I observed one little issue, that mouse axes disappeared when we are zoomed in. So on my code walkthrough I saw that the QGraphicsColorizeEffect significantly lowers the performance of QGraphicsView, in short the whole eCAD.
And when I removed that effect the performance shoot up as well as the axes appeared.
So this color of axes must be set in some different manner and for now this issue has been resolved.
Now i’m working on Snap-to-Grid feature that eCAD lacks.