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Help / WLanguage / WLanguage functions / Standard functions / Process functions / Threads, semaphores, signals and mutex
  • Endless wait
  • Synchronizing threads
  • Miscellaneous
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Stored procedures
ThreadWaitSignal (Function)
In french: ThreadAttendSignal
Locks the current thread until it receives a signal from another thread. This function simplifies the synchronization between threads without having to implement an advanced management of events.
  • This function is equivalent to EventWait with an automatic event for a signal sent by ThreadSendSignal. Therefore, the event is automatically closed.
  • Blocking stops immediately (without waiting for the maximum duration) if a request to stop thread is made by another thread using the ThreadRequestStop function.
  • A thread is a process run in parallel with the current application (main thread). This allows you to run a task in the background (e.g. backup, etc.).
  • ThreadWaitSignal and ThreadSendSignal are used to synchronize the threads two by two.
// Create an event
EventCreate("Let's go", eventManual, eventClose)
// Run a first thread
ThreadExécute("Thread1", threadNormal, "Thread_First")
// Locks the current thread until the event is obtained

// Run a second thread
ThreadExécute("Thread2", threadNormal, "Thread_Second")
// Locks the current thread until the event is obtained

// Modifies the event to run the threads
EventChange("Let's go", eventOpen)
PROCÉDURE Thread_First()
Trace(dbgInfo(dbgProcess) + " - ThreadSendSignal(threadMain)")
EventWait("Let's go")
Trace(dbgInfo(dbgProcess) + " - Event received")
PROCÉDURE Thread_Second()
Trace(dbgInfo(dbgProcess) + " - ThreadSendSignal(threadMain)")
EventWait("Let's go")
Trace(dbgInfo(dbgProcess) + " - Event received")
<Result> = ThreadWaitSignal([<Maximum duration>])
<Result>: Boolean
  • True if the current thread received a signal,
  • False if the thread receives no signal (the maximum duration is exceeded).
<Maximum duration>: Optional integer, optional duration or optional constant
Maximum timeout in hundredths of a second.
  • If no signal was received by the thread before the end of specified duration, <Result> is equal to False.
  • If this parameter is not specified or corresponds to the Infinite constant, the wait is infinite.
This parameter can be:
  • an integer corresponding to the number of hundredths of a second,
  • a Duration variable,
  • the duration in a readable format (e.g., 1 s or 10 ms).

Endless wait

You can end the execution of a thread even if it is locked in an endless wait for an event. Simply use ThreadStop.

Synchronizing threads

ThreadWaitSignal and ThreadSendSignal are used to synchronize the threads two by two. To synchronize several threads on the same event, the event management functions must be used:
Remark: The internal mechanisms for managing the queues and stacks allow you not to synchronize the threads (Enqueue and Dequeue for the queues, Push and Pop for the stacks).


ThreadWaitSignal can be used in a process linked to a control (click code of a button, for example): in this case, it is used in the main thread.
Component: wd300vm.dll
Minimum version required
  • Version 9
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Last update: 11/11/2023

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