Qt Quick 2 Legend Example

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import QtQuick 2.1
import QtQuick.Layouts 1.0
import QtQuick.Window 2.1
import QtDataVisualization 1.0

Rectangle {
    property Theme3D theme
    property Bar3DSeries series
    property point previousSelection

    id: legendItem
    state: "unselected"

    // Workaround for a layout bug that in some situations causes changing from fully opaque color
    // to a transparent one to use black background instead of what is actually under the items.
    // Having the control always slighthly transparent forces the background to be refreshed
    // properly.
    opacity: 0.999

    RowLayout {
        anchors.fill: parent
        spacing: 0
        clip: true
        Item {
            id: markerSpace
            Layout.minimumWidth: 20
            Layout.minimumHeight: 20
            Layout.fillWidth: true
            Layout.fillHeight: true
            Layout.alignment: Qt.AlignVCenter
            Rectangle {
                x: parent.x + parent.width / 4
                y: parent.y + parent.height / 4
                width: parent.width / 2
                height: width
                border.color: "black"
                color: series.baseColor
            }
        }
        Item {
            height: markerSpace.height
            Layout.fillWidth: true
            Layout.fillHeight: true
            Layout.alignment: Qt.AlignVCenter
            Layout.minimumWidth: 100
            Text {
                anchors.fill: parent
                text: series.name
                verticalAlignment: Text.AlignVCenter
                clip: true
                color: theme.labelTextColor
                font: theme.font
            }
        }
    }

    MouseArea {
        id: mouseArea
        anchors.fill: legendItem
        onClicked: {
            if (legendItem.state === "selected") {
                series.selectedBar = series.invalidSelectionPosition
            } else {
                series.selectedBar = previousSelection
            }
        }
    }

    Connections {
        target: series
        onSelectedBarChanged: {
            if (position != series.invalidSelectionPosition) {
                previousSelection = position
            }
        }
    }

    states: [
        State  {
            name: "selected"
            when: series.selectedBar != series.invalidSelectionPosition
            PropertyChanges {
                target: legendItem
                color: series.singleHighlightColor
            }
        },
        State  {
            name: "unselected"
            when: series.selectedBar == series.invalidSelectionPosition
            PropertyChanges {
                target: legendItem
                color: theme.labelBackgroundColor
            }
        }
    ]
}