drawRect not show left and top border line

jinming

Hi,all, I have a class with my custom paintEvent function, and I will draw four black border line,and I find when I adjust window size, it has different effect.The left and top line is missing and right and bottom line is more bigger .Bellow is my code:

void CustomWidgetBase::drawWidget(QPainter* qp)
{
	int w, h;
	w = size().width();
	h = size().height();

	QLinearGradient gradient = QLinearGradient(w, 0, w, h);
	gradient.setColorAt(0, QColor(m_widgetConfig.m_startColor));
	gradient.setColorAt(1, QColor(m_widgetConfig.m_stopColor));
	qp->setPen(Qt::black);
	qp->setBrush(gradient);
	qp->drawRect(0, 0, w-1, h-1);
}

void CustomWidgetBase::paintEvent(QPaintEvent* event)
{
	QPainter qp(this);
	qp.begin(this);
	drawWidget(&qp);
	qp.end();
}

sometime, it shows normal

but when I adjust the window, it shows error

I think it the layout has caused the problem.But I don't know how to solve it.Please help me. Thinks a lot.

Christian Ehrlicher

Works fine for me with Qt6.7

class MyWidget : public QWidget
{
public:
    using QWidget::QWidget;

    void paintEvent(QPaintEvent* event) override
    {
        QPainter qp(this);
        int w, h;
        w = size().width();
        h = size().height();

        QLinearGradient gradient = QLinearGradient(w, 0, w, h);
        gradient.setColorAt(0, QColor(Qt::red));
        gradient.setColorAt(1, QColor(Qt::green));
        qp.setPen(Qt::black);
        qp.setBrush(gradient);
        qp.drawRect(0, 0, w - 1, h - 1);

        qp.end();
    }
};

int main(int argc, char** argv)
{
    QApplication app(argc, argv);

    QWidget w;
    QHBoxLayout* lay = new QHBoxLayout(&w);
    lay->addWidget(new MyWidget);
    w.show();
    return app.exec();
}

jinming

@Christian-Ehrlicher Hi, it seems my screen is high dpi. When I set RoundPreferFloor scale policy, it works fine, but the widget size is less smaller.

int main(int argc, char* argv[]){
    
    QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
//QApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);
QApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::RoundPreferFloor);
    
        QApplication a(argc, argv);
        AppMainWindow w;
        w.show();
        return a.exec();
    }

Christian Ehrlicher

You should create a bug report about this with a minimal, compilable example. I took a short look at the code but can't see any obvious here.