I am new to programming, and have finished programming my experiment using Mac pro Catalina. The stimuli were presented nicely in the centre of the screen as I want but in other computers (Mac/Windows) they appear in the lower right corner of the screen. So there might be an issue with reading the size of the screen someone is using or it could be of another issue not really sure!
If anyone could help?
Normally when you open a screen, you get back the window rect ([win,winRect] = PsychImaging('OpenWindow', thisScreen)), the size of the window whre winRect(3) is the width and winRect(4) is the height. You can then use that to “normalise” your stimuli. I always normalise to use visual degrees from the display center as that makes most sense for most visual experiments. E.g. +4 degrees in X position is xpixels = (width/2) + (4 * pixelsPerDegree), xpixels is what I pass to PTB.
Beware however macOS systems or systems with hiDPI displays, as there may be OS bugs in drawing that can occur. For example, on my iMac by default it opens a display at the “virtual” resolution, but displays at the actual resolution so I only see 1/4 of the image (I think the bottom left like you mention). If I just used pixel coordinates to make it look OK there, then it would be wrong everywhere else… You need to check what winRect claims vs. what you macOS physical screen size is…
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