CODEWITHSUNDEEP
c++performanceqt
Mathieu T
Mathieu T

Reputation: 127

Qt5 more slow than qt4 for draw many pixmaps in TabWidget

I have a widget, and I add 300 pixmaps inside. 

MyWidget::MyWidget( QWidget *parent )
{
    setParent(parent);
    FlowLayout *flowLayout = new FlowLayout(this, 2,2,2);
    setLayout(flowLayout);

    QPixmap* cupcakes = new QPixmap("Resources/Icons/pimpCupcakes.png");
    TilePixmap* tilePximap = new TilePixmap(cupcakes, 0);
    m_buttonGroup = new QButtonGroup(this);

    int id = 0;
    for(int i=0; i<300; ++i)
    {
        TilesetButton* buttonTmp = new TilesetButton(this, tilePximap);
        m_buttonGroup->addButton(buttonTmp, id);
        flowLayout->addWidget(buttonTmp);
        id++;
    }
}

I had this widget in a QTabWidget like this : 

ui.tabWidget->addTab(myWidget, name);

I do this operation with another widget

ui.tabWidget->addTab(myWidget2, name);

in qt4.8, creation (and first draw) need approximatively 4 secondes and after that, switch between tab 1 and 2 is instantaneous.

in qt5, creation (and first draw) need approximatively 4 secondes (so like qt4.8) but after that, switch tab took always 4 secondes between the time when I clicked on the tab and when the signal "currentChanged(int)" emmited.

Qt5 need add some cache configs compared with qt4 ?

(project are identic, just the Qt version is different)

Edit : I do the same test not with pixmap but only with QPushButton* and a simple text on it. and it's the same problems. 3/4 sec latency between my clic and the tab switch.

I look if tabWidget code changed since qt4.8 but I saw nothing which could be the reason of this.

Upvotes: 1

Views: 1202

Answers (1)

dtech
dtech

Reputation: 49289

You can significantly improve your performance by switching to a QGLWidget. Different "paint devices" in Qt have different performance, as seen in this question, the fastest possible solution is to use a QGLWidget with a QGLFramebufferObject.

Also, I think setParent(parent) is not needed, QObject takes care of that and QWidget inherits QObject.

Also, unrelated, but still, the correct term would be "slower" not "more slow".

Good luck!

Upvotes: 2

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