autogrow calls resize which is not detecting a need to change size

Hello ,

We have a canvas app hosted on tomcat and viewed from a visualforce page on a record detail page.
For mobile devices, we are using the autogrow function so that the canvas app takes up the whole available space.
The method is not behaving as expected. Autogrow calls resize and resize checks for the scroll height and client height. In our case these values are same. so no resize post message is being sent to the instance and the canvas app remains in it's original size.
It worked when we replaced scroll height with window.screen.height as there is a difference between window screen height and client height.
Can you please let me know why window screen height is not being used ? And also if i am doing something wrong.
I am new to this so be kind :)