[QTBUG-86170] QLabel::setPixmap appears truncated under high screen device pixel ratio - Qt Bug Tracker

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Details

Type: Bug
Status: Closed
Priority: Not Evaluated
Resolution: Done
Affects Version/s: 5.11.3
Fix Version/s: 5.15.2
Component/s: GUI: High-DPI, GUI: Painting
Labels:
None
Environment:
linux x11

Platform/s:

Linux/X11
Commits:
eb98bed4e76bb0fa6bad8474f2f370334cb70f6c (qt/qtbase/dev) dbffdb66544dd0c74a17b92487a79f5781c85057 (qt/qtbase/5.15)

Description

When the device pixel ratio is greater than 1, use QLabel::setPixmap, the content of one pixel on the right and bottom side of the QLabel will be truncated

The following code is an example of mine.

    QApplication app(argc, argv);
    QWidget w;
    QHBoxLayout hlayout;
    QPixmap pix(98, 98);
    QPainter p(&pix);
    
    pix.fill(Qt::black);
    p.setRenderHint(QPainter::Antialiasing);
    p.setBrush(Qt::gray);
    p.setPen(Qt::NoPen);
    p.drawEllipse(0, 0, pix.width(), pix.height());

    w.setLayout(&hlayout);

    QLabel label1;
    pix.setDevicePixelRatio(1.25);
    label1.setPixmap(pix);
    hlayout.addWidget(&label1);

    QLabel label2;
    pix.setDevicePixelRatio(1);
    label2.setPixmap(pix);
    hlayout.addWidget(&label2);

    w.setPalette(QPalette(Qt::red));
    w.show();

Compare the left side and the upper side, and you'll see the right side and the lower side are clearly truncated