Awful flickering with QGridLayout on Mac OS X

[agarny]

Hi,

I am using a QGridLayout to show some widgets which I create on the fly, then delete, create others, etc. This all works fine, but on Mac OS X I get a really awful flickering (despite using setUpdatesEnabled()) while it's all fine on Windows and Linux.

I have created a small Qt project which reproduces the problem (see below). I would really appreciate if someone could tell me whether I missed something obvious or whether it's a 'bug' on Mac OS X.

Cheers, Alan.

Test.pro:

QT += core gui
 
TARGET = Test
TEMPLATE = app
 
SOURCES += main.cpp\
           mainwindow.cpp
 
HEADERS += mainwindow.h

QT += core gui

TARGET = Test
TEMPLATE = app

SOURCES += main.cpp\
           mainwindow.cpp

HEADERS += mainwindow.h

To copy to clipboard, switch view to plain text mode 

main.cpp:

#include <QtGui/QApplication>
#include "mainwindow.h"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
 
    return a.exec();
}

#include <QtGui/QApplication>
#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    
    return a.exec();
}

To copy to clipboard, switch view to plain text mode 

mainwindow.cpp:

#include "mainwindow.h"
 
#include <QGridLayout>
#include <QPushButton>
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)
{
    mWidget = new QWidget(this);
 
    mLayout = new QGridLayout(mWidget);
 
    mWidget->setLayout(mLayout);
 
    populate();
 
    setCentralWidget(mWidget);
 
    this->resize(600, 300);
}
 
void MainWindow::populate()
{
    setUpdatesEnabled(false);
 
    for (int i = 0, iMax = mLayout->count(); i < iMax; ++i) {
        QLayoutItem *item = mLayout->takeAt(0);
 
        delete item->widget();
        delete item;
    }
 
    for (int i = 0; i < 3; ++i)
        for (int j = 0; j < 3; ++j) {
            QPushButton *button = new QPushButton("Click me!", mWidget);
 
            connect(button, SIGNAL(clicked()), this, SLOT(populate()));
 
            mLayout->addWidget(button, i, j);
        }
 
    setUpdatesEnabled(true);
}

#include "mainwindow.h"

#include <QGridLayout>
#include <QPushButton>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)
{
    mWidget = new QWidget(this);

    mLayout = new QGridLayout(mWidget);

    mWidget->setLayout(mLayout);

    populate();

    setCentralWidget(mWidget);

    this->resize(600, 300);
}

void MainWindow::populate()
{
    setUpdatesEnabled(false);

    for (int i = 0, iMax = mLayout->count(); i < iMax; ++i) {
        QLayoutItem *item = mLayout->takeAt(0);

        delete item->widget();
        delete item;
    }

    for (int i = 0; i < 3; ++i)
        for (int j = 0; j < 3; ++j) {
            QPushButton *button = new QPushButton("Click me!", mWidget);

            connect(button, SIGNAL(clicked()), this, SLOT(populate()));

            mLayout->addWidget(button, i, j);
        }

    setUpdatesEnabled(true);
}

To copy to clipboard, switch view to plain text mode 

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
 
class QGridLayout;
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
 
private:
    QWidget *mWidget;
    QGridLayout *mLayout;
 
private Q_SLOTS:
    void populate();
};
 
#endif

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class QGridLayout;

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);

private:
    QWidget *mWidget;
    QGridLayout *mLayout;

private Q_SLOTS:
    void populate();
};

#endif

To copy to clipboard, switch view to plain text mode