I have been reading many articles on message mapping from the WndProc function to your own message handlers, and all articles required something either complex or just plain stupid. So, I went about finding a way to implement this in a very easy manner and with as little code as possible. What I came up with satisfies me greatly, and I hope it will satisfy you as well.
The Setup
First off, we need to create the window. I am not going to get into all the code required to do this since there are many other good articles describing each step and giving much better advice on this than I can.
What you need to do is just put a simple line of code into your creation function to allow this whole process to work.
if (hwnd == NULL) {
MessageBox("CreateWindowEx() Failed!", "Debug", NULL, MB_OK);
return false;
}
// Adds a pointer to your current class to the WndClassEx structure
SetWindowLongPtr(hwnd, GWLP_USERDATA, (LONG_PTR)this);
ShowWindow(hwnd, SW_NORMAL);
UpdateWindow(hwnd);
The important line here is:
SetWindowLongPtr(HWND hWnd, int nIndex, LONG_PTR dwNewLong);
All we do is pass in the handle to the window we just created (hwnd, in this case), give it the flag of the parameter we want to change (GWLP_USERDATA, in this case), and finally, the pointer of the class ((LONG_PTR)this - the type cast is required because of the function prototype). This function will allow us to retrieve the pointer to the class at a later time.
Read more: Codeproject
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