General callback on main thread



  • Some time ago I already asked this question, but there was a lot of information and I guess the real question was not really clear. By now I know better what I want:

    Post a(ny) callback on the main thread.

    Can I achieve this somehow? Something like: qApp->postEvent(GeneralCallback) where GeneralCallback could be a global function, the result of for instance std::bind.



  • Hi @Jakob,
    the ad hoc hackish way to implement such system that comes to my mind is:

    • Create an abstract base class AbstractCallback with a virtual 'callback' function
    • Create a class - that inherits AbstractCallback - for each callback function. Add member variables that store the callback arguments and a wrapper function for the actual callback function
    • Post instances of these classes to the event queue
    • Create an event filter that calls the 'callback' functions of those objects


  • @Wieland Thank you for a quick response.

    I was actually thinking along the same directions. Am I correct to assume that such a approach requires me to create a custom event type using QEvent::registerEventType() for the AbstractCallback?

    Additionally, my gut feeling is that creating an event filter on the main event queue (essentially a filter on qApp I presume?) could cause quite some performance loss. Or am I too pessimistic?



  • @Jakob said:

    Am I correct to assume that such a approach requires me to create a custom event type

    Yes.

    [...] could cause quite some performance loss. Or am I too pessimistic?

    Don't know, you'll have to meassure the impact. What I can say is that I used an event filter recently to handle input from a graphics tablet. Processing huge amounts of events in real time was no problem.


Log in to reply
 

Looks like your connection to Qt Forum was lost, please wait while we try to reconnect.