As a prerequisite, you have to consume the fullscreen contract in the CHIP definition XML.
The fullscreen property is then available in the CHIP API object. It provides the following methods:
You can use this event handler to find out when your CHIP should display a different view, for example when the user switches the fullscreen mode.
You can use this method to find out whether fullscreen mode is on.
You can use this method to switch fullscreen mode from within your CHIP.
var oChipApi = this.getView().getViewData().chip, bIsFullscreen = oChipApi.fullscreen.getFullscreen();