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Hello, experts. My environment is Ubuntu 18, ROS2 Crystal.

I installed the rqt-graph plugin to debugging. But, I can't find out the plugin on rqt-gui. In normal case, It should to be on "Plugins->introspection->Node Graph".

After $ rqt ---force-discover, it is working now. Further, other plugins come out on "Plugins" tap.

What is the "rqt --force-discover" option meaning?

The description, written on the rqt usage guide, said below.

"--force-discover force a rediscover of plugins"

Do you explain "rediscover" progress meaning?

Originally posted by harderthan on ROS Answers with karma: 98 on 2019-11-21

Post score: 0

Original comments

Comment by stevemacenski on 2019-11-21:
Please remember to only ask the question once


1 Answer 1


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The list of available plugins is cached for one day (https://github.com/ros-visualization/qt_gui_core/blob/bccb8a2066116f105a9765146576bdedaf174263/qt_gui/src/qt_gui/plugin_manager.py#L61) to speed up repeated invocation of rqt. If plugins are added within that period they don't show up automatically since the cached information is used.

Passing --force-discover will invalidate the existing cache and ensures that the list of available is queried again (which takes a little bit of time, depending on the size of the ROS installation up to a few seconds).

Originally posted by Dirk Thomas with karma: 16276 on 2019-11-22

This answer was ACCEPTED on the original site

Post score: 1


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