Blue line following my touch on the screen of Huawei devices Sometimes strange 'worm' and 'dust cloud' starts to follow my finger when browsing with my Huawei Honor 7.



When the finger is not touching the screen anymore, the line disappears.
I can also draw over the navigation buttons at the bottom of the screen.
What is going on here?
It is Huawei's Knuckle Gestures.
From Use Your Phone with Your Knuckles,

Knock the screen with a knuckle and hold it until a blue dot appears. You can then drag your knuckle [...]. As you move your knuckle, a blue line will appear on the screen [...].