defaultDevice property

Device? get defaultDevice

What one picture of an entry under this canvas is framed as.

A desktop size is offered, never staged. A phone's screen is a constraint the layout has to survive, so staging it matters; a desktop window has no true size, because the person using it drags the corner. The default stage for a desktop subtree is therefore the resizable one — the plain rectangle, at 1:1 — and the declared window sizes stay in the picker, one click away, for when the question is "does this hold together at 1600 wide".

It is also what you can actually look at. A declared window staged in a panel narrower than itself is scaled down to fit: measured on this GUI, a 1600-wide window in a 490-wide pane is shown at 30%, where type, hairlines and hit targets are all unjudgeable. A preview that cannot be read is not serving its purpose.

The rule costs the case of an app that genuinely wants its big stage on arrival — a kiosk, a wall dashboard. That is one click and it sticks: the picked device rides the address and survives moving between entries.

Implementation

Device? get defaultDevice {
  if (devices.isEmpty) return null;
  var head = devices.first;
  return head.kind == DeviceKind.desktop ? null : head;
}