Convert event.globalPos() to world coordinates

[Seboon]

Hi Alexey and others,
I'm trying to make a script using a Qrubberband on Orthoview in order to select area on orthomosaic.
I'm able to draw the rubberband and create rectangular shape from it.
The problem is that it doesn't fit the rubberband area.
I think the issue comes from reprojecting the event.globalPos() to world coordinates.
so my question : how to reproject mouseclick coordinates to  world coordinates, as it's done when moving mouse and coordinates shown in the Label  bottom right off the screen??

See my code and cap for more details.

Thanks a lot,

Sébastien