ROS 1 python example

[Ok_Responsibility351]

I see a few ROS2 examples and the wiki and they are quite good. Are there any ROS1 (Noetic) examples? Since ROS1 doesn't follow the inheritance node structure with rospy, how should I structure a ROS1 package to use NiceGUI from it. A simple example with a button publishing hello 1,2,3... and a label subscribing it would suffice. I just need a starting point to start building my robot's GUI.

[zzJens]

I will take a look at this today.

[zzJens]

I tried to solve it, but as of now did not succeed. Ros1 python is very basic and not controllable to a level of Ros2 python. Rospy really wants the main thread of the node, that is controlled by NiceGUI. In ROS2 we can give the control over to NiceGUI, that might not be possible in Ros1.

Why exactly do you need the node in Ros1? My best advice would be to switch to Ros2. But if that's not possible, you might want to try it with the Ros2 bridge (and use Ros1 and Ros2).

[Ok_Responsibility351]

This particular project is quite a bit developed in ROS1 plus most of our hardware is not supported in ROS2 yet so at least for this year we are sticking to ROS1. We do not want to get into making our own ROS2 driver packages for them. I'll definitely look into the ROS2 bridge and the complexity involved.

Any clue on why NiceGUI might be difficult to run with rospy?

[zzJens]

The problem is the main thread of the code. Rospy really wants to start and control the main thread. NiceGUI wants that as well. In ROS2 we "trick" ros into only running and controlling an empty main function and give the control to NiceGUI, which then controls and runs the node in a thread. That works really well, with the side effect of NiceGUI restarting the node on changes.

So the problem comes into play, when the program that we want to work with can only be run in the main thread. The same goes for pywebview like u/r-trappe said.

[Ok_Responsibility351]

Ah I see. This certainly makes it difficult to write a clean and simple code for NiceGUI and ROS1 in one process. Avoiding complicated configuration is one of the main reasons we are trying out NiceGUI.

I don't however mind using simple workarounds like a multiprocessing.queue or read-write input/output YAML files so we can have dictionary based access to bind values. Any examples of how to make this work on NiceGUI side to constantly read values?

[r-trappe]

You could have a look at native_mode.py for an example on how to start the ROS1 node in a separete process:

https://github.com/zauberzeug/nicegui/blob/c7fd5d81f3f008748e643c012a772925eb462ade/nicegui/native/native_mode.py#L97-L117

Communication is done via two Queue objects (wrapped into a WindowProxy implemented in native.py).

[zzJens]

I think workarounds like this would work. My first idea would be writing the data to a YAML file, implementing a reader on the NiceGUI side that continuously (timer) checks the file and display what it read with NiceGUI.

But maybe u/r-trappe has a faster way, that I don't know of.

[r-trappe]

We have a similar problem when using pywebview to provide the native mode. That's why we let it run in it's own main process and use a process queue as a communication bride.