QML Dynamic width rectangle from content webengine

[elicat]

Is it possible to dimension the width of a rectangle based on the html content connected to the WebEngine?
Example:
in the html content I have a tree menu that at start up is 300px wide then opening the branches of the tree (the items) the items are expanded and the width also reaches 800px .. there is no setting in the rect that is self-sized ?
I've tried implitchWidth but it doesn't seem to work

	Rectangle {
		id: idRectVerticalMenu
		implicitHeight: viewEngineVerticalMenu.implicitHeight 
		implicitWidth: viewEngineVerticalMenu.implicitWidth
                Layout.minimumWidth : 100
                Layout.maximumWidth: 600
		EngineIndexHtml {
			id: registeredObjectsChannelVerticalMenu
			WebChannel.id: "wiseMan"
		}
		WebEngineView {
			id: viewEngineVerticalMenu
			anchors.fill: parent
			webChannel: channel
                }
	}
. . . .