How to listen for application close (X) event on PC

[NgVThangBz]

i need to free my data before closing my app before the app is closed by (X),
so how can i listen to the app close event.
i used glView->windowShouldClose(), however it doesn't seem to be what i want,

and is it possible to block the close event, I want to show a message "do you want to close the app?" before the app is closed on PC

[rh101]

Have you tried using the GLViewImpl::EVENT_WINDOW_CLOSE event?

[NgVThangBz]

yes i just tried it, and it works fine, thank you.

[NgVThangBz]

So, is it possible to block the application close event?

[rh101]

If you search the code for the event, you'll see that it is sent out from here:

void GLViewImpl::onGLFWWindowCloseCallback(GLFWwindow* window)
{
    bool isClose = true;
    Director::getInstance()->getEventDispatcher()->dispatchCustomEvent(GLViewImpl::EVENT_WINDOW_CLOSE, &isClose);
    if (isClose == false)
    {
        glfwSetWindowShouldClose(window, 0);
    }
}

It passes a pointer to a bool, which is used to control if it should proceed with the closure of the window. So, if you set it to false, it should stop the window from closing. For example:

_eventListener = Director::getInstance()->getEventDispatcher()->addCustomEventListener(GLViewImpl::EVENT_WINDOW_CLOSE,
    [this](EventCustom* e) {
        if (someConditionToStopClosure) 
        {
            const auto close = static_cast<bool*>(e->getUserData());
            *close = false; // Don't allow the window to close
        }
    });

[NgVThangBz]

it works fine, thank you.

[rh101]

Just a side note, and if I understand your issue correctly, I feel that this is not the right solution. If the application is crashing on exit, then you need to find out exactly why, and address the issue accordingly.

If you are getting crashes on exit because of the order of items being deleted, then that is what you need to focus on. Fixing the issue by waiting for the window to close is just a band-aid solution, if that. It may be a sign of a bigger issue in the code.

[NgVThangBz]

when i close the application on pc. it will cause an error if the custom obj still exists,
when my custom obj is released by the system, it will release the other variables (text, sprite, button...).
however this variable was destroyed before, which leads to a crash,
i released my custom obj before the (text, sprite, button...) were released by the system

[rh101]

That's actually a straightforward issue to fix, because you know exactly what is causing it.

If your object holds references to Axmol nodes (or any engine ax::Object instance), then it must call retain(), and also call release() when it is no longer required. That reference must also to nullptr once it's released, so you can check for it (the macro AX_SAFE_RELEASE_NULL does both).

Your custom object should be deleting (or releasing) all references in its destructor. If this is done, then you should not be having any issues at all. You haven't shared any code, so I'm only guessing what would be causing this, but it's always something along these lines.