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There should be autohide option for video controller (would show up again when mouse moves over video area). Could have a "pin" icon at its top-right to keep it (by default) showing
Maybe the fullscreen action should unpin that automatically or have another unpin button when in fullscreen mode (?), shown as a pin inside brackets [...] or something. That pin would be unpinned by default
Question is whether this setting should be rememered (and if it should be remembered by-app only or by-activity too [could have option in export/pack activity dialog])