[R103] Error setting X & Y position in crop mode

I want to anchor a button to the bottom center of the screen.

To set its position, I'm using:

System Every tick

   set X to windowWidth/2

   Set Y to WindowHeight-100-(spin_btn.Height/2)

The button has its origin set to the center.

The result is that the X & Y values vary widly with the screen size. E.g the longer the window, the more it disappears off below the window. The shorter the window, the more the object launches into outer space. Same with the X value. Its only actually correct when the window size happens to be the same a the window size set in the project.

Here is a 1 sprite capx file:

https://www.dropbox.com/s/gx2e1gnfn1t1uyy/middleAnchorProblem.capx

This is making life very hard...

Not a bug: WindowWidth and WindowHeight are not related to the viewport, so halving them does not give you the middle of the screen. Use the system viewport expressions instead, e.g. (ViewportLeft("Layer 0") + ViewportRight("Layer 0")) / 2 to get the X position of the middle of the screen.

Wow. That viewport stuff works, thanks. I need to draw some diagrams to get my head around it.