@s_bach said in Communication between DescriptionTool and GeUserArea: The typical modern approaches are patterns like Model-View-Controller or Model-View-Presenter. In such models, you don't "send data around". Thanks for mentioning this. As stated in my opening post, this is what I have been using, where the "model" is a singleton class, available as a global variable to all plugins to synchronize and share data. Maybe not quite the exact wording. I was just wondering if there is another means of providing this "model" instead of using an instanced (singleton) class via a global variable? So in your example, the interaction with the DescriptionToolData would write data into the model. And the GeUserArea would read that data from the model. The example I provided isn't making use of a "model" as it already represented too much code just to point out the bug that slipped into R21. There I indeed used a very simplified solution by "sending data around". But an overall "thank you" for bringing up the model-view discussion, as this made me realize I could use an observer pattern in another project of mine which would fix its current poorly chosen design. Daniel

Thanks, @m_adam! That should put me a step closer.

@zipit Thank you. That'll help me.

@m_adam Thank you very much ! it is certainly helpful !!