Instead of overloading QwtPlotZoomer::zoom() better overload QwtLinearScaleEngine::divideScale() - this is the right place for your first code snippet !
The motivation behind the second seems to be to right/left align the min/max tick label, to avoid the extra space at the borders ?
Which of your code snippets doesn't work with Qwt 6.0 ?
Uwe
Bookmarks