55     call Create() with a custom name which does @em not include wxGetUserId().
  56
  57     This class is implemented for Win32 and Unix platforms (supporting @c fcntl()
  58     system call, but almost all of modern Unix systems do) only.
  59
  60     @library{wxbase}
  61     @category{appmanagement}
  62 */
  63 class wxSingleInstanceChecker
  64 {
  65 public:
  66     /**
  67         Default constructor.
  68
  69         You may call Create() after using it or directly call
  70         IsAnotherRunning() in which case CreateDefault() will be implicitly
  71         used.
  72     */
  73     wxSingleInstanceChecker();
  74
  75     /**
  76         Constructor calling Create().
  77
  78         This constructor does exactly the same thing as Create() but doesn't
  79         allow to check for errors.
  80     */
  81     wxSingleInstanceChecker(const wxString& name,
  82                             const wxString& path = wxEmptyString);
  83
  84     /**
  85         Destructor frees the associated resources.
  86
  87         Note that it is not virtual, this class is not meant to be used polymorphically.
  88     */
  89     ~wxSingleInstanceChecker();
  90
  91     /**
  92         Initialize the object if it had been created using the default constructor.
  93
  94         Note that you can't call Create() more than once, so calling it if the
  95         non default ctor had been used is an error.
  96
  97         @param name
  98             Must be given and be as unique as possible. It is used as the
  99             mutex name under Win32 and the lock file name under Unix.
 100             wxApp::GetAppName() and wxGetUserId() are commonly used to construct
 101             this parameter.
 102         @param path
 103             The path is optional and is ignored under Win32 and used as the
 104             directory to create the lock file in under Unix
 105             (default is wxGetHomeDir()).
 106
 107         @return
 108             Returns @false if initialization failed, it doesn't mean that
 109             another instance is running -- use IsAnotherRunning() to check for
 110             it.
 111
 112         @note
 113             One of possible reasons while Create() may fail on Unix is that the lock
 114             file used for checking already exists but was not created by the user.
 115             Therefore applications shouldn't treat failure of this function as fatal
 116             condition, because doing so would open them to the possibility of a
 117             Denial of Service attack. Instead, they should alert the user about
 118             the problem and offer to continue execution without checking if
 119             another instance is running.
 120     */
 121     bool Create(const wxString& name,
 122                 const wxString& path = wxEmptyString);
 123
 124     /**
 125         Calls Create() with default name.
 126
 127         This method simply calls Create() with a string composed of
 128         wxApp::GetAppName() and wxGetUserId().
 129
 130         Because this method uses wxApp::GetAppName(), it may only be called
 131         after the global application was constructed.
 132
 133         @since 2.9.1
 134      */
 135     bool CreateDefault();
 136
 137     /**
 138         Returns @true if another copy of this program is already running and
 139         @false otherwise.
 140
 141         Notice that if the object was created using the default constructor
 142         Create() hadn't been called before this method, it will call
 143         CreateDefault() automatically.
 144     */
 145     bool IsAnotherRunning() const;
 146 };
 147