qt graphicsscene line subclass - c++

Question

I added a Line subclass from the GraphicsScene class , to draw a line. From MainWindow I call the line function in that class, there are no errors, but the line isn't drawn. I know this must be lack of my c++ skills. But searching didn't help me on this one. What I want is to make different classes for drawing different shapes, instead of polluting the GraphicsScene with all that code, to keep things a bit structured. But what am I doing wrong? I posted my code on github github.com/JackBerkhout/QT_Draw001
line.h
#ifndef LINE_H
#define LINE_H
#include <QMainWindow>
#include <QObject>
#include <QDebug>
#include "graphicsscene.h"
class Line: public GraphicsScene
{
public:
Line();
void drawLine(int x1, int y1, int x2, int y2);
};
#endif // LINE_H
line.cpp
#include "line.h"
Line::Line():
GraphicsScene()
{
}
void Line::drawLine(int x1, int y1, int x2, int y2)
{
// Just draw something by clicking a button
qDebug() << "line"; // This debug message is shown
QColor color;
color.setRgb(128, 0, 255);
QPen pen;
pen.setColor(color);
pen.setWidth(20);
pen.setCapStyle(Qt::RoundCap);
this->addLine(x1, y1, x2, y2, pen); // Didn't draw the line on the scene
}
graphicsscene.cpp
#ifndef GRAPHICSSCENE_H
#define GRAPHICSSCENE_H
#include <QGraphicsScene>
#include <QGraphicsSceneMouseEvent>
#include <QPointF>
#include <QList>
class GraphicsScene : public QGraphicsScene
{
Q_OBJECT
public:
explicit GraphicsScene(QObject *parent = 0);
virtual void mouseDoubleClickEvent(QGraphicsSceneMouseEvent * mouseEvent);
virtual void mouseMoveEvent(QGraphicsSceneMouseEvent * mouseEvent);
virtual void mousePressEvent(QGraphicsSceneMouseEvent * mouseEvent);
virtual void mouseReleaseEvent(QGraphicsSceneMouseEvent * mouseEvent);
QPointF getMousePoint(void);
int getMouseX(void);
int getMouseY(void);
int getNumber(void);
void setNumber(int num);
QPointF mousePoint;
int MouseX, MouseY;
int myNumber;
signals:
void changedMousePosition(QPointF mousePoint);
void changedNumber(int myNumber);
public slots:
private:
QList <QPointF> mousePoints;
// int Number;
};
#endif // GRAPHICSSCENE_H
graphicsscene.cpp
#include "mainwindow.h"
#include "graphicsscene.h"
#include <QDebug>
GraphicsScene::GraphicsScene(QObject *parent) :
QGraphicsScene(parent)
{
this->setBackgroundBrush(Qt::black);
myNumber = 0;
// this-> ->setMouseTracking(true);
}
void GraphicsScene::mouseDoubleClickEvent(QGraphicsSceneMouseEvent * mouseEvent)
{
// mousePoint = mouseEvent->scenePos();
// MouseX = mousePoint.x();
// MouseY = mousePoint.y();
qDebug() << Q_FUNC_INFO << mouseEvent->scenePos();
QGraphicsScene::mouseDoubleClickEvent(mouseEvent);
}
void GraphicsScene::mouseMoveEvent(QGraphicsSceneMouseEvent * mouseEvent)
{
mousePoint = mouseEvent->scenePos();
MouseX = mouseEvent->scenePos().x();
MouseY = mouseEvent->scenePos().y();
emit changedMousePosition(mousePoint);
QGraphicsScene::mouseMoveEvent(mouseEvent);
}
void GraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent * mouseEvent)
{
mousePoint = mouseEvent->scenePos();
MouseX = mouseEvent->scenePos().x();
MouseY = mouseEvent->scenePos().y();
mousePoints.append(mouseEvent->scenePos());
MainWindow *mainWindow = new MainWindow();
mainWindow->Count++;
if(mousePoints.size() == 2)
{
myNumber++;
emit changedNumber(myNumber);
QColor color;
color.setRgb(128, 0, 255);
QPen pen;
pen.setColor(color);
pen.setWidth(20);
pen.setCapStyle(Qt::RoundCap);
this->addLine(mousePoints.at(0).x(), mousePoints.at(0).y(), mousePoints.at(1).x(), mousePoints.at(1).y(), pen);
mousePoints.clear();
}
QGraphicsScene::mousePressEvent(mouseEvent);
}
void GraphicsScene::mouseReleaseEvent(QGraphicsSceneMouseEvent * mouseEvent)
{
mousePoint = mouseEvent->scenePos();
MouseX = mouseEvent->scenePos().x();
MouseY = mouseEvent->scenePos().y();
QGraphicsScene::mouseReleaseEvent(mouseEvent);
}
QPointF GraphicsScene::getMousePoint(void)
{
return mousePoint;
}
int GraphicsScene::getMouseX(void)
{
MouseX = mousePoint.x();
return mousePoint.x();
}
int GraphicsScene::getMouseY(void)
{
MouseY = mousePoint.y();
return mousePoint.y();
}
void GraphicsScene::setNumber(int num)
{
myNumber = num;
}
int GraphicsScene::getNumber(void)
{
return myNumber;
}

Answer 1

You are complicating too much, besides that I think you do not understand what is the purpose of the inheritance, you just have to create a function in GraphicsScene called drawLine and use it when you need it.
GraphicsScene.h
public:
void drawLine(int x1, int y1, int x2, int y2);
GraphicsScene.cpp
void GraphicsScene::drawLine(int x1, int y1, int x2, int y2)
{
QColor color;
color.setRgb(128, 0, 255);
QPen pen;
pen.setColor(color);
pen.setWidth(20);
pen.setCapStyle(Qt::RoundCap);
addLine(x1, y1, x2, y2, pen);
}
And then you call in Mainwindow:
void MainWindow::on_toolButtonDraw_clicked()
{
scene->drawLine(300, 100, 500, 300);
}
When you create a Line object you are creating a new scene and it will be drawn in that scene, so you will not see it.