QGraphicsView wrong initial size of objects

[syrtyr]

Hi!

I'm having trouble with a QGraphicsView. Basically, I want to draw some items (a circle in this example) in a way, that they always fill the complete view.

I did put the QGraphicsView on the main window using qtcreators designer and use it with the following mainwindow.cpp (full example in as attachement):

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPen>
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    circle = new QGraphicsEllipseItem(-10, -10, 20, 20);
    circle->setPen(QPen(Qt::black));
    scene.addItem(circle);
    ui->graphicsView->setScene(&scene);
    ui->graphicsView->fitInView(circle, Qt::KeepAspectRatio);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::resizeEvent(QResizeEvent *e)  // virtual
{
   ui->graphicsView->fitInView(circle, Qt::KeepAspectRatio);
   QMainWindow::resizeEvent(e);
}

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPen>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    circle = new QGraphicsEllipseItem(-10, -10, 20, 20);
    circle->setPen(QPen(Qt::black));
    scene.addItem(circle);
    ui->graphicsView->setScene(&scene);
    ui->graphicsView->fitInView(circle, Qt::KeepAspectRatio);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::resizeEvent(QResizeEvent *e)  // virtual
{
   ui->graphicsView->fitInView(circle, Qt::KeepAspectRatio);
   QMainWindow::resizeEvent(e);
}

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Now what happens is when the window opens, the items do not fill the whole QGraphicsView, they are too small:
initial_view.png
But after the first resize event the fitInView function works as expected and the items fill the whole space:
after_resize.png

Does somebody have an idea why this happens and how to avoid it?

Regards,

syrtyr

[wysota]

In the constructor the size of the view is not determined yet so fitInView will work on bogus data. You should call fitInView from within showEvent().

[syrtyr]

Thanks! That did the trick!