Screen size not working?

Hi, I’m trying to create a grid that have the 90% width and 80% height of the screen.

I tried all function but no one give me the correct pixels of the screen, all are returning the same value (the size of the canvas). I don’t care the size of the canvas. All i need this the screen size to create my grid.

Did you set it in the properties dialog?

Did you mean in canvas?

image

I tried with checkbox selected and unselected. not working as well…

I can bring you more code if you need.

Thank you!