This is a really dumb question and for some reason I'm totally blanking on it right about now. Inside my main-loop I'd like to have a pointer-to-pointer that points to an Screen-object pointer ( So if the screen pointer is assigned a new object to point towards the pointer-to-pointer is updated along.

However, I'm getting an error when trying to assign my pointer-to-pointer the screen pointer:

Screen* ScreenManager::activeScreen()
{
  return m_screen;
}

Screen** s = &screenManager.activeScreen();

I'm getting the following error:

Error: expression must be an lvalue or function designator

However this works just fine:

Screen* p = screenManager.activeScreen();
Screen** s = &p;

I'm sure this is VERY simple, but I just keep blanking where the problem lies.

Screen** ScreenManager::activeScreen()
{
  return &m_screen;
}

I think you want:

Screen** ScreenManager::activeScreen()
{
  return &m_screen;
}

Is this the way to do it? Because I'd rather avoid returning a pointer-to-pointer seeing as other functions just use a normal pointer.

What do you want to accomplish with a double pointer that you cannot do with a single pointer?

Screen* s = screenManager.activeScreen();

Screen** s = &screenManager.activeScreen();

Error: expression must be an lvalue or function designator

Screen *& ScreenManager::activeScreen() {
  return m_screen;
}

When you return a pointer by value, you get a copy of the pointer. There is just no way to use a copy of an object to get the address of the original object. A copy is a brand new object with no address information of the original object. You need to either return the address of the object in the first place (the Screen ** approach) or a reference to the original object (the Screen *& approach).

Copy of the object? I'm guessing the object you are referring to is the pointer copy ( pointers are objects as well I guess ).

But then why does assigning it to a normal pointer THEN assigning that pointer to a pointer-to-pointer work?
Is it because the pointer copy still refers to the same value address so the "original" pointer gets the pointer-copys values adress then we the pointer-to-pointer can get the "original" pointers adress?

Is it something like that?