QwtPlotGrid lines missing at start point

[Uwe]

And I'm using QGraphicsView not canvas...

As your problem is about the plot canvas - not sure what you are doing, but your response doesn't make any sense.

Anyway: here https://sourceforge.net/p/qwt/code/H...s/stylesheets/ you find a couple of sample stylesheets.
Plot items can't be styled using stylesheet as they are no widgets.

Uwe