Scale and grid unsynchronized

[Ernst K. <ern...@tu...>]

Hallo,

I am using qwt for scientific graphs and I need a lot of zooming operations
and panning. If you are moving (or zooming), however, under certain
conditions the scale and the grid/curves in x-direction use different
coordinate systems. This means that curves/grid and scale ticks are drawn on
different positions. You can reproduce this effect very easily in the
event_filter example. Move the scroll bar very slowly pixel by pixel and
look at grid/scale ticks: whenever a major tick label disappears, grid and
scale ticks are unsynchronized after the first replot. If you move the
scroll bar to the left, the grid is shifted to the left (compared to the
ticks) and vice versa. You see this effect very clearly if the -20 tick
disappears/appears. It looks like the transformation factor is calculated
wrongly if a tick label disappears/appears because the right of the diagram
remains synchronized in any case.

Can somebody help on this problem? In my application it is rather
problematic if scale ticks and grid are drawn differently.

Ernst Kozeschnik
Graz UT