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#include <QApplication>
#include <QWidget>
#include <QPainter>
#include <QElapsedTimer>

class Widget : public QWidget
{
public:
	Widget();

protected:
	void timerEvent(QTimerEvent *event);
	void paintEvent(QPaintEvent *);

private:
	QElapsedTimer elapsedTimer;
	int timerId;
	int elapsedTime1, elapsedTime2;
    bool isFinished1, isFinished2, isFinished3;
    int i, x1, x2, y1, y2;
};

Widget::Widget()
{
	setAutoFillBackground(true);
	setPalette(Qt::white);

	timerId = startTimer(1);
	elapsedTimer.start();

    i=0; x1=0; x2=0;
    isFinished1 = isFinished2 = isFinished3 = false;
}

void Widget::timerEvent(QTimerEvent* /* event */)
{
	update();
}

void Widget::paintEvent(QPaintEvent *)
{
	QPainter painter(this);

	if (i > 0 && i < 800)
	{
		y1 = 10;
		painter.setFont(QFont("Arial", 14.0));
		painter.drawText(x1, y1 += 30, "Test 1");
		painter.drawText(x1, y1 += 30, "row 01");
		painter.drawText(x1, y1 += 30, "row 02");
		painter.drawText(x1, y1 += 30, "row 03");
		painter.drawText(x1, y1 += 30, "row 04");
		painter.drawText(x1, y1 += 30, "row 05");
		painter.drawText(x1, y1 += 30, "row 06");
		painter.drawText(x1, y1 += 30, "row 07");
		painter.drawText(x1, y1 += 30, "row 08");
		painter.drawText(x1, y1 += 30, "row 09");
		painter.drawText(x1, y1 += 30, "row 10");
		painter.drawText(x1, y1 += 30, "row 11");
		painter.drawText(x1, y1 += 30, "row 12");
		x1++;
		
		elapsedTime1 = elapsedTimer.elapsed();
	}
	else if (i > 800 && i < 1600)
	{
      // 'With Qt 5.6.0 and later: 'Test2' is about 9 times slower than 'Test1' 
      // (45 seconds on my system)

      // 'With Qt 5.5.1 and earlier versions 'Test2' is same fast as 'Test1' 
      // (5 seconds on my system)

		isFinished1 = true;

		y2 = 300;
		painter.setFont(QFont("Arial", 14));
		painter.drawText(x2, y2 += 30, "Test 2");
		painter.setFont(QFont("Caladea", 14));
		painter.drawText(x2, y2 += 30, "row 01");
		painter.setFont(QFont("Tomaha", 14));
		painter.drawText(x2, y2 += 30, "row 02");
		painter.setFont(QFont("Consolas", 14));
		painter.drawText(x2, y2 += 30, "row 03");
		painter.setFont(QFont("Calibri", 14));
		painter.drawText(x2, y2 += 30, "row 04");
		painter.setFont(QFont("Impact", 14));
		painter.drawText(x2, y2 += 30, "row 05");
		painter.setFont(QFont("Courier New", 14));
		painter.drawText(x2, y2 += 30, "row 06");
		painter.setFont(QFont("Gorgia", 14));
		painter.drawText(x2, y2 += 30, "row 07");
		painter.setFont(QFont("Verdana", 14));
		painter.drawText(x2, y2 += 30, "row 08");
		painter.setFont(QFont("Times New Roman", 14));
		painter.drawText(x2, y2 += 30, "row 09");
		painter.setFont(QFont("Microsoft Sans Serif", 14));
		painter.drawText(x2, y2 += 30, "row 10");
		painter.setFont(QFont("Segoe UI", 14));
		painter.drawText(x2, y2 += 30, "row 11");
		painter.setFont(QFont("Trebuchet MS", 14));
		painter.drawText(x2, y2 += 30, "row 12");
		x2++;

		elapsedTime2 = elapsedTimer.elapsed();
	}
	else if (i > 1600)
	{
		isFinished2 = true;
	}
	i++;
	
	if (isFinished1)
	{
		painter.setFont(QFont("Arial", 12.0, QFont::Bold));
		painter.drawText(QPoint(200, 150), "'Test1' elapsed time in seconds: " + QString::number(elapsedTime1/1000.0));
	}
	if (isFinished2)
	{
        painter.drawText(QPoint(200, 430), "'Test2' elapsed time in seconds: " + QString::number((elapsedTime2-elapsedTime1)/1000.0));
		isFinished3 = true;
	}
	if (isFinished3)
	{
        painter.setFont(QFont("Arial", 11.0));
        painter.drawText(QPoint(200, 620), "On Windows Desktop with Qt 5.4.2, Qt 5.5.0 and Qt 5.5.1 Test1 and Test2 are both equally fast.");
        painter.drawText(QPoint(200, 650), "On Windows Desktop with Qt 5.6.0, Qt 5.6.1 and Qt 5.7.0 Test2 is approx 9 times slower than Test1 !");
        painter.drawText(QPoint(200, 680), "No matter if compiled with MinGW 32 bit or Microsoft Compiler 32 or 64 bit");
        killTimer(timerId);
	}
}

int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
	Widget widget;
	widget.showMaximized();
	return app.exec();
}