QwtPlotZoomer: cut of markers close to canvas borders

[corrado1972]

Hello you all, I'm usign QT 4.7 and QWT 6.0.0 RC5

In a previous post I looked for suggests to implement a railway flow, and thanks to your advices I made the work.
At the present I'm in trouble with the use of QwtPlotZoomer. I'm using it to control automatically the zoom with mouse facilities patterns.
When the user zoom in and zoom out into the zoom stack, no problem.
When the user choose the maximum zoom out the curves are plotted too close the border of the canvas, cutting off some markers. Please see the comparison shots attached.

How can I fix this issue ? I would that zoom doesn't cut off the labels of the qwtplotmarkers.