It is not my intention to bump this topic every other day, but I just want to know if a response from devs is still in the pipeline.
So far, it seems that with R21 the obtained mouse coordinates are valid as long as the mouse pointer is hovering over the main Cinema application window. Once outside of that window the obtained coordinates are that of the last position inside the window.
This means that when the application is not full screen, or when multiple monitors are involved the coordinates outside of the window are useless. Most important is that one cannot find out if the mouse cursor is inside or outside the window and thus decide (or know) the obtained values are useless.
This isn't an issue with R20.
On the other hand, as far as I have understood with the release of S22, there will be no further service packs for R21. Which means any fix to this issue (if provided) will be S22 or R22.
Which brings me to the inevitable decision that I will need to ditch any further development for R21. There just are too many unresolved open issues for any of my current (and work-in-progress) plugins.