Distortion while moving objects in Portrait mode

Question

I am currently working on a Kiosk system based on the Raspberry Pi 2 running Raspbian which runs a Java app. Everything works perfectly well, except for a distortion on the screen which appears while objects are moving. Normally, this wouldn’t be a problem, but I have a list on the Java app which will be extensively used by the users. The distortion is visible while scrolling on this list. The following image shows how this distortion looks like:

The link below shows this in action:

A GIF showing the distortion

What I know so far:

• This only occurs while the screen is rotated in portrait. I have rotated the screen by 270* by setting “display_rotate=3” in /boot/config.txt. It also appears when the screen is rotated by 90* by setting “display_rotate=1”
• It is not dependent on the screen resolution or the “hdmi_group"
• This doesn’t happen only on the GUI, the distortion is also visible during boot time
• Overlocking doesn’t affect the distortion
• It always appears on the right-bottom side of the screen
• This issue was also present in Ubuntu Mate

Answer 1

You could try the rotation using X instead of setting it in config.txt. I don't promise it will fix your issue, but it seems to work fine here for me (I did not compare it to the config.txt method, however). I believe these are two pretty distinct mechanisms.

The Xorg server on the Pi uses a generic framebuffer driver, fbdev. Note that this was not written specifically for it and should be available in any GNU/Linux ARM distro.¹

A limitation of that driver is that it cannot do a dynamic rotation; normally something like xrandr --output default --rotate left could be used to rotate the screen with the server running, but this will fail on the Pi because the fbdev driver can't do that.

However, you can configure a static rotation. I created the following as /etc/X11/conf.d/rpi.conf (this directory does not exist by default on Raspbian, but you can create it, and the file, as root):

Section "Device"
        Identifier "RpiFB"
        Driver "fbdev"
        Option "rotate" "CCW"  # As in, counter clockwise
EndSection

Section "Monitor"
        Identifier "generic"
EndSection

Section "Screen"
        Identifier "screen1"
        Device "RpiFB"
        Monitor "generic"
EndSection

Section "ServerLayout"
        Identifier "slayo1"
        Screen "screen1"
EndSection

This is pretty minimal and derived from a hint here and my reading of man xorg.conf. You don't have to use it exactly as is, the key part is the Option "rotate" line in Section "Device". The possibilities are:

• "CCW", Counter clockwise aka. left
• "CW", Clockwise, aka. right
• "UD", Upside down.

If it does not work, shut X down and have a look at /var/log/Xorg.0/log. If you left the Identifiers the same there should be a bit in there like:

[158797.529] (==) ServerLayout "slayo1"
[158797.529] (**) |-->Screen "screen1" (0)
[158797.529] (**) |   |-->Monitor "generic"
[158797.532] (**) |   |-->Device "RpiFB"

Somewhere after Using config directory: "/etc/X11/xorg.conf.d". If that's not there, the problem is your configuration wasn't read (but there's no reason it shouldn't be on a stock system, see man xorg.conf again). If it is, keep reading down the log -- Xorg should report your typos/errors.

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^{1. The driver does identify the hardware (BCM2708 FB (video memory: 600kB), or 4050kB on the Pi 2) but it will do this on, e.g., a general purpose Fedora ARM distro that includes no pi specific software. I'm mentioning this to make it clear there is nothing special about the Raspbian Xorg driver and any documentation you find around for the fbdev driver, pi oriented or not, should be applicable; witness "the hint" I found about the rotate option was from a blog about DisplayLink devices.}