QPainter::drawRect in Qt4.5 is much slower than that in Qt4.3

[bgcrwf]

As title. I wrote a program to test the peformance of QPainter::drawRect.
This program draws 10 rectangles 100 times.
In Qt4.5, the elapsed time is over 1 minute.
But in Qt4.3, the elapsed time is less than 1 second.
By the way, I executed it in Linux X11.
What should I do to fix the problem in Qt4.5?
Thanks a lot.

======================================
class PainterWidget : public QWidget
{
protected:

void paintEvent(QPaintEvent *);

};

void PainterWidget :: paintEvent(QPaintEvent *)
{

// You can change the file name if you need
QBitmap pixmap("xxx.pbm");
QBrush brush(pixmap);
brush.setColor(Qt::red);

QPainter painter(this);
painter.end();

painter.begin(this);
painter.setBrush(brush);
QRect rect;
for (int j=0; j<100; j++) {

for (int i=0; i<10; i++) {

rect.setRect(i*100, 0, 100, 1000);
painter.drawRect(rect);

}

}
painter.end();

}

int main(int argc, char* argv[])
{

QApplication app(argc, argv);

PainterWidget window;
window.resize(1000, 1000);
window.show();

return app.exec();

}

[borisbn]

I think, that I wouldn't help you yet, but...
I tried your code with Qt 4.6.2 at Windows 7 and Visual Studio 2008 ( all of them are not your case )
in Release version of program i had:

213 ms
160 ms
172 ms
162 ms
162 ms
162 ms
162 ms
179 ms
162 ms
175 ms
161 ms

213 ms
160 ms
172 ms
162 ms
162 ms
162 ms
162 ms
179 ms
162 ms
175 ms
161 ms

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P.S. my picture is 80x80 JPEG

void tst::paintEvent( QPaintEvent * )
{
    QTime t;
    t.start();
    // You can change the file name if you need
    QPixmap pixmap( "d:\\Pictures\\shrek_3_-_cat_avatar__80.jpg" );
    QBrush brush( pixmap );
    brush.setColor( Qt::red );
 
    QPainter painter( this );
    //painter.end();
 
    //painter.begin(this);
    painter.setBrush( brush );
    QRect rect;
    for (int j=0; j<100; j++) {
        for (int i=0; i<10; i++) {
            rect.setRect( i*100, 0, 100, 1000 );
            painter.drawRect( rect );
        }
    }
    painter.end();
    qDebug() << t.elapsed();
}

void tst::paintEvent( QPaintEvent * )
{
    QTime t;
    t.start();
    // You can change the file name if you need
    QPixmap pixmap( "d:\\Pictures\\shrek_3_-_cat_avatar__80.jpg" );
    QBrush brush( pixmap );
    brush.setColor( Qt::red );

    QPainter painter( this );
    //painter.end();

    //painter.begin(this);
    painter.setBrush( brush );
    QRect rect;
    for (int j=0; j<100; j++) {
        for (int i=0; i<10; i++) {
            rect.setRect( i*100, 0, 100, 1000 );
            painter.drawRect( rect );
        }
    }
    painter.end();
    qDebug() << t.elapsed();
}

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[bgcrwf]

Dear borisbn,

In line 6 of your program, the QPixmap must be replaced with QBitmap to reproduce the program.
That is because I want to use the bitmap as a mask of the brush.
You can choose a monochrome picture to build the bitmap.

Actually, when I use QPixmap, the drawing performance is excellent (the same as yours).
But when I use QBitmap, the performance degrades a lot.
I think that it should be related to transparent drawing.
By the way, I can reproduce the problem in Qt4.6, too.

Thanks.

[borisbn]

ok, I changed QPixmap to QBitmap, and had this results:

571 
493 
498 
498 
497 
500 
500 
497 
497 
500

571 
493 
498 
498 
497 
500 
500 
497 
497 
500

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image was not clearly showed, time increased by 3 times, but it still not a 1 minute
can you attach your bitmap file xxx.pbm

[bgcrwf]

Hi,

I am glad to upload the image file.
It's in the attachments.

Thanks a lot.

[bgcrwf]

I've tested the peformace of Qt4.5 in windows environment.
It seemed that the problem only happened in Linux X11.

[pherthyl]

Please report: http://bugreports.qt.nokia.com