Is it possible to get a legend ID using QwtLegend?

Hello,

I'm using QwtLegend to insert legends in my plot area, I setted my legend as CheckableItem and I added a connection:

Code:

---

connect(plot.at(iPlotCounter), SIGNAL(legendChecked(QwtPlotItem *, bool)),this,
	SLOT(setConfig(QwtPlotItem *, bool)));

---

Normally my plot has 8 curves and there is a possibility that two curves have the same legend name (the same title). I know it's possible to get the name when I click on one legend:

Code:

---

void MainWindow::setConfig(QwtPlotItem * te, bool ta)
{
	if (ta==true)
	{
		qDebug() << te->title().text() << "\n";
		qDebug() << te-> << "\n";
	}
}

---

But because of the problem that I can have two legends with the same name, get the name doesn't help me so much. So, I was wondering if there is a possibility to get an ID, for example, when I add each legend, maybe there is a value for each, in my case 8, maybe an ID that comes from 0 to 7, I don't know.

Anyone knows if is there an ID, a specific number for each legend or the only possibility is using the name?

Thanks in advance
Best Regards

Try using z-order (QwtPlotItem::z()).
If it won't work out-of-a-box try setting z-order when creating the curve and then retreiving it later.
It's not foolproof as anything can change it but always something.

Hi,

I didn't work for what I want. I was trying to do this:

Code:

---

void MainWindow::setConfig(QwtPlotItem * te, bool ta)
{
	if (ta==true)
	{	
		QList<QWidget*> t = plot.at(iPlotCounter)->legend()->legendItems();
		for (int i=0; i<t.size(); i++)
		{
			qDebug() << "Name: " << ((QwtLegendItem *)t[i])->text().text() << "\n";
			qDebug() << "Checked: " << ((QwtLegendItem *)t[i])->isChecked() << "\n";
		}
        }
}

---

The problem is: when I use QList, I don't know why (maybe you can explain me), my list gets unsorted, for example, my legend's names are:

Current
Voltage
Voltage
Charge
Discharge
Total

I was expecting that my list order would be the same and then I could use the index as my index, but when I get the list, it's always in a different order.

After this problem I was trying to find any information that I could use, inside of this legendItems that I got, I found a variable that calls "ser_no", I don't know how to take the value of this variable, but it seems to be what I need, because the values are increasing according by the plotted order, then I could use them as my index.

Ok, I have three other questions:
First: Is it possible to create a QList using (QList<QWidget*> t = plot.at(iPlotCounter)->legend()->legendItems();) and make sure that the list has the same order that's been showed?
Second: Why does QList change the order?
Third: Anyone knows how to get this "ser_no" or what this "ser_no" means?

Thanks in advance
Best Regards

Hey,

The legend item list is sorted, but the key is not the text but the pointer to the widget:

Code:

---

"Curve 5" QwtLegendItem(0x931ead0) 
"Curve 0" QwtLegendItem(0x931eb48) 
"Curve 4" QwtLegendItem(0x931ebe8) 
"Curve 1" QwtLegendItem(0x931ec10) 
"Curve 6" QwtLegendItem(0x931ecb0) 
"Curve 3" QwtLegendItem(0x931ef08) 
"Curve 2" QwtLegendItem(0x933ad50) 
"Curve 7" QwtLegendItem(0x933ae90) 
"Curve 8" QwtLegendItem(0x933af30) 
"Curve 9" QwtLegendItem(0x933afd0)

---

So answer to question 2 is: list doesn't change the order, it's just ordered by something else that you'd expect.

I don't know where you got the 'ser_no', but I couldn't find it anywhere in qwt 6.0.1 source I have.

To answer your original question:
Create additional map of your curves in format: QMap< QwtPlotItem*, int >, where pointer is your curve, and int is its ID (may be index in other list you have or anything else that you find useful);
this way in your setConfig() you can get ID of each curve from the pointer you're getting there.

Now I have a question:
Why do you need it for?
There may be something wrong with your thinking here.

Hello,

I found a way to get the ser_no.

Code:

---

((QwtLegendItem*)legendList[i])->identifier().serialNumber();

---

It's working know, I have the ID I need and I can find which legend even if they have the same name.

Thanks for your help.
Bye

I'm sorry to reopen this topic.

I have the same problem but QwtLegendItem doesn't exist now with Qwt 6.1.2! Now we only have QwtPlotLegendItem.

This line is not possible :

Code:

---

((QwtLegendItem*)legendList[i])->identifier().serialNumber();

---

I just can do this but it's not ok :

Code:

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QwtPlotItem *plotItem = plot_spectre->infoToItem( itemInfo );  
    nom_courbe = plotItem->title().text();

---

What can i do?

Maybe put the legend with QwtPlotLegendItem but i don't arrive to put on right the legend as :

Code:

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insertLegend(legend, QwtPlot::RightLegend);

---

The legend is inside the plot.