I am dragging the rectangle representing the built-in screen along the bottom edge of the external screen…
…where does the number 814 come from?
Shouldn’t it be 2560-1920=640 at this point?
It comes from
2560 - (1920 * (10/11)) ≈ 814
because your bottom display is scaled to 110%.
OK, thank you. I think it’s wrong, but I get the explanation. Regardless of what I am about to write, thank you!
Which part I get:
When you’re scaling stuff up, yes, you are spreading the virtual pixels over your physical pixels more generously/wastefully, thus you’re getting fewer virtual pixels. So yes, one could say you’re shrinking your screen down.
Why I think it is wrong:
When arranging the display layout you’re trying to express how your PHYSICAL devices are positioned relatively to each other. I.e. you’re not scaling the screen, you’re scaling the content displayed.
Yeah to be honest I’m not sure if I’m tricking myself into believing the equation I gave because I’m too lazy to think through it properly… but I will now think about it
If we imagine you had two identical monitors, one being scaled to 200%,
M1: 2560x1440
M2: 2560x1440 * 1/2 == 1280x720
then it would make sense to show M2 as half the width in the diagram you posted. Positioning both monitors to be left-aligned, M1 above M2, we would expect the x-coordinate of both monitors to be 0 and a diagram looking like ▛
If we then move M2 rightwards by 1280 pixels, the diagram would appropriately result in the shape ▜
In example one, a cursor moving up through the top left corner of M2 would appear on the bottom left of M1. However in example two, the same cursor moving up through the top left corner of M2, will now originate in the centre of M1.
In each case, the computer has to know which of these virtual placements are desired, and since we are working with virtual space, there is no guarantee that any physical positioning will align, unless the user does this work themselves. Thus, it makes sense for the computer and this layout to work in virtual pixels rather than physical ones.
I do think it seems counter intuitive at first glance though! I only managed to convince myself by writing out this reply x)