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.