interface/wx/snglinst.h

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