A question of function design?

[Mike Parker via Digitalmars-d-learn]

On Friday, 28 October 2016 at 13:19:19 UTC, WhatMeWorry wrote:

>
> Anyone have a good example of what I should be doing?

I generally use GLFW event callbacks to populate an event queue 
with custom event types, then process the queue and handle events 
elsewhere. That way, the callbacks need no nothing at all about 
the game code.

```
void setCallbacks() {
     glfwSetKeyCallback(&key_callback);
}

private:
MyEventQueue _eventq;

extern(C) void key_callback(GLFWwindow* window, int key, int 
scancode, int action, int modifier) {
     eventq.push(KeyEvent(window, key, scancode, action, modifier);
}

An alternative approach is to forego the event queue and just 
have the callbacks process event listeners. The listeners could 
be delegates, function pointers, or interfaces, whatever works 
for your scenario, or some specific event handler class. They 
might be stored in flat arrays, or aas keyed on the window or a 
KeyEvent structure. Whatever works.

```
alias KeyHandler = bool delegate(GLFWwindow, int, int, int, int);
void registerKeyHandler(KeyHandler handler) { _keyHandlers ~= 
handler; }

private:
KeyHandler[] _keyHandlers;

extern(C) void key_callback(GLFWwindow* window, int key, int 
scancode, int action, int modifier) {
     foreach(handler; _keyHandlers) {
         if(_keyHandler(window, key, scancode, action, modifier)) 
break;
     }
}
```