Qt app UI elements randomly rendered as blank/black in Docker - c++

Question

I prepared Dockerfile to build Docker image of my Qt application. To run the application I use X - I enable access to X server (xhost +local:root), then I use the following command to run it:
docker run -it --env="DISPLAY" --env="QT_X11_NO_MITSHM=1" \
--volume="/tmp/.X11-unix:/tmp/.X11-unix:rw" mindforger:latest mindforger
The problem is that some Qt UI elements (menu items, dialogs, ...) are rendered blank in black (randomly) - check the screenshot below:
I'm on Ubuntu 16.04.5 with Docker 18.06 and Qt 5.01.

Answer 1

I had the same problem, and I couldn't solve it formally. But we found an alternative workaround to not display the error:
In our case, we have four QComboBoxes in a window. Our problem was that after starting the app, the second (sometimes the first) combo box you clicked displayed a black popup. So what we did was initializing the window with two dummy combo boxes, calling the showPopup method, and then hiding both the popups and the combo boxes. So the user can't notice the error. I hope you can make something similar with your app.

Answer 2

I had the same problem and found this solution which you have to run after starting the docker container. Once the specific docker container is started, run the following command within the docker container.
export QT_GRAPHICSSYSTEM="native"
Once this is pasted and executed within the docker terminal session, run the desired QT application and this black box problem should go away. You could even paste this option inside your docker's .bashrc if you didn't want to run it every time manually.

Answer 3

None of the posted solutions solved the identical problem that I encountered. However, this did fix it:
QT_GRAPHICSSYSTEM=raster

Answer 4

In my case (Qt5 application) I resolved this by adding the param --shm-size 128M, mounting /dev/shm:/dev/shm should work too.

Answer 5

I ran into this problem trying to get Google Earth Pro to work in Docker -- several dialog boxes and a few menus would be black-on-black or random pixels.
That specific graphics issue was solved by adding --ipc host to the create (or run) command.
Here is the distilled create command that I used; I didn't have to disable or configure shm (and none of the shm suggestions I tried helped):
docker create \
--ipc host \
-e DISPLAY -e XAUTHORITY \
-h "$HOSTNAME" \
-u "$(id -u):$(id -g)" \
--device /dev/dri/card0 \
-v /dev/dri/card0:/dev/dri/card0 \
-v /tmp/.X11-unix:/tmp/.X11-unix \
-v "$XAUTHORITY:$XAUTHORITY" \
my-qt-app
A small break-down:
--ipc host - This is what fixed the "black menus/dialogs"
-v "$XAUTHORITY:$XAUTHORITY", -v /tmp/.X11-unix:/tmp/.X11-unix and -e XAUTHORITY/-e DISPLAY is required or the app doesn't launch and complains about not finding a display server and complete failure without the -v $XAUTHORITY:XAUTHORITY
-v /dev/card0:/dev/card0 (in my script, I find those somewhat naively using findfind /dev/dri -maxdepth 1 -type c) is required to avoid Mesa errors, however, the application still works (poorly).
-u ... My implementation "hides" docker from the user, so it creates the container as the user, sets it up with a containerized "fake" version of their user account and uses it to launch the app, which the docker container is configured to use when it runs it. ...avoiding root GUI apps.