Access instance from callback function

Question

How can I access the class instance inside a GLFW3 input callback function, for example this one.

I want my instance do something when a specific event happens. Each instance might do something different for a specific event.

Specifically, my class has a std::map< int, std::function< void()>>, where a key is mapped to a function.

EDIT: I tried the following, but this gives me an error that it doesn't match the glfwSetKeyCallback function call.

glfwSetKeyCallback(window, [this](GLFWwindow * window, int key, int scancode, int action, int mods){
    addCommand(m_events.at(key));
});

@WhozCraig: Um, sure? I mean, a key is pressed and the corresponding function will be called. — gartenriese
I only asked because "where a function is mapped to a key." seemed the exact opposite of the proposed map immediately before. Just wanted to clarify. — WhozCraig
I always thought it was the other way around. Well, you always learn something new. Thanks! — gartenriese

gartenriese gartenriese · Accepted Answer · 2014-04-04T09:38:19

Taken from here.

You need something like this:

glfwSetWindowUserPointer(window, this);
glfwSetKeyCallback(window, [](GLFWwindow * window, int key, int scancode, int action, int mods){

    Window * win = static_cast<Window *>(glfwGetWindowUserPointer(window));
    win->addCommand(win->m_events.at(key));

});

Access instance from callback function

1 Answers