How to draw polyline using vector computed from another class

[PXMYH]

Hi,

I am having trouble draw a polyline from a vector of QPointF which is calculated in another class "getAvgHighTempVec".

Here is my code:



// main.cpp
size_t qpoint_size = c.getAvgHighTempVec().size();
QVector<QPointF> points(qpoint_size);

for(size_t i=0; i < qpoint_size; i++){
points[i].setX(i);
points[i].setY(c.getAvgHighTempVec().at(i));
}

weatherStationGUI.draw(points);



//weatherstationgui.h
namespace Ui {
class weatherstationgui;
}
class weatherstationgui : public QMainWindow
{
Q_OBJECT

public:
explicit weatherstationgui(QWidget *parent = 0);
~weatherstationgui();

void draw( QVector<QPointF> dataIn);

private:
Ui::weatherstationgui *ui;

QVector<QPointF> wellData;

protected:
// paint method
void paintEvent(QPaintEvent *event);
};



//weatherstationgui.cpp
void weatherstationgui::draw(QVector<QPointF> dataIn){
wellData = dataIn;
update();
}

void weatherstationgui::paintEvent(QPaintEvent *event){

// create a painter
QPainter painter(this);

painter.drawPolyline(wellData.data(), static_cast<int>(wellData.size()));
}


In the debugger I can see 'wellData' indeed has the correct QPointF points values, but it just doesn't draw on the main window.

Is there anything wrong with my code?

Thanks

[ChrisW67]

What are typical values in the points array? As you have presented it these values will be treated as equivalent to pixel coordinates.

[PXMYH]

yes, you are absolutely right. The values stored in the vector points are the coordinates. It looks like { (1.6, 0) , (2.3, 1) ...} in debugger.

[ChrisW67]

Your points are being drawn in a few pixels in the top left of the window. You need to scale the values yourself or use a transform on the painter to do it for you.
See Coordinate transforms

[PXMYH]

Thank you Chris! its been there all the time but I chose to ignore it ;)