Change colour of specific item in Qwt Plot

[AhmedAlshawi]

Hi All,

I have developed a qwt that contains multiple QwtPlotShapeItems.

//Run a function to get an array of polygons
QVector<QPolygonF> polygonArray;
createPolygonArray(lines, polygonArray, maxdistance);
 
//add each polygon in the polygon array to the qwt plot
for (int j = 0; j < polygonArray.size(); j = j + 1)
{
    QwtPlotShapeItem *shape = new QwtPlotShapeItem;
    shape->setPen(QColor(0,0,0), Qt::SolidLine);
    shape->setTitle("shapeNumber_" + QString::number(j));
    shape->setBrush(QColor(130,130,130,50));
    shape->setPolygon(polygonArray[j]);
    shape->attach(&myPlot);
    V.push_back(shape);
}
myPlot.replot();

//Run a function to get an array of polygons
QVector<QPolygonF> polygonArray;
createPolygonArray(lines, polygonArray, maxdistance);

//add each polygon in the polygon array to the qwt plot
for (int j = 0; j < polygonArray.size(); j = j + 1)
{
    QwtPlotShapeItem *shape = new QwtPlotShapeItem;
    shape->setPen(QColor(0,0,0), Qt::SolidLine);
    shape->setTitle("shapeNumber_" + QString::number(j));
    shape->setBrush(QColor(130,130,130,50));
    shape->setPolygon(polygonArray[j]);
    shape->attach(&myPlot);
    V.push_back(shape);
}
myPlot.replot();

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I want to return to my plot at a later point in my code and loop through all the attached QwtPlotShapeItems, and if it's title matches what I looking for, then I want to change the colour of that shape. So for example:

//.....later on in my code, in another function that the plot is passed into (by ref)
for (int j = 0; j < myPlot.numberOfAttachedShapeItems(); j = j + 1)
{
    if (myPlot.attachedShapeItem[j].Title() == "shapeNumber_7")
    {
        myPlot.attachedShapeItem[j].setBrush(QColor(0,0,0,255));
    }
}

//.....later on in my code, in another function that the plot is passed into (by ref)
for (int j = 0; j < myPlot.numberOfAttachedShapeItems(); j = j + 1)
{
    if (myPlot.attachedShapeItem[j].Title() == "shapeNumber_7")
    {
        myPlot.attachedShapeItem[j].setBrush(QColor(0,0,0,255));
    }
}

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Is this possible, or do I have to recreate my plot each time I want to change the color of a single shapeItem?

Thank you!

[Uwe]

Is this possible, or do I have to recreate my plot each time I want to change the color of a single shapeItem?

Changing the brush only is fine.

Uwe

[AhmedAlshawi]

Changing the brush only is fine.

Uwe

I cant find how to change the fill colour of the plotitem. Could you see what I missing? Thank you for your help!

QwtPlotItemList plotItemList = myPlot.itemList();
for (int m = 0; m < plotItemList.size(); m = m + 1)
{
    if(plotItemList[m]->title().text() == QString::fromStdString(desiredName[i]))
    {
        plotItemList[m]-> //??? there is no setBrush to use here....I would expect to write...setBrush(QColor(0,0,0,255));
    }
    else
    {
        plotItemList[m]-> //??? there is no setBrush to use here....I would expect to write...setBrush(QColor(130,130,130,50));
    }
}

QwtPlotItemList plotItemList = myPlot.itemList();
for (int m = 0; m < plotItemList.size(); m = m + 1)
{
    if(plotItemList[m]->title().text() == QString::fromStdString(desiredName[i]))
    {
        plotItemList[m]-> //??? there is no setBrush to use here....I would expect to write...setBrush(QColor(0,0,0,255));
    }
    else
    {
        plotItemList[m]-> //??? there is no setBrush to use here....I would expect to write...setBrush(QColor(130,130,130,50));
    }
}

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---

Added after 30 minutes:

Changing the brush only is fine.

Uwe

I managed to work out how to do it Here is what I did (I found some code online that had your name on it which guided me to the right solution).

QwtPlotItemList plotItemList = myPlot.itemList(QwtPlotItem::Rtti_PlotShape /*added this*/);
for (int m = 0; m < plotItemList.size(); m = m + 1)
{
    QwtPlotShapeItem *shape = static_cast<QwtPlotShapeItem *>( plotItemList[m] );   //added this line
 
    if(plotItemList[m]->title().text() == QString::fromStdString(desiredName[i]))
    {
        shape->setBrush(QColor(0,0,0,255)); //now can set brush to the shape directly
    }
    else
    {
        shape->setBrush(QColor(130,130,130,50)); //now can set brush to the shape directly
    }
}

QwtPlotItemList plotItemList = myPlot.itemList(QwtPlotItem::Rtti_PlotShape /*added this*/);
for (int m = 0; m < plotItemList.size(); m = m + 1)
{
    QwtPlotShapeItem *shape = static_cast<QwtPlotShapeItem *>( plotItemList[m] );   //added this line

    if(plotItemList[m]->title().text() == QString::fromStdString(desiredName[i]))
    {
        shape->setBrush(QColor(0,0,0,255)); //now can set brush to the shape directly
    }
    else
    {
        shape->setBrush(QColor(130,130,130,50)); //now can set brush to the shape directly
    }
}

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