The API to get channel values only returns values if the channels have been set from Simple Desk.
If a channel is not set by Simple desk (e.g. a set by a widget) then the channel values are '0' in the API response.
Is this a bug?
You are right, the description at http://qlcplus.org/Test_Web_API.html is wrong. It indeed returns values from simple desk.
The function's intent is to help in implement Simple Desk in web interface.
TODO:
@massimo: adjust description of the Web API page
anybody: add another function to retrieve channel values
Fixed on GIT
However, I realized it still has issues with relative values coming from EFX.
The "native" simple desk works properly as it is a DMX source, but the web interface gets preGM values without the relative values added