Showing any window (top-level, children, popup menus, etc.) from Qml on the second monitor of my dual-monitor setup generates the following warning:

QSGThreadedRenderLoop: expose event received for window QQuickWindow(0x36cb450) with invalid geometry: QRect(2800,460 160x160) on QScreen(0x3c6610)

This warning is not output if the window is made visible on the first monitor. Here are the QScreen dimensions reported for a default-constructed QWindow in my app:

Screen availableGeometry: QRect(0,0 1920x1050)
Screen availableVirtualGeometry: QRect(0,0 3840x1080)
Screen availableVirtualSize: QSize(3840, 1080)
Screen virtualGeometry: QRect(0,0 3840x1080)

I've attached a minimal app (screentest.zip) that reproduces the issue. But the following Qml file is sufficient to produce the warning:

import QtQuick 2.5
import QtQuick.Window 2.0

Window {
	visible: true
}