Auto-stretching behavior on Mobile Preview Screen

[ghalestrilo]

Nature of issue?

• Existing feature enhancement

Feature enhancement details:

Following discussion from #1472 , we have to decide on a sizing behavior for the sketch rendering canvas in mobile mode. Should it auto-stretch (cover), fit within screen dimensions (contain) or overflow?

@catarak suggested we initialize the sketch with full-screen dimensions, and let the user change at own will, but we don't know how confusing that may be to users

[catarak]

Even though it's ugly, I think the least confusing thing to do is to have the canvas overflow. When a user is working on a sketch, I think they will want to know what it actually looks like on different devices.

I think it would be rad, if possible, to change the default sketch.js if a user creates a new sketch on mobile. I looked at the Processing iOS app and by default, on a p5.js the size of the canvas is widthWidth, windowHeight. I imagine there would be some JS that detects the size of the screen and adjusts the default sketch.js accordingly.