docs/latex/wx/thread.tex

   1 \section{\class{wxThread}}\label{wxthread}
   2
   3 A thread is basically a path of execution through a program. Threads are also
   4 sometimes called {\it light-weight processes}, but the fundamental difference
   5 between threads and processes is that memory spaces of different processes are
   6 separated while all threads share the same address space. While it makes it
   7 much easier to share common data between several threads, it also makes much
   8 easier to shoot oneself in the foot, so careful use of synchronization objects
   9 such as \helpref{mutexes}{wxmutex} and/or \helpref{critical sections}{wxcriticalsection} is recommended.
  10
  11 \wxheading{Derived from}
  12
  13 None.
  14
  15 \wxheading{Include files}
  16
  17 <wx/thread.h>
  18
  19 \wxheading{See also}
  20
  21 \helpref{wxMutex}{wxmutex}, \helpref{wxCondition}{wxcondition}, \helpref{wxCriticalSection}{wxcriticalsection}
  22
  23 \latexignore{\rtfignore{\wxheading{Members}}}
  24
  25 \membersection{wxThread::wxThread}\label{wxthreadctor}
  26
  27 \func{}{wxThread}{\void}
  28
  29 Default constructor: it doesn't create nor starts the thread.
  30
  31 \membersection{wxThread::\destruct{wxThread}}
  32
  33 \func{}{\destruct{wxThread}}{\void}
  34
  35 wxThread destructor is private, so you can not call it directly - i.e., deleting
  36 wxThread objects is forbidden. Instead, you should use \helpref{Delete}{wxthreaddelete} or
  37 \helpref{Kill}{wxthreadkill} methods. This also means that thread objects should
  38 eb {\bf always} allocated on the heap (i.e. with {\it new}) because the functions
  39 mentioned above will try to reclaim the storage from the heap.
  40
  41 \membersection{wxThread::Create}\label{wxthreadcreate}
  42
  43 \func{wxThreadError}{Create}{\void}
  44
  45 Creates a new thread. The thread object is created in the suspended state, you
  46 should call \helpref{Run}{wxthreadrun} to start running it.
  47
  48 \wxheading{Return value}
  49
  50 One of:
  51
  52 \twocolwidtha{7cm}
  53 \begin{twocollist}\itemsep=0pt
  54 \twocolitem{{\bf wxTHREAD\_NO\_ERROR}}{There was no error.}
  55 \twocolitem{{\bf wxTHREAD\_NO\_RESOURCE}}{There were insufficient resources to create a new thread.}
  56 \twocolitem{{\bf wxTHREAD\_RUNNING}}{The thread is already running.}
  57 \end{twocollist}
  58
  59 \membersection{wxThread::Delete}\label{wxthreaddelete}
  60
  61 \func{void}{Delete}{\void}
  62
  63 This function should be called to terminate this thread. Unlike \helpref{Kill}{wxthreadkill}, it
  64 gives the target thread the time to terminate gracefully. Because of this, however, this function
  65 may not return immediately and if the thread is "hung" won't return at all. Also, message processing
  66 is not stopped during this function execution, so the message handlers may be called from inside
  67 it.
  68
  69 Delete() may be called for thread in any state: running, paused or even not yet created. Moreover,
  70 it must be called if \helpref{Create}{wxthreadcreate} or \helpref{Run}{wxthreadrun} fail to free
  71 the memory occupied by the thread object.
  72
  73 \membersection{wxThread::Entry}\label{wxthreadentry}
  74
  75 \func{virtual void *}{Entry}{\void}
  76
  77 This is the entry point of the thread. This function is pure virtual and must
  78 be implemented by any derived class. The thread execution will start here.
  79
  80 The returned value is the thread exit code but is currently ignored in
  81 wxWindows implementation (this will change in near future).
  82
  83 \membersection{wxThread::GetID}\label{wxthreadgetid}
  84
  85 \constfunc{unsigned long}{GetID}{\void}
  86
  87 Gets the thread identifier: this is a platform dependent number which uniquely identifies the
  88 thread throughout the system during its existence (i.e. the thread identifiers may be reused).
  89
  90 \membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
  91
  92 \constfunc{int}{GetPriority}{\void}
  93
  94 Gets the priority of the thread, between zero and 100.
  95
  96 The following priorities are already defined:
  97
  98 \twocolwidtha{7cm}
  99 \begin{twocollist}\itemsep=0pt
 100 \twocolitem{{\bf WXTHREAD\_MIN\_PRIORITY}}{0}
 101 \twocolitem{{\bf WXTHREAD\_DEFAULT\_PRIORITY}}{50}
 102 \twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
 103 \end{twocollist}
 104
 105 \membersection{wxThread::IsAlive}\label{wxthreadisalive}
 106
 107 \constfunc{bool}{IsAlive}{\void}
 108
 109 Returns TRUE if the thread is alive (i.e. started and not terminating).
 110
 111 \membersection{wxThread::IsMain}\label{wxthreadismain}
 112
 113 \constfunc{bool}{IsMain}{\void}
 114
 115 Returns TRUE if the calling thread is the main application thread.
 116
 117 \membersection{wxThread::IsPaused}\label{wxthreadispaused}
 118
 119 \constfunc{bool}{IsPaused}{\void}
 120
 121 Returns TRUE if the thread is paused.
 122
 123 \membersection{wxThread::IsRunning}\label{wxthreadisrunning}
 124
 125 \constfunc{bool}{IsRunning}{\void}
 126
 127 Returns TRUE if the thread is running.
 128
 129 \membersection{wxThread::Kill}\label{wxthreadkill}
 130
 131 \func{wxThreadError}{Kill}{\void}
 132
 133 Immediately terminates the target thread. {\bf This function is dangerous and should
 134 be used with extreme care (and not used at all whenever possible)!} The resources
 135 allocated to the thread will not be freed and the state of the C runtime library
 136 may become inconsistent. Use \helpref{Delete()}{wxthreaddelete} instead.
 137
 138 \membersection{wxThread::OnExit}\label{wxthreadonexit}
 139
 140 \func{void}{OnExit}{\void}
 141
 142 Called when the thread exits. This function is called in the context of the thread
 143 associated with the wxThread object, not in the context of the main thread.
 144
 145 \membersection{wxThread::Run}\label{wxthreadrun}
 146
 147 \func{wxThreadError}{Run}{\void}
 148
 149 Runs the thread.
 150
 151 \membersection{wxThread::SetPriority}\label{wxthreadsetpriority}
 152
 153 \func{void}{SetPriority}{\param{int}{ priority}}
 154
 155 Sets the priority of the thread, between zero and 100. This must be set before the thread is created.
 156
 157 The following priorities are already defined:
 158
 159 \twocolwidtha{7cm}
 160 \begin{twocollist}\itemsep=0pt
 161 \twocolitem{{\bf WXTHREAD\_MIN\_PRIORITY}}{0}
 162 \twocolitem{{\bf WXTHREAD\_DEFAULT\_PRIORITY}}{50}
 163 \twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
 164 \end{twocollist}
 165
 166 \membersection{wxThread::Sleep}\label{wxthreadsleep}
 167
 168 \func{\void}{Sleep}{\param{unsigned long }{milliseconds}}
 169
 170 Pauses the thread execution for the given amount of time.
 171
 172 This function should be used instead of \helpref{wxSleep}{wxsleep} by all worker
 173 (i.e. all except the main one) threads.
 174
 175 \membersection{wxThread::This}\label{wxthreadthis}
 176
 177 \func{wxThread *}{This}{\void}
 178
 179 Return the thread object for the calling thread. NULL is returned if the calling thread
 180 is the main (GUI) thread, but \helpref{IsMain}{wxthreadismain} should be used to test
 181 whether the thread is really the main one because NULL may also be returned for the thread
 182 not created with wxThread class. Generally speaking, the return value for such thread
 183 is undefined.
 184
 185 \membersection{wxThread::Yield}\label{wxthreadyield}
 186
 187 \func{\void}{Yield}{\void}
 188
 189 Give the rest of the thread time slice to the system allowing the other threads to run.
 190 See also \helpref{Sleep()}{wxthreadsleep}.
 191