show fullscreen navigation after a short delay when activating at bottom, so it won't show when quickly touching the bottom
show fullscreen navigation after a short delay when activating at bottom, so it won't show when quickly touching the bottom

JackieXie168/skim,JackieXie168/skim,JackieXie168/skim,JackieXie168/skim,JackieXie168/skim