On Windows 10 (but I've not tried on other operating systems yet), if I add a frameless window hint to the QQuickView window's flag, I get exactly the window I desired (as expected.)

If I do the same thing and then call setSource( "myqml.qml" ) on that QQuickView, the window will fail to display although the taskbar will show that the application window (the QQuickView.) Note that the setSource call happens after the ::show() call (I tried hiding it, then calling setSource, then unhiding in case there was some window reconstruction issue - but no luck.)

When this happens, the console output shows: "QSGThreadedRenderLoop: expose event received for window QQuickView(0xc6eb8fef68) with invalid geometry: QRect(-1357,226 0x0) on QScreen(0x277c048c960, name=\.\DISPLAY3)"

This is the same display that shows successfully if I don't call setSource.

If the QML file is completely empty or only contains import statements - the window shows properly.
If I add just the following:

Rectangle {
color: "red"
}

The window fails to show.

Interestingly if I give the rectangle a specific size like this:

Rectangle {
width: 100
height: 100
color: "red"
border.color: "black"
border.width: 5
radius: 10
}

Then I do not get the window without a title bar, I get a window exactly the size of the rect and because I gave the corners a radius, I see a white background where the corners would normally be (indicating to me that the window size has shrunk to the size of the rect.)

Anybody know how to fix this?

I would expect the same behavior as when there is a titlebar... Is that wrong?

Thanks!