qwt plot in QWidget is badly scaled

JohnCu

Hi, i have a problem related to badly scaling of a qwt plot. It is automatically located in upper-left corner of a area dedicated to present it. Additionally its size is reduced as well. I want to have it adjusted to whole area.
Here some more information:
Plotting function is a separate class, which inherits QwtPlot class and also is a Q_OBJECT. It uses following variables:

double max_Y_val, min_Y_val;
QwtSymbol* symbol;
QwtPlotGrid* grid;
QwtPlotCurve curve1;
QwtPointSeriesData* myData;
QVector<QPointF> samples;
QwtPlotCanvas* canvas;
QwtPlotPanner* panner;
bool if_update_plot;

Here is the constructor and remaining methods and definitions located in the cpp file:

Plot::Plot(std::string type)
{
	if_update_plot = false;
	setObjectName("plot");
	setAxisTitle(xBottom, "Title");
	setAxisScale(yLeft, 1.0, 15.0);
	QwtPlotCanvas *canvas = new QwtPlotCanvas();
	canvas->setPalette(Qt::white);
	canvas->setBorderRadius(10);

	setCanvas(canvas);

	// grid
	grid = new QwtPlotGrid();
	grid->attach(this);

	zoomer = new QwtPlotZoomer(canvas);
	zoomer->setRubberBandPen(QColor(Qt::black));
	zoomer->setTrackerPen(QColor(Qt::black));
	zoomer->setMousePattern(QwtEventPattern::MouseSelect2,
		Qt::RightButton, Qt::ControlModifier);
	zoomer->setMousePattern(QwtEventPattern::MouseSelect3,
		Qt::RightButton);

	panner = new QwtPlotPanner(canvas);
	panner->setMouseButton(Qt::MidButton);
	this->setAutoReplot(true);
	replot();
}

void Plot::Update_plot(const QString& title, const double X_val[1601 * 16], const double Y_val[1601 * 16], int number)
{
	if_update_plot = true;
	max_Y_val = -200;
	min_Y_val = 0;
	double min = 0, max = 0;
	myData = new QwtPointSeriesData;

	// clear samples
	for (int i = 0; i < samples.length(); i++) {
		samples.pop_back();
	}
	while (samples.length() > 0) {
		samples.pop_back();
	}
	for (int i = 5; i < number; i++) {
		if (Y_val[i] != 0) {
			samples.push_back(QPointF(X_val[i], Y_val[i]));
			if (max_Y_val < Y_val[i]) {
				max_Y_val = Y_val[i];
			}
			if (min_Y_val > Y_val[i]) {
				min_Y_val = Y_val[i];
			}
			max = std::ceil(X_val[i]);
			if (min == 0) {
				min= std::floor(X_val[i]);
			}
		}
	}

	curve1.detach();
	grid = new QwtPlotGrid();
	grid->attach(this);

	myData->setSamples(samples);
	curve1.setStyle(QwtPlotCurve::Lines);
	curve1.setPen(Qt::blue, (2.0), Qt::SolidLine);

	setAxisScale(yLeft, std::floor(min_Y_val), std::ceil(max_Y_val));
	setAxisScale(xBottom, min, max);
	setAxisTitle(yLeft, title);

	curve1.setData(myData);
	curve1.attach(this);
	this->replot();
}

void Plot::detach_curve()
{
	curve1.detach();
}

And in a class (inherits QDialog and also is a Q_OBJECT), which prompts Plot class to generate plot there is a QWidget area, where i want plot to be placed. I placed there in .h file:

Plot* plot = new Plot("title");
bool just_plotted = false;

I also define a slot which is used when data is ready to be plotted. It helps me to decide when to plot. Then in .cpp file there is:

void PlotWindow::plot_results()
{
                // getting data from device
		double x_data[1601], y_data[1601];
		for (int i = 0; i < 1601; i++) {
			x_data[i] = device->x_data[i];
			y_data[i] = device->y_data[i];
		}
		int points_no = device->plot_points_no;

		QHBoxLayout* myLayoutTrans = new QHBoxLayout(ui.widget);
		myLayoutTrans->addWidget(plot);
		ui.widget->setLayout(myLayoutTrans);

                // plot the latest data
		plot->Update_plot("title", x_data, y_data, points_no, false);

		delete myLayoutTrans;
}

I would be grateful if somebody can tell me where is the problem. everything works correctly, except this one thing... After refreshing the problem still occurs.

SGaist

Hi,

@JohnCu said in qwt plot in QWidget is badly scaled:

delete myLayoutTrans;
}

Why are you deleting the layout ?

JohnCu

@SGaist Ok, i moved myLayoutTrans to private variables and in constructor i allocate memory once prior to updating plot. I delete pointer and associated memory in destructor then. Now, plot is presented properly. Thanks for the hint!

SGaist

If you set it up correctly, it will be managed by Qt's parent/child hierarchy and you won't need to delete it in the destructor.