Q:

Must Cordova app webview take full screen?

A Cordova application as I know it takes full screen of the app. Is there a way to make hybrid UI, I mean some element of the UI is from native code such that the webview doesn't take full screen or when a native UI element lays ontop of the webview in the view stack?

A:

No, it doesn't have to be full size, you can embed the cordova webview on a native project and make it the size you want. And you can mix native parts with the cordova webview.
Take a look into the doc about embedding webviews
http://docs.phonegap.com/en/4.0.0/guide_hybrid_webviews_index.md.html#Embedding%20WebViews
There is another way if you wan't the app to be like a regular cordova project where you can add the plugins with the CLI, you can create a cordova project with the CLI and edit the native code to size the view or change other things. Here you have a two part tutorial about this for iOS:
http://devgirl.org/2014/07/22/mixing-cordova-phonegap-components-with-nativ/
http://devgirl.org/2014/07/24/mixing-cordovaphonegap-components-with-native-ios-part-2/

