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Twitter post by Daniel Feldman (@d_feldman): Linux is the only major operating system to support diagonal mode (credit [Twitter] @xssfox). Image shows an untrawide monitor rotated about 45 degrees, with a horizontal IDE window taking up a bottom triangle. A web browser and settings menu above it are organized creating a window shape almost like a stepped pyramid.
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Legitimate apps key off screen rotation do fancy stuff. Web pages let the browser render them and don't try to do fancy stuff. It's not that fucking hard.
Follow up question, would it ideally work like the old Java Applets then, where you have to explicitly ask to launch a web app?