A way to align different QwtPlot objects?

[agarny]

I have several QwtPlot objects, which are used to plot something against time. Now, the scale of that something can vary, meaning that the labels used to render the Y axis can be different from one QwtPlot object to another, and this results in the length of the X axis of my QwtPlot objects being different too. An example of what I am talking about can be seen here (https://cloud.githubusercontent.com/assets/602265/7787729/1240278a-0213-11e5-97a8-37f2e6eb76d1.png) (ignore the red "OV"; the screenshot was annotated by a colleague of mine).

That difference in length of the X axis of my different QwtPlot objects is clearly not neat. I was therefore wondering whether there would be a way to ensure that they are all of the same length?

Cheers, Alan.

[Uwe]

This has been asked and answered many times - check the forum and/or have a look at the plotmatrix example.

Uwe

[agarny]

I did check, but clearly not using the right keywords. Anyway, thanks for the tip, I am going to check the plotmatrix example.

[Alekon]

plotmatrix gives a useful.

But further problem is Y-axis (left or right) title. For long string with several words it can occupy >=1 lines, so the plots might be unaligned again. E.g. first plot has 1 line Y-axis title and second plot has 2 lines Y-axis.

How is it possible to disable wrapping of axis titles? Or, may be other way?

Thanks.

Added after 37 minutes:

Obviously, title font (size, family, etc.) also affects on title width. How is it possible to specify title width for QwtScaleWidget internal layout?

I think it will be amazing if a QwtPlot will have a feature for such alignment with other plot:

QList<QwtPlot*> layoutSyncingPlots(); // all syncing plots
void QwtPlot::addLayoutSyncingPlot(const QwtPlot& other);

In that 'layout syncing' group each plot tracks other plots and best syncing layout is found and applied for all plots in the group after any scale or size change. Of course, that syncing maybe better to implements through a dedicated separate class.

[Alekon]

11254
In the attach there are two plots with left-aligned X-axises (using "plotmatrix" example's way). How to align right axises? Note, that the plots differ by legend sizes and using/not using right Y-axis.

[Uwe]

You could try to align the legend by manipulating the sizeHints of the legend items ( maybe by overloading QwtLegend::createWidget() ). Another option is not to insert the legends into the plot layout ( QwtPlot::insertLegend() ) and to put it into a QGridLayout instead.

Uwe

[Alekon]

Thanks a lot. Solved the problem by suitable for my requirements way. Legend was aligned with sizeHint() overriding; scales were aligned with adding fake invisible right Y-axis to the plot that has no right Y-axis. Now, it looks like this (attach). If someone interest the solution I can share the details.
11257

[Alekon]

I have encountered a problem. Under some size the legend does not placed in right side, there is a gap appears (see attach). The plot is brushed as follows:
qwtpltMain_->setAutoFillBackground(true);
qwtpltMain_->setBackgroundRole(QPalette::Dark);
11258

[Alekon]

Hello Uwe,

I'm using Qwt 6.1.0. Please look QwtPlotLayout::layoutLegend() (line 775) and QwtPlotLayout::LayoutData::init() (line 85) routings. It seems that there is twice compensation of legend width (vertical legends are considered) by value "legend.hScrollExtent". Is it right?

Thanks

... as an option to explore the problem quickly I patched QwtLegend::scrollExtent() to permanently return 0 regardless of a scrollbar need, so twice compensation becomes "masked". It works as I expected - no extra width increasing. So, there is the twice compensation bug.

[Alekon]

I have another issue (see attach). X-axis label (8000) on bottom plot shifts the plot canvas, so there is extra space between canves and legend. How can I "trim" scale widget to be under plot canvas without extents?

Thanks.
11260

[Uwe]

It seems that there is twice compensation of legend width (vertical legends are considered) by value "legend.hScrollExtent". Is it right?
Yes, I have added a bug report: https://sourceforge.net/p/qwt/bugs/241/

Uwe

Added after 4 minutes:


I have another issue (see attach). X-axis label (8000) on bottom plot shifts the plot canvas, so there is extra space between canves and legend. How can I "trim" scale widget to be under plot canvas without extents?
The default setting is like this - your code seems to change it by setting QwtPlotLayout::setAlignCanvasToScale().

Uwe