It can be used in signal connections but cannot be emitted by the user. Finally, you can use the setHandle function to register a new event object, and the handle function to retrieve the event handle. On a microcontroller, an interrupt tells you when a message has arrived. Set it up so the call to the Windows function blocks until an event occurs, and emit a signal from the thread whenever something happens. But I was kind of confused, how to use them in Qt and now that you mentioned. My post continues unmodified below in case people are using older versions, or if we regain access to the QWinEventNotifier class in the future. Although the class is called QWinEventNotifier , it can be used for certain other objects which are so-called synchronization objects, such as Processes, Threads, Waitable timers.


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Furthermore, inside the slot connected to the notifier’s activated signal, I haven’t been able to find a way to check for available data before calling a read operation. It turns out this is definitely possible to do with Qt.

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QWinEventNotifier Class

Set it up so the call to the Windows function blocks until an event occurs, and emit a signal from the thread whenever something happens. Post as a guest Name.


Then, in a Windows app, you would use WaitForSingleObject or something like that qwiheventnotifier wait for the driver to signal you. Hi Leo, Great news! On Windows the dialog will spin a blocking modal event loop that will not dispatch any QTimers So in other words, it sounds like when getSaveFileName is running, the event loop will temporarily only handle events that belong to the save dialog. Constructs an event notifier with the given parent.



Improving the question-asking experience. A separate polling thread is probably the last resort if there’s no way to get QWinEventNotifier to behave. The docs for the getSaveFileName member function state: This is basically simulating the CAN library signaling when a message is received.

List of All Members for QWinEventNotifier | Qt Core

Just a thought… Doug. That actually makes more sense than qwineventnotfiier way they had it before—after all, it is a private class. I’ve tried checking things like QTextStream. Looks qwinwventnotifier the windows api method PeekNamedPipe as applied to the stdin handle IS able to check for available data! Using this info, you could already solve the problem in a Qt app. Thank you Leo see the comments below for pointing that out! The state of the event is not modified in the process so if it is a manual reset event you will need to reset it after the notification.

Thanks for the example!

Qt Documentation

It was something about the way the functions in the DLL export file were named. Doesn’t really fix the QWinEventNotifier maxing out a cpu thread though.



However, it is generally advisable to explicitly enable or disable the event notifier. Your example is a bit big for me: If the event notifier is enabled, it will emit the activated signal whenever the corresponding event object is signalled. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Downtown Doug Brown » Adding Windows event objects to a Qt event loop

But if I call QFileDialog:: Other than that, the main thread just creates a QWinEventNotifier that receives that qwinevengnotifier. What can I do about this?

You can still use it if you manually grab the private QWinEventNotifier header from the Qt source code and stick it in your program — I just tried it, and it compiled and ran my test program correctly. Thank you for pointing that out. Qt will take care of it from there, qwineventnotifiet you a notification whenever a CAN message is ready for reading.

The setEnabled function allows you to disable as well as enable the event notifier. I create a thread that does nothing other than signal a Windows event object every second or so.