ti.map module: change the size of the map according to the delta

Hello, I need to display a portion of the map indicating the current position and the delta. I would like the size of the map would change according to the delta. For example, if I have:

// tss
"# mapview": {
    maptype: Alloy.Globals.Map.NORMAL_TYPE, 
    height: "200dp" 
} 
 
// js
$. mapview.setRegion ({
    latitude: 45.54, 
    longitude: 9:54, 
    latitudeDelta: 0.5, 
    longitudeDelta: 0.5 
});