In code below onDoubleClicked show window and make requestActivate for it. But window doesn't activate (rather it's activate and later lost activate). If make it only onClicked it work fine. This bug occur on Windows 10. Also I test it on mac and it work fine.

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import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 2.5

Window {
visible: true
width: 640
height: 480
title: qsTr("Hello World")

MouseArea {
anchors.fill: parent
onDoubleClicked:

{ testWindow.show() testWindow.requestActivate() }

}

Text

{ anchors.centerIn: parent text: "Double click me" }

onActiveFocusItemChanged:

{ console.log("root Window:", activeFocusItem) }

Window {
id: testWindow
width: 560
height: 190

onActiveFocusItemChanged:

{ console.log("testWindow:", activeFocusItem, contentItem) }

TextEdit

{ width: 240 text: "<b>Hello</b> <i>World!</i>" font.family: "Helvetica" font.pointSize: 20 color: "blue" focus: true }

}
}