The visual viewport's size and offset, re-rendering as it changes. null on the server, in a
browser without window.visualViewport, or while enabled is false.
Parameters
enabled: boolean = true
Subscribe only while true; a component that needs the rect in one configuration
(the studio with its formula bar at the bottom) pays nothing in the others.
The signal behind a chrome that must stay above the virtual keyboard: the rect's height is the
room left once the keyboard is up, and offsetTop is how far the browser has moved the visible
part under a layout that did not shrink.
The visual viewport's size and offset, re-rendering as it changes.
nullon the server, in a browser withoutwindow.visualViewport, or whileenabledisfalse.