RViz2 can't load svg files.

[xkaraman]

I was messing around with docker versions of ROS2 when i stumbled on a weird issue. The issue is that multiple warnings appear when launching RViz about loading svg files.

Using fresh docker containers:
docker run -it --gpus all --net host --ipc host -e DISPLAY=$DISPLAY -v $HOME/.Xauthority:/root/.Xauthority:ro ros:version
--ipc host is required for Qt to display the main vis panel correctly instead of all black. (at least in my system)

==

ros:humble

apt update
apt install ros-humble-rviz2
source /opt/ros/humble/setup.bash
rviz2

This loads RViz default svgs correctly.

==

ros:humble-perception

apt update
apt install ros-humble-rviz2
source /opt/ros/humble/setup.bash
rviz2

# apt install libqt5svg5 # this solves the warnings

This failes to load RViz default svgs correctly.
Multiple [ERROR] [1685452528.367825331] [rviz2]: Could not load pixmap package://rviz_common/icons/move_z.svg -- using default cursor instead. errors appear.

==

When installing rviz2, since there is no runtime-dependency on libqt5svg5, it doesn't get installed and therefore, fails to load the default svgs files required.

You might think this can't be right since humble-perception extends humble. The dockerfile of ros:humble-perception installs the necessary packages but doesn't install the recommended ones. libqt5svg5 gets installed with perception_pcl package as a recommended one, hence it is omitted for installation and somehow when installing rviz2 in humble-perception it is not recommended at all while in humble it is.

[clalancette]

I think the difference here is likely that in the ros:humble case, the apt install ros-humble-rviz2 command did the install (which implicitly install recommends), while in the ros:humble-perception case it was already installed by the Dockerfile (which uses --no-install-recommends).

The real fix here is that we should have an explicit dependency on the svg library somewhere in rviz2 or one of its dependencies (probably whichever component is responsible for loading).

[xkaraman]

I think the difference here is likely that in the ros:humble case, the apt install ros-humble-rviz2 command did the install (which implicitly install recommends), while in the ros:humble-perception case it was already installed by the Dockerfile (which uses --no-install-recommends).

Yeap, that is exactly the case of how it is not installed on humble-perception with a minor detail. RViz2 is not installed by default in humble-perception but some of its dependencies are and hence the svg library never gets installed since it is a recommended one for perception_pcl package. So when instructing apt install ros-humble-rviz2 even though we command to install both dependencies and recommended ones, since it's not a recommended package for rviz2 (how do you declare recommended in ROS packages?) it does not get installed.

The real fix here is that we should have an explicit dependency on the svg library somewhere in rviz2 or one of its dependencies (probably whichever component is responsible for loading).

Adding a dependency even though is not strictly one, as it still functions correctly without it minus the correct icons, seems a good idea.
I believe the error is coming from rviz_common at this function