Bad clip region when using 175% High DPI scaling

#include <QtWidgets/QApplication>
#include <QtWidgets/QWidget>
#include <QtGui/QPainter>

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

    // Simulate calling QWidget::update(). Region in widget coordinate.
    QRegion dirtyRegion;
    dirtyRegion += QRect(0, 0, 1387, 4);
    dirtyRegion += QRect(246, 4, 5, 452);
    dirtyRegion += QRect(1163, 4, 5, 452);
    dirtyRegion += QRect(0, 456, 1387, 5);
    dirtyRegion += QRect(246, 461, 5, 100);
    dirtyRegion += QRect(1163, 461, 5, 100);

    // Simulate a widget at (31, 150). Region in tlw's widget coordinate.
    dirtyRegion = dirtyRegion.translated(31, 150);

    // Simulate 175% High DPI scaling.
    QTransform dpiScaling = QTransform::fromScale(1.75, 1.75);
    // QTransform dpiScaling = QTransform::fromScale(2.0, 2.0); // for reference image

    // Simulate final clip region in tlw's backing store in device coordinate.
    QRegion clipRegion = dpiScaling.map(dirtyRegion);

    printf("clipRegion = \n");
    for (QRect r : clipRegion)
        printf("  x=%d, y=%d, w=%d, h=%d\n", r.left(), r.top(), r.width(), r.height());
    printf("\n");
    /*
    clipRegion =
      [0] x=54, y=263, w=2427, h=7
      [1] x=485, y=270, w=9, h=791
      [2] x=2090, y=270, w=9, h=791
      [3] x=54, y=1061, w=2427, h=9
      [4] x=485, y=1069, w=9, h=175
      [5] x=2090, y=1069, w=9, h=175
    Bug: [3].y + [3].h > [4].y

    This breaks clip spans generation: https://github.com/qt/qtbase/blob/4af07d6e54091e7a9e413b92b943eee41cb67bb8/src/gui/painting/qpaintengine_raster.cpp#L3830
      while (lastInBand + 1 < numRects && rects[lastInBand+1].top() == y)
        ++lastInBand;
    The code expects ascending and non-overlapping y. lastInBand should be 5 but got 4.
    Result: [5] is ignored unexpectedly.
    */

    // Expect:
    // ------------
    //    |     |
    // ------------
    //    |     |
    //
    // Result:
    // ------------
    //    |     |
    // ------------
    //    |
    //
    QImage backstore(2500, 1500, QImage::Format_ARGB32_Premultiplied);
    backstore.fill(Qt::white);
    {
        QPainter p(&backstore);
        p.setClipRegion(clipRegion);
        p.fillRect(backstore.rect(), Qt::yellow);
    }
    backstore.save("C:/temp/cross.png");
}