QML content rendering inconsistently with fractional DPI scaling

With fractional DPI scaling active (such as 125%/150% scaling on Windows), QML content may render differently depending on the size of the window. See the example below:

import QtQuick.Window
Window {
        visible: true
        width: 500
        height: 500
        Repeater {
                model: parent.width/2
                Rectangle {
                        x: index*2
                        width: 1
                        color: "red"
                        height: 100
                }
        }
}

This will display a "grating" of thin red vertical lines. Depending on the scaling factor, some rectangles may be wider than others because antialiasing is not enabled. For the experiment, I set OS-level scaling to 150% and resize the window horizontally with the mouse.

Expected behavior: the content is static

Observed behavior: the rectangles alternate between 2px and 1px width.

Suggested fix:

In QQuickWindow::renderSceneGraph replace pixelSize / devicePixelRatio with QSizef(pixelSize) / devicePixelRatio when calling setProjectionMatrixToRect.