Python->JavaScript control mechanism

[uliska]

We will have to implement a (most generic) structure to control the SVG view from Python, e.g. the Object Editor. Some tasks:

• identify the currently selected element
• access that element
• pass values and parameters from Python to JavaScript
  (this can be through a number of substeps:
  • execute JavaScript code
  • this will call a slot in JSLink
  • this will return a value to be used by the JavaScript code

This has to be realized using signals and slots, and it has to be discussed which modules/tools/classes are responsible for which part.