Qt QGraphicsView Scrolling causes items to randomly disappear - c++

Question

I am having issues with a weird bug which occurs after you adjust the size of a QGraphicsItem.
Here is a YouTube video showing the issue: https://youtu.be/gp1lQTkPf54
In my application, a slider is used to adjust the horizontal zoom of all the regions on the QGraphicsScene. I have made sure to call prepareGeometryChange(); when I am changing the geometry of a region and call update(); but that has not helped. It seems to affect regions that are being rendered out of view from the user.
Code:
mainwindow.cpp
#include "mainwindow.h"
#include "./ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
QGraphicsScene *scene = new QGraphicsScene(this);
ui->graphicsView->setScene(scene);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
RegionGraphicsItem *rgi = new RegionGraphicsItem(ui->graphicsView->scene());
itemList.append(rgi);
ui->graphicsView->scene()->addItem(rgi);
rgi->setHScaleFactor(ui->horizontalSlider->value());
}
void MainWindow::test() {
QWidget test;
test.show();
}
void MainWindow::on_horizontalSlider_valueChanged(int value)
{
for (int i = 0; i < itemList.size(); i++) {
itemList[i]->setHScaleFactor(value);
}
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "regiongraphicsitem.h"
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
QList<RegionGraphicsItem*> itemList;
private slots:
void on_pushButton_clicked();
void on_horizontalSlider_valueChanged(int value);
private:
void test();
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
regiongraphicsitem.cpp
#include "regiongraphicsitem.h"
RegionGraphicsItem::RegionGraphicsItem(QGraphicsScene *_scene) : QGraphicsItem()
{
regionColor = QColor::fromRgb(255,255,255);
setFlags(ItemIsMovable);
waveFormColor = regionColor.darker(80);
outlineColor = QColor("#0f0f0f");
selectedColor = selectedColor.lighter(30);
hScaleFactor = 100;
mainBrush = QBrush(regionColor);
mainPen = QPen(outlineColor, 1);
gridLength = 5;
height = 56;
oldPos = pos();
scene = _scene;
this->prepareGeometryChange();
gridLocation = 5;
setY((0 * 60) + 1);
}
QRectF RegionGraphicsItem::boundingRect() const
{
return QRectF(0, 0, float(gridLength * hScaleFactor), float(height));
}
void RegionGraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
Q_UNUSED(widget);
QRectF rect = boundingRect();
painter->setBrush(mainBrush);
painter->setPen(mainPen);
painter->drawRoundedRect(rect, 5, 5);
painter->setPen(mainPen);
if (selected) {
painter->setBrush(QBrush(mainPen.color()));
painter->drawRoundedRect(QRect(rect.x(), rect.y(), rect.width(), 20), 5, 5);
painter->drawRect(QRect(rect.x(), rect.y() + 5, rect.width(), 15));
}
QFont font = scene->font();
font.setPixelSize(10);
font.setBold(true);
QFontMetricsF fontMetrics(font);
QString text = "TEST";
int heightFont = fontMetrics.boundingRect(text).height();
if (selected) {
painter->setPen(QPen(mainBrush.color(), 1));
}
painter->drawText(5, heightFont + 3, text);
if (pressed == false ) {
setX((gridLocation - 1) * hScaleFactor);
}
}
void RegionGraphicsItem::setHScaleFactor(int value) {
prepareGeometryChange();
hScaleFactor = value;
update();
}
regiongraphicsitem.h
#ifndef RegionGraphicsItem_H
#define RegionGraphicsItem_H
#include <QGraphicsItem>
#include <QColor>
#include <QBrush>
#include <QPen>
#include <QtGui/QPainter>
#include <QGraphicsScene>
#include <QGraphicsSceneMouseEvent>
#include <QDebug>
#include <stdint.h>
class RegionGraphicsItem : public QGraphicsItem
{
public:
RegionGraphicsItem(QGraphicsScene *_scene);
float getGridLocation();
void setHScaleFactor(int value);
protected:
QColor outlineColor;
QColor selectedColor;
QColor regionColor;
QColor waveFormColor;
bool selected;
int penWidth;
int rounded;
QBrush mainBrush;
QBrush waveformBrush;
QPen mainPen;
int height;
float gridLength;
bool pressed = false;
QPointF oldPos, oldMousePos;
int oldTrackIndex;
float gridLocation;
QGraphicsScene *scene;
int oldHScaleFactor;
virtual QRectF boundingRect() const override;
virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
private:
int hScaleFactor;
};
#endif // RegionGraphicsItem_H
Steps to reproduce:
Add a RegionGraphicItem to the QGraphicsScene
Increase the slider until the region is off screen
Decrease the slider and the region will not be visible. <-- This is the issue.