Adjusting QML RowLayout attached properties - qt

Question

I am attempting a simple RowLayout of Rectangles. (See code below.) When I attempt to compile/run this in Qt Creator, I get:
qrc:/main.qml:31 Do not create objects of type Layout
when I attempt to use either Layout.minimumWidth:200 or Layout { minimumWidth:200 }
The Qt documentation for RowLayout shows the first form working. What am I missing?
import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3
ApplicationWindow {
id: window
title: "RB3Jay"
width:1280; height:960
minimumWidth:600; minimumHeight:300
visible: true
Rectangle {
id: pseudocontent
height: parent.height - (header.height + footer.height)
color:'orange'
anchors {
top:header.bottom
bottom:footer.top
left:parent.left
right:parent.right
}
}
header: RowLayout {
id: header
spacing: 0
height: 100
width: parent.width
Rectangle {
color:'red'
Layout {
minimumWidth:200; maximumWidth:200; preferredWidth:200
fillHeight:true
}
}
Rectangle {
color:'green'
Layout {
minimumWidth: 200
preferredWidth: parent.width*0.7
fillWidth:true; fillHeight:true
}
}
Rectangle {
color:'blue'
Layout {
minimumWidth: 200
preferredWidth: parent.width*0.3
fillWidth:true; fillHeight:true
}
}
}
footer: Inspector {
id: footer
height:100
}
}

Answer 1

While the foo { bar: 1; baz: 2 } -syntax works for grouped properties, Foo { } is reserved for creating an instance of QML type Foo. For attached properties, you must use the Foo.bar: 1 -syntax.
Layout is not a creatable type, it only provides attached properties. Therefore you must use the Foo.bar: 1 -syntax.
import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3
ApplicationWindow {
id: window
title: "RB3Jay"
width:1280; height:960
minimumWidth:600; minimumHeight:300
visible: true
Rectangle {
id: pseudocontent
height: parent.height - (header.height + footer.height)
color:'orange'
anchors {
top:header.bottom
bottom:footer.top
left:parent.left
right:parent.right
}
}
header: RowLayout {
id: header
spacing: 0
height: 100
width: parent.width
Rectangle {
color:'red'
Layout.minimumWidth:200
Layout.maximumWidth:200
Layout.preferredWidth:200
Layout.fillHeight:true
}
Rectangle {
color:'green'
Layout.minimumWidth: 200
Layout.preferredWidth: parent.width*0.7
Layout.fillWidth:true; Layout.fillHeight:true
}
Rectangle {
color:'blue'
Layout.minimumWidth: 200
Layout.preferredWidth: parent.width*0.3
Layout.fillWidth:true; Layout.fillHeight:true
}
}
footer: Inspector {
id: footer
height:100
}
}