Get actual size of game in screen after cropping (Multi-resolution support)

cocos2d-x C++
#1

After applying the Design Resolution Size and policy how do I get the actual size of the game in the screen ( after the cropping) ?

For example- my design resolution size is (640x360)
I am using the ShowAll policy.
I tried a few different screen sizes and found out the cropping region length. Here, are the findings
1] 480x360 : cropping of 44px above and below the game (contentScalefactor x = 0.75, y = 1.0)
1] 320x240 : cropping of 30px above and below the game (contentScalefactor x = 0.5, y = 0.67)
1] 800x480 : cropping of 15px above and below the game (contentScalefactor x = 1.25, y = 1.33)

I cant seem to figure out the pattern, how the cropping is done. And it does not relate with the contentScaleFactor.
Any ideas?

#2

I may be wrong, but I dont think design resolution changes the screen size, at least this hasn’t been my experience.

Are you doing something like:

cocos2d::CCSize screenSize = pEGLView->getFrameSize();
CCLOG (“screenSize.width %f”, screenSize.width);
CCLOG (“screenSize.height %f”, screenSize.height);

And did you read this: http://www.cocos2d-x.org/projects/cocos2d-x/wiki/Multi_resolution_support