Creating an Icon-Editor

[Nedec]

Hi,

I know, that paintEvent() repainted the whole area, even if just one pixel changed.

Now, paintEvent() looks like this:

void IconEditor::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
 
    QRect updateRect = event->rect();
    updateRect = QRect(updateRect.topLeft() / zoom, updateRect.size() / zoom);
 
    for(int i = updateRect.left(); i <= updateRect.right(); ++i) {
        if(!image.rect().contains(i, 0)) break;
        for(int j = updateRect.top(); j <= updateRect.bottom(); ++j) {
            if(!image.rect().contains(0, j)) break;
            QRect rect = pixelRect(i, j);
            if(!event->region().intersect(rect).isEmpty()) {
                QColor color = QColor::fromRgba(image.pixel(i, j));
                if(color.alpha() < 255)
                    painter.fillRect(rect, color);
                painter.fillRect(rect, color);
            }
        }
    }
}

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

    QRect updateRect = event->rect();
    updateRect = QRect(updateRect.topLeft() / zoom, updateRect.size() / zoom);

    for(int i = updateRect.left(); i <= updateRect.right(); ++i) {
        if(!image.rect().contains(i, 0)) break;
        for(int j = updateRect.top(); j <= updateRect.bottom(); ++j) {
            if(!image.rect().contains(0, j)) break;
            QRect rect = pixelRect(i, j);
            if(!event->region().intersect(rect).isEmpty()) {
                QColor color = QColor::fromRgba(image.pixel(i, j));
                if(color.alpha() < 255)
                    painter.fillRect(rect, color);
                painter.fillRect(rect, color);
            }
        }
    }
}

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So, only the part that changed is repainted. But it's still not possible to paint a continuous line.

Is there a better way to implement paintEvent()?