How to align QwtScaleWidget with QwtPlot

[d_stranz]

Your problem is probably that you are not setting the margins and / or the spacing in the grid layout to 0. All layouts automatically insert some extra space around the widgets inside them. In most cases, this leads to a pleasing layout. In this case, it leads to misalignment of the scales and plot. See QLayout::spacing(), QLayout::setContentsMargin(), QGridLayout::setHorizontalSpacing(), and QGridLayout::setVerticalSpacing().

You will have to play around with it. If you want to have your 4 plot instances separated from each other (i.e. non-zero spacing between some, but not all widgets in the grid), you might have to embed layouts within layouts (for example, three vertical layouts inside a horizontal layout) instead of a single grid layout.

[mirrorrorrim]

Your problem is probably that you are not setting the margins and / or the spacing in the grid layout to 0. All layouts automatically insert some extra space around the widgets inside them. In most cases, this leads to a pleasing layout. In this case, it leads to misalignment of the scales and plot. See QLayout::spacing(), QLayout::setContentsMargin(), QGridLayout::setHorizontalSpacing(), and QGridLayout::setVerticalSpacing().

You will have to play around with it. If you want to have your 4 plot instances separated from each other (i.e. non-zero spacing between some, but not all widgets in the grid), you might have to embed layouts within layouts (for example, three vertical layouts inside a horizontal layout) instead of a single grid layout.

I've set both the margins and spacing to be 0. But it still does not fix that.

I noticed that all the scales of the plot itself which are enabled by enableAxis() do start from the point what has a small distance to the border. Cause I need them to be displayed as metioned, I have to disable all the scales provided by QwtPlot itself and new() them and place them in a grid layout and so I encounter this problem.

It seems using QwtScaleWidget::setBorderDist( startDist, endDist ) may work on this situation. But I don't know how to give a suitable value for startDist. Or, shall I use scaleTop -> setScaleDiv( plot -> axisScaleDiv(...) ) to make the scales have the same value range of the plot? There is another way to initialize all the scales?

d_stranz, thank you very much and wish you success in your work.
This problem has perplexed me two weeks. Someone gives me a hand?
Uwe...?

[mirrorrorrim]

Uwe, can you help me?If there is a way I have not found or what else?
If qwt can not support this, I have to give up and find another way to implement my application instead of qwt lib.

[Uwe]

You need to synchronize the coordinate system of the plot to the coordinate systems of your external scales - what means that the scale maps ( QwtScaleMap ) used for rendering the plot items have to be the same as those you are using for your external scale widgets.

In your case I guess that the widget coordinates need to be adjusted ( translation between different widget coordinates ). f.e. by overloading QwtPlot::canvasMap().

But I don't have enough information about your situation to tell you in detail what to do.

Uwe

PS: I will be offline the next days

[mirrorrorrim]

Uwe,
thank you so much and I'll try what you told me.
Have good days.

[mirrorrorrim]

Uwe
I failed, so I decided to try another way based on Qt.
Maybe I misunderstood your meanings.
Thank you any way.