I want to write a custom visual in ECMAScript (aka: JavaScript) that: displays HTML controls; passes the user input from those controls into a REST service; displays the output from the REST services...
I just noticed there is an option in the Desktop Client to GetData from a BlankQuery. It seems you can specify the BlankQuery as the data source and then hit Close and Apply and then you can work on your custom visual without having to have a data source. That might be one way to easily create custom visuals without having to go through Power BI to get the data. I still think obtaining user's input might be tricky going this way, but at least I can maybe create a custom visual now without having to define a data source.
