why does callbak function exist?

Question

what's a callback function and when we should use them?

Does this answer your question? [What is a callback function?](https://stackoverflow.com/questions/824234/what-is-a-callback-function) — Isaiah, Mar 23 '20 at 00:51

score 1 · Accepted Answer · answered Mar 22 '20 at 15:19

A callback is a function you can pass to the framework (in this case Blender). The framework has the control and does some stuff. Now, whenever appropriate, the framework (Blender) calls (executes it with given parameters) this function. Therefore control is given back to your code.

(fictional) Example: Handover a function that prints a text, say

void test() 
{
    std::cout << "Got called back!" << std::endl;
}

There will be some means of registering it, let's say

onRenderCallback(test);

Now, whenever Blender is rendering it will execute test and therefore print "Got called back!".

Commonly, the function takes some argument. This can be used for mouse-input or similar. For example, you could register a function that on any keypress takes the key code and does something with it.

Callbacks are especially useful in the context of the observer-pattern.

why does callbak function exist?

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