Create border with QGraphicsView and QGraphicsView - c++

Question

I've a problem in drawing a border/frame with QGraphicsView and QGraphicsScene. I'd like to create a frame with the same distance for all borders to QGraphicsView border.
I've written some code, but I've obtained a partial result; I was able to create borders for only two sides.
I've tested a bit and the rectangle that I've created has vertices coordinates {0, 0} and {100, 100}, while the scene rect starts from {-10, -10} and goes to {110, 110}, so I don't understand why the rect is not centered since fitInView should cover the entire scene rect.
What I'm doing wrong?
This is the code:
PlotAxes.hpp
#ifndef PLOTAXES_HPP_
#define PLOTAXES_HPP_
#include <QGraphicsObject>
#include <QPen>
#include <QPainter>
class PlotAxes : public QGraphicsObject {
Q_OBJECT
public:
PlotAxes() = delete;
PlotAxes(QGraphicsItem* parent = nullptr) : QGraphicsObject(parent) {}
PlotAxes(const PlotAxes&) = delete;
PlotAxes(PlotAxes&&) = delete;
~PlotAxes() = default;
void setLimits(const QPointF& minXY, const QPointF& maxXY) {
m_minXY = minXY;
m_maxXY = maxXY;
}
void setLimits(const QRectF& r) {
m_minXY = r.topLeft();
m_maxXY = r.bottomRight();
}
public:
QRectF boundingRect() const override {
return QRectF(
m_minXY.x(),
m_minXY.y(),
m_maxXY.x(),
m_maxXY.y()
);
}
void paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QWidget* widget = nullptr) override {
painter->save();
QPen axisPen;
axisPen.setColor(QColor(Qt::GlobalColor::darkRed));
axisPen.setCosmetic(true);
painter->setPen(axisPen);
painter->drawRect(boundingRect());
painter->restore();
}
public:
PlotAxes& operator=(const PlotAxes&) = delete;
PlotAxes& operator=(PlotAxes&&) = delete;
private:
QPointF m_minXY;
QPointF m_maxXY;
};
#endif // !PLOTAXES_HPP_
Plot.hpp
#ifndef PLOT_HPP_
#define PLOT_HPP_
#include "PlotAxes.hpp"
#include <QWidget>
#include <QPointF>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QVBoxLayout>
class Plot : public QWidget {
Q_OBJECT
public:
Plot() = delete;
Plot(QWidget* parent = nullptr) :
QWidget(parent) {
createWidgets();
createLayout();
setMinimumSize(400, 400);
}
Plot(const Plot&) = delete;
Plot(Plot&&) = delete;
~Plot() = default;
void setLimits(const QPointF& minXY, const QPointF& maxXY) {
constexpr double BorderPercentage{ 0.1 };
m_width = maxXY.x() - minXY.x();
m_height = maxXY.y() - minXY.y();
const double originX = minXY.x() - m_width * BorderPercentage;
const double width = (1.0 + BorderPercentage) * m_width;
const double originY = minXY.y() - m_height * BorderPercentage;
const double height = (1.0 + BorderPercentage) * m_height;
m_originX = minXY.x();
m_originY = minXY.y();
m_axes->setLimits(QRectF(m_originX, m_originY, m_width, m_height));
m_scene.setSceneRect(originX, originY, width, height);
auto sr = m_scene.sceneRect();
m_view->fitInView(sr);
}
public:
Plot& operator=(const Plot&) = delete;
Plot& operator=(Plot&&) = delete;
private:
void createWidgets() {
m_view = new QGraphicsView(&m_scene, this);
QRect r = QRect(0, 0, m_view->width(), m_view->height());
m_scene.setSceneRect(r);
m_view->fitInView(m_scene.sceneRect());
m_axes = new PlotAxes(nullptr);
m_scene.addItem(m_axes);
}
void createLayout() {
auto layout = new QVBoxLayout(this);
layout->addWidget(m_view);
}
private:
QGraphicsView* m_view;
QGraphicsScene m_scene;
PlotAxes* m_axes;
double m_originX{ 0.0 };
double m_width{ 0.0 };
double m_originY{ 0.0 };
double m_height{ 0.0 };
};
#endif // !PLOT_HPP_
main.cpp
#include <iostream>
#include <QWidget>
#include <QVBoxLayout>
#include <QApplication>
#include "PlotAxes.hpp"
#include "Plot.hpp"
int main(int argc, char* argv[]) {
QApplication a(argc, argv);
QWidget* w = new QWidget();
Plot* p = new Plot(w);
QVBoxLayout* layout = new QVBoxLayout(w);
layout->addWidget(p);
w->show();
p->setLimits({ 0.0, 0.0 }, { 100.0, 100.0 });
return a.exec();
}
And this is the result:
As you can see the frame it's not centered. How can I fix it?