Gazebo recognize collision and show in rqt

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In Gazebo it is possible to actvate self-collision for all links. Now the links can't move through other links. Thats great. I created an rqt-User-Interface to control all joints of my robot (mobile platform + mounted ur-10 robotic arm). Now i want to get a message in my rqt interface which says: "Hey, there a collision with link1 and link2 at x y z of link1 ..." Whats the most common way to detect collisions in Gazebo and send a "collision"-message to any topic? Is there any rqt-plugin to visualize that or do i have to create my own plugin for that?

Best regard and thanks for your support. Max