Wrong mouse position passed to VTK

[phcerdan]

It seems there is a wrong coefficient in the Y axis.
At the bottom of the viewer, the mouse position (from imgui)
and the mouse position in the vtkRenderWindow are the same.

But going upper in the Y axis, a gap develops. The vtk mouse position
is lower than the real mouse position.
I am not sure what happens, it's not a failure on "fixed" heights (like menu)
but some kind of coefficient.

[jspanchu]

The mouse event code looks normal. I wonder if this has something to do with window sizes..