How to align QwtScaleWidget with QwtPlot

[mirrorrorrim]

I create a QGridlayout and place a QwtPlot in the center and four QwtScaleWidget at the side of Top, Bottom, Left, Right of the QwtPlot.
And all the scales of QwtPlot itself are disabled by enableAxis( ..., false ).
I initialized the four scales like below:
scaleTop -> setScaleDiv( plot -> axisScaleDiv( QwtPlot::xTop ) );
...

But it is found that the four scales are not matched with the plot.
The value range of the scales is ok, but the ticks are not aligned with the grid of the plot.
How could i do something to fix this?Thanks…

If this is done, I will place several plots in grid and a lots of scales around all the plots.

Just like below:

blank scale scale
scale plot plot
scale plot plot
blank scale scale

[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.