qwt overlay plot

[Surfman19]

Hi,

i have a plot in qwt. i would like to add some overlay to show that a curve is violated from point t to t+x.

Is there a way to achieve this feature?
e.g.
https://community.dynatrace.com/comm...4014427&api=v2

Thanks,

[Uwe]

Your link doesn't work for me.

Uwe

[Surfman19]

hm....

i also upload an image, can you see it now? i refer to the red rectangle overlay indicating a violation in the graph... Screen Shot 2015-06-14 at 3.07.15 PM.jpg

[Uwe]

Well this looks simply like filling some area with a red pen and a semitransparent red brush ( guess with an alpha about 100 ).
Candidates for the implementation are QwtPlotShapeItem or QwtPlotZoneItem.

Uwe

[Surfman19]

thanks for the info.
i have a problem with qwtplotshapeitem: it does not overlay with the plot, any idea?

how can i set the coordinate of the rectangle to the ymax, ymin and to the plot item x=10 till x = 100?

QColor color(255,0,0,100);
 
		QPainterPath path;
		path.addRect(20, 20, 60, 60);
 
		QwtPlotShapeItem *pitem = new QwtPlotShapeItem();
		pitem->setItemAttribute(QwtPlotItem::Legend, true);
		pitem->setRenderHint(QwtPlotItem::RenderAntialiased, true);
		pitem->setShape(path);
		pitem->setPen(color);
		pitem->setBrush(color);
		pitem->attach(plot.get());
 
		plot->replot();

QColor color(255,0,0,100);

		QPainterPath path;
		path.addRect(20, 20, 60, 60);
		
		QwtPlotShapeItem *pitem = new QwtPlotShapeItem();
		pitem->setItemAttribute(QwtPlotItem::Legend, true);
		pitem->setRenderHint(QwtPlotItem::RenderAntialiased, true);
		pitem->setShape(path);
		pitem->setPen(color);
		pitem->setBrush(color);
		pitem->attach(plot.get());
	
		plot->replot();

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[Uwe]

i have a problem that the qwtplotshapeitem does not overlay with the plot, any idea?

Probably - if I would know, what is meant by "does not overlay".

how can i set the coordinate of the rectangle to the ymax, ymin and to the plot item x=10 till x = 100?

If ymin/ymax simply mean top/bottom of the plot canvas, than your looking for QwtPlotZoneItem.

Uwe

[Surfman19]

i mean that the qwtplotshapeitem should be on top of my QwtPlotCurve, at the moment the qwtplotshapeitem moves the QwtPlotCurve to the bottom...
see here:
http://img.ctrlv.in/img/15/06/14/557dd35c189d0.jpg

how can i extract the x coords from my QwtPlotCurve and pass it to qwtplotshapeitem? from x=10 to x=100
ymax = top, ymin = bottom of the qwtplot.

edit: i solved the problem.... just used wrong coords for QPaintPath, addRect.... i only need to specific the region of the violation with the coordinates of .addRect...

how should the QwtPlotZoneItem be useful here? can you show an example?

does qwt use opengl in the behind the scenes per default? could you use it? do people use it to render the plot?

[Uwe]

i mean that the qwtplotshapeitem should be on top of my QwtPlotCurve, at the moment the qwtplotshapeitem moves the QwtPlotCurve to the bottom...

It doesn't - your rectangle simply doesn't match the y coordinates of your curve ( those are much smaller ) and in its default settings it has an effect on the autoscaler.

how can i extract the x coords from my QwtPlotCurve and pass it to qwtplotshapeitem? from x=10 to x=100
ymax = top, ymin = bottom of the qwtplot.

QwtPlotCurve inherits the API of QwtSeriesStore<QPointF>.

Uwe

[Surfman19]

ok, will look into it.

how can i detach the qwtplotshapeitem after i dont need it any more? i dont want to delete the object, bc i activate the qwtplotshapeitem again later...

[Cah]

i dont want to delete the object, bc i activate the qwtplotshapeitem again later

Have a look at
QwtPlotDict::detachItems(...)