[Tor hat] It's not hard to extrapolate with a high degree of certainty, what your real screen size is if you are fullscreen (F11), so the same would apply with LBing fullScreenElement. That's at 100% zoom and ideally the system scaling at something common - it's not always that easy. LB makes it harder by masking the real value. The question is do we want to do this to fullScreenElement? It's behind a user action (and sites that did it without being transparent would scare users away). Do we want users in a fullscreen video that is already letterboxed due to aspect ratio, then be letterboxed again? Could we exempt video only? Would video then leak? Sometimes it's better to educate and allow functionality and usability for end users, who are required in large numbers to create your "crowd".
Bug 1450401 Comment 13 Edit History
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[Tor hat] It's not hard to extrapolate with a high degree of certainty, what your real screen size is if you are fullscreen (F11), so the same would apply with LBing fullScreenElement. That's at 100% zoom and ideally the system scaling at something common - it's not always that easy. LB makes it harder by masking the real value. The question is do we want to do this to fullScreenElement? It's behind a user action (and sites that did it without being transparent would scare users away). Do we want users in a fullscreen video that is already letterboxed due to aspect ratio, then be letterboxed again? Could we exempt video only? Would video then leak? Sometimes it's better to educate and allow functionality and usability for end users, who are required in large numbers to create your "crowd". edit: we could put fullScreenElement behind a prompt similar to fullscreen (F11) without LBing in tor browser - the prompt is to educate/warn but can also be disabled so as to not annoy the user