When I placed one of my phone on top of the Nexus 7 tablet, the camera of the phone can generate touch events when it touch the tablet screen. It happened to be that on the tablet, it is on the Developer options screen, and the camera of the phone turned on option of "Pointer location" and "Show surface updates". The coordinates and other values of the touching point would be displayed at the top of the screen near the row of notification bar, and the motion event trace would be drawn on the screen, the values are dX dY, (or X, Y when the touching point is moving), Xv, Yv, Prs, Size, the values of Xv and Yv look like to be speed or velocity, Size is the value of area value of the touching point, not sure the meaning of Prs, is it pressure or the perimeter value?
If "Show surface updates" is turned on, the screen would flash with different color.
The problems is if I turned on "Show surface updates" and clicked on the Home soft key, the home screen will keep blinking , indicating there are some surface updating events happening, though I did not touch the screen surface. I checked this on my phone, there is not such problem.
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