The picture in the window is the output, not a preview of it.
What is on your screen is exactly what a projector receives. A rehearsal is just the same picture before the room is looking, which means what you approve at the desk is what plays.
Fullscreen
f, or the fullscreen control.
- With a second display connected, the picture goes there, chrome-free and cursor-free, while the controls stay on your laptop.
- With only one display, macOS gives it a Space of its own. Swipe back and forth between the stage and the controls.
Esc or f again closes it.
Letterboxed, never stretched
A 16:9 show on a 16:10 projector gets bars, not distortion. Circles stay circles on somebody else's hardware, which you will not get to check until you are already there.
Output size
Uncapped, in every edition. Output renders at your screen's own size - 4K included. No tier and no build of Sialk degrades the picture; the only limit is an 8K engineering ceiling.
A heavy layer does not slow the show
The compositor draws the last frame it received from each layer. A sketch that can only manage 12 fps updates less often; everything else keeps moving at full rate, and the output does not drop with it.
This is worth knowing when you are deciding whether a sketch is "too heavy". The question is not whether it hits 60, it is whether it looks right at the rate it does hit, next to layers that do.
The two numbers on each layer card - 2448/2448, frames painted against frames
delivered, are how you see this happening. See layers.
A separate output preview
A picture that can differ from what is on the wall, for cueing something up before showing it, arrives at v4.