Could you explain this a little more please.

I will expalin it based on default Cocos2d-x IOS Project hello world:

You creating project, launching it in emulator: it is running in Landscape mode. 

https://www.dropbox.com/s/dgucpyka2tlxuhu/iOS%20Simulator%20Screen%20Shot%2021%20Aug%202015%2014.39.07.png?dl=0

Changing file to support Portrait mode;:

RootViewController.mm

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {

    return UIInterfaceOrientationIsPortrait(interfaceOrientation)||UIInterfaceOrientationIsLandscape(interfaceOrientation);

}

Launching app. In Portrait mode half scene is visible on bottom of the screen and top of the screen is black and you can’t place any object on that black area .

https://www.dropbox.com/s/dijfnknzuyxn62a/iOS%20Simulator%20Screen%20Shot%2021%20Aug%202015%2014.43.28.png?dl=0

So  we need somehow resize scene so it should be working after rotation like 1024x768 instead of 768x1024 like guys describing that issue there: http://discuss.cocos2d-x.org/t/trying-to-resize-scene-on-orientation-change/3459

Hope it is more clear, like there is no need to autoamticly reposition all elements of the app, we just need to resize window to fill full phone area in new orientation and then we will place our elements on it.

You mean like candy crush

Yes, like candy crash. 

ok

will do