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 Constructor creates a new detached (default) or joinable C++ thread object. It
  30 does not create (or starts execution of) the real thread - for this you should
  31 use \helpref{Create}{wxthreadcreate} and \helpref{Run}{wxthreadrun} methods.
  32
  33 \membersection{wxThread::\destruct{wxThread}}
  34
  35 \func{}{\destruct{wxThread}}{\void}
  36
  37 Destructor frees the ressources associated with the thread. Notice that you
  38 should never delete a detached thread - you may only call
  39 \helpref{Delete}{wxthreaddelete} on it or wait until it terminates (and auto
  40 destructs) itself. Because the detached threads delete themselves, they can
  41 only be allocated on the heap.
  42
  43 The joinable threads, however, may and should be deleted explicitly and
  44 \helpref{Delete}{wxthreaddelete} and \helpref{Kill}{wxthreadkill} functions
  45 will not delete the C++ thread object. It is also safe to allocate them on
  46 stack.
  47
  48 \membersection{wxThread::Create}\label{wxthreadcreate}
  49
  50 \func{wxThreadError}{Create}{\void}
  51
  52 Creates a new thread. The thread object is created in the suspended state, you
  53 should call \helpref{Run}{wxthreadrun} to start running it.
  54
  55 \wxheading{Return value}
  56
  57 One of:
  58
  59 \twocolwidtha{7cm}
  60 \begin{twocollist}\itemsep=0pt
  61 \twocolitem{{\bf wxTHREAD\_NO\_ERROR}}{There was no error.}
  62 \twocolitem{{\bf wxTHREAD\_NO\_RESOURCE}}{There were insufficient resources to create a new thread.}
  63 \twocolitem{{\bf wxTHREAD\_RUNNING}}{The thread is already running.}
  64 \end{twocollist}
  65
  66 \membersection{wxThread::Delete}\label{wxthreaddelete}
  67
  68 \func{void}{Delete}{\void}
  69
  70 Calling \helpref{Delete}{wxthreaddelete} is a graceful way to terminate the
  71 thread. It asks the thread to terminate and, if the thread code is well
  72 written, the thread will terminate after the next call to
  73 \helpref{TestDestroy}{wxthreadtestdestroy} which should happen quiet soon.
  74
  75 However, if the thread doesn't call \helpref{TestDestroy}{wxthreadtestdestroy}
  76 often enough (or at all), the function will not return immediately, but wait
  77 until the thread terminates. As it may take a long time, the message processing
  78 is not stopped during this function execution, so the message handlers may be
  79 called from inside it!
  80
  81 Delete() may be called for thread in any state: running, paused or even not yet
  82 created. Moreover, it must be called if \helpref{Create}{wxthreadcreate} or
  83 \helpref{Run}{wxthreadrun} failed for a detached thread to free the memory
  84 occupied by the thread object (it will be done in the destructor for joinable
  85 threads).
  86
  87 For detached threads Delete() will also delete the C++ thread object, but it
  88 will not do this for joinable ones.
  89
  90 This function can only be called from another thread context.
  91
  92 \membersection{wxThread::Entry}\label{wxthreadentry}
  93
  94 \func{virtual ExitCode}{Entry}{\void}
  95
  96 This is the entry point of the thread. This function is pure virtual and must
  97 be implemented by any derived class. The thread execution will start here.
  98
  99 The returned value is the thread exit code which is only useful for the
 100 joinable threads and is the value returned by \helpref{Wait}{wxthreadwait}.
 101
 102 This function is called by wxWindows itself and should never be called
 103 directly.
 104
 105 \membersection{wxThread::GetId}\label{wxthreadgetid}
 106
 107 \constfunc{unsigned long}{GetId}{\void}
 108
 109 Gets the thread identifier: this is a platform dependent number which uniquely identifies the
 110 thread throughout the system during its existence (i.e. the thread identifiers may be reused).
 111
 112 \membersection{wxThread::GetPriority}\label{wxthreadgetpriority}
 113
 114 \constfunc{int}{GetPriority}{\void}
 115
 116 Gets the priority of the thread, between zero and 100.
 117
 118 The following priorities are defined:
 119
 120 \twocolwidtha{7cm}
 121 \begin{twocollist}\itemsep=0pt
 122 \twocolitem{{\bf WXTHREAD\_MIN\_PRIORITY}}{0}
 123 \twocolitem{{\bf WXTHREAD\_DEFAULT\_PRIORITY}}{50}
 124 \twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
 125 \end{twocollist}
 126
 127 \membersection{wxThread::IsAlive}\label{wxthreadisalive}
 128
 129 \constfunc{bool}{IsAlive}{\void}
 130
 131 Returns TRUE if the thread is alive (i.e. started and not terminating).
 132
 133 \membersection{wxThread::IsDetached}\label{wxthreadisdetached}
 134
 135 \constfunc{bool}{IsDetached}{\void}
 136
 137 Returns TRUE if the thread is of detached kind, FALSE if it is a joinable one.
 138
 139 \membersection{wxThread::IsMain}\label{wxthreadismain}
 140
 141 \func{static bool}{IsMain}{\void}
 142
 143 Returns TRUE if the calling thread is the main application thread.
 144
 145 \membersection{wxThread::IsPaused}\label{wxthreadispaused}
 146
 147 \constfunc{bool}{IsPaused}{\void}
 148
 149 Returns TRUE if the thread is paused.
 150
 151 \membersection{wxThread::IsRunning}\label{wxthreadisrunning}
 152
 153 \constfunc{bool}{IsRunning}{\void}
 154
 155 Returns TRUE if the thread is running.
 156
 157 \membersection{wxThread::Kill}\label{wxthreadkill}
 158
 159 \func{wxThreadError}{Kill}{\void}
 160
 161 Immediately terminates the target thread. {\bf This function is dangerous and should
 162 be used with extreme care (and not used at all whenever possible)!} The resources
 163 allocated to the thread will not be freed and the state of the C runtime library
 164 may become inconsistent. Use \helpref{Delete()}{wxthreaddelete} instead.
 165
 166 For detached threads Kill() will also delete the associated C++ object.
 167
 168 This function can only be called from another thread context.
 169
 170 \membersection{wxThread::OnExit}\label{wxthreadonexit}
 171
 172 \func{void}{OnExit}{\void}
 173
 174 Called when the thread exits. This function is called in the context of the thread
 175 associated with the wxThread object, not in the context of the main thread.
 176
 177 This function should never be called directly.
 178
 179 \membersection{wxThread::Pause}\label{wxthreadpause}
 180
 181 \func{wxThreadError}{Pause}{\void}
 182
 183 Suspends the thread. Under some implementations (Win32), the thread is
 184 suspended immediately, under others it will only be suspended when it calls
 185 \helpref{TestDestroy}{wxthreadtestdestroy} for the next time (hence, if the
 186 thread doesn't call it at all, it won't be suspended).
 187
 188 This function can only be called from another thread context.
 189
 190 \membersection{wxThread::Run}\label{wxthreadrun}
 191
 192 \func{wxThreadError}{Run}{\void}
 193
 194 Starts the thread execution. Should be called after
 195 \helpref{Create}{wxthreadcreate}.
 196
 197 This function can only be called from another thread context.
 198
 199 \membersection{wxThread::SetPriority}\label{wxthreadsetpriority}
 200
 201 \func{void}{SetPriority}{\param{int}{ priority}}
 202
 203 Sets the priority of the thread, between zero and 100. This must be set before the thread is created.
 204
 205 The following priorities are already defined:
 206
 207 \twocolwidtha{7cm}
 208 \begin{twocollist}\itemsep=0pt
 209 \twocolitem{{\bf WXTHREAD\_MIN\_PRIORITY}}{0}
 210 \twocolitem{{\bf WXTHREAD\_DEFAULT\_PRIORITY}}{50}
 211 \twocolitem{{\bf WXTHREAD\_MAX\_PRIORITY}}{100}
 212 \end{twocollist}
 213
 214 \membersection{wxThread::Sleep}\label{wxthreadsleep}
 215
 216 \func{static void}{Sleep}{\param{unsigned long }{milliseconds}}
 217
 218 Pauses the thread execution for the given amount of time.
 219
 220 This function should be used instead of \helpref{wxSleep}{wxsleep} by all worker
 221 (i.e. all except the main one) threads.
 222
 223 \membersection{wxThread::Resume}\label{wxthreadresume}
 224
 225 \func{wxThreadError}{Resume}{\void}
 226
 227 Resumes a thread suspended by the call to \helpref{Pause}{wxthreadpause}.
 228
 229 This function can only be called from another thread context.
 230
 231 \membersection{wxThread::TestDestroy}\label{wxthreadtestdestroy}
 232
 233 \func{bool}{TestDestroy}{\void}
 234
 235 This function should be periodically called by the thread to ensure that calls
 236 to \helpref{Pause}{wxthreadpause} and \helpref{Delete}{wxthreaddelete} will
 237 work. If it returns TRUE, the thread should exit as soon as possible.
 238
 239 \membersection{wxThread::This}\label{wxthreadthis}
 240
 241 \func{static wxThread *}{This}{\void}
 242
 243 Return the thread object for the calling thread. NULL is returned if the calling thread
 244 is the main (GUI) thread, but \helpref{IsMain}{wxthreadismain} should be used to test
 245 whether the thread is really the main one because NULL may also be returned for the thread
 246 not created with wxThread class. Generally speaking, the return value for such thread
 247 is undefined.
 248
 249 \membersection{wxThread::Yield}\label{wxthreadyield}
 250
 251 \func{void}{Yield}{\void}
 252
 253 Give the rest of the thread time slice to the system allowing the other threads to run.
 254 See also \helpref{Sleep()}{wxthreadsleep}.
 255
 256 \membersection{wxThread::Wait}\label{wxthreadwait}
 257
 258 \constfunc{ExitCode}{Wait}{\void}
 259
 260 Waits until the thread terminates and returns its exit code or {\tt
 261 (ExitCode)-1} on error.
 262
 263 You can only Wait() for joinable (not detached) threads.
 264
 265 This function can only be called from another thread context.