paintEvent override

AllForTheGame

Hi everyone...
I'm working on a qt project where I need to redefine the paintEvent function...
I'm using this fonction with a qpainter and this way:

QPainter painter(this);

But, everytime my window get scaled, this widget create a new qpainter and increase the memory size of my program... (140k to 300k)
Is there any way to delete the older QPainter to free the memory???

Thx

mrjj

Hi
Normally you have like this

widget::PaintEvent(xx) {
QPainter painter(this);
}

and painter only lives until paintEvent ends

so maybe its something else that happens when you scale the window?

SGaist

Hi and welcome to devnet,

Can you show the implementation of your paint event ?

Currently, your painter object will be deleted at the end of the function.

AllForTheGame

Here is my function:

void Histogram::paintEvent(QPaintEvent *event)
{
Q_UNUSED(event);

QPainter painter(this);
int i = 0;

if(data.count() > 0)
{
    double barWidth = (width() * 0.9) / (double)data.size();
    uint max = 0;
    double step = 0, height = this->height() * 0.75;
    QLineF horAxe(width() * 0.05, this->height()*0.9, width() * 0.95, this->height()*0.9);
    QLineF verAxe(width() * 0.05, this->height()*0.9, width() * 0.05, this->height()*0.1);

    for(i=0; i < data.size(); i++)
    {
        if (data[i] > max)
            max = data[i];
    }

    painter.drawLine(horAxe);
    painter.drawLine(verAxe);
    painter.drawText(width() * 0.04, this->height() * 0.95, "0");
    painter.drawText(width() * 0.96, this->height() * 0.95, QString::number(data.size() - 1));

    step = height / max;

    for(i=0; i < data.size(); i++)
    {
        double start = this->height()*(0.75 + 0.25 /2) - (data[i] * step);
        double startWidth = (barWidth * i) + barWidth * 0.05 + width() * 0.05;

        painter.fillRect(startWidth, start, barWidth * 0.9, data[i] * step, Qt::green);
        painter.drawRect(startWidth, start, barWidth * 0.9, data[i] * step);
    }
}

}

Normally the object should be destroyed but I don't know cause it gets the widget as a parent, so coud it be possible it never get deleted???

SGaist

Does the memory foot print change each time you make your window bigger ? Or both making it it smaller and bigger triggers that ?

AllForTheGame

Both triggers that

SGaist

Can you run your application through Valgrind to see what it happening with the memory ?