[SOLVED] 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@

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&#40;&#41;;

}@

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);

}@

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@

agarny

See http://www.qtcentre.org/threads/49840-Awful-flickering-with-QGridLayout-on-Mac-OS-X?p=223935#post223935 for the 'solution'...