plasma-framework/declarativeimports/plasmacomponents/platformcomponents/touch/SectionScroller.qml

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import QtQuick 2.0
import "private/SectionScroller.js" as Sections
import org.kde.plasma.core 0.1 as PlasmaCore

/**
 * It's similar to a ScrollBar or a ScrollDecorator.
 * It's interactive and works on ListViews that have section.property set,
 * so its contents are categorized.
 * An indicator will say to what category the user scrolled to.
 *
 * Useful for things like address books or things sorted by date.
 * Don't use with models too big (thousands of items) because implies
 * loading all the items to memory, as well loses precision.
 */
Item {
    id: root

    /**
     * The listview this scroll indicator will work on
     */
    property ListView listView

    onListViewChanged: {
        if (listView && listView.model)
            internal.initDirtyObserver();
    }

    Connections {
        target: listView
        onModelChanged: {
            if (listView && listView.model) {
                internal.initDirtyObserver()
            }
        }
        onMovementStarted: root.opacity = 1
        onMovementEnded: {
            if (!dragArea.pressed) {
                fadeTimer.restart()
            }
        }
    }

    width: 48
    opacity: 0
    Behavior on opacity {
        NumberAnimation {
            duration: 250
        }
    }

    anchors {
        right: listView.right
        top: listView.top
        bottom: listView.bottom
    }

    Timer {
        id: fadeTimer
        interval: 4000
        repeat: false
        running: false
        onTriggered: {
            root.opacity = 0
        }
    }

    RangeModel {
        id: range

        minimumValue: 0
        maximumValue: Math.max(0, listView.contentHeight - listView.height)
        stepSize: 0
        //inverted: true
        positionAtMinimum: handle.height / 2
        positionAtMaximum: root.height - handle.height - handle.height / 2
        value: listView.contentY
        onValueChanged: {
            if (listView.moving) {
                return
            } else {
                listView.contentY = value
            }
        }
        //position: handle.y
        onPositionChanged: {
            if (!dragArea.pressed) {
                handle.y = position
            }
        }
    }

    Rectangle {
        anchors.fill: parent
        color: Qt.rgba(0,0,0,0.3)
    }

    Rectangle {
        id: handle
        width: 6
        height: 6
        color: theme.textColor
        opacity: 0.7
        anchors.horizontalCenter: parent.horizontalCenter
        border {
            width: 1
            color: theme.backgroundColor
        }
        onYChanged: {
            if (dragArea.pressed) {
                range.position = y
            }
            sectionLabel.text = Sections.closestSection(y/listView.height)
        }
    }
    PlasmaCore.FrameSvgItem {
        id: tooltip
        imagePath: "widgets/tooltip"
        width: sectionLabel.paintedWidth + margins.left + margins.right
        height: sectionLabel.paintedHeight + margins.top + margins.bottom
        Label {
            id: sectionLabel
            font.pointSize: theme.defaultFont.pointSize * 1.5
            x: parent.margins.left
            y: parent.margins.top
        }
        y: Math.min(root.height-height, Math.max(0, handle.y - height/2))
        anchors {
            //verticalCenter: handle.verticalCenter
            right: parent.left
        }
        opacity: dragArea.pressed?1:0
        Behavior on opacity {
            NumberAnimation {
                duration: 250
            }
        }
    }

    MouseArea {
        id: dragArea
        anchors.fill: parent
        //enabled: scrollbar.enabled
        drag {
            target: handle
            axis: Drag.YAxis
            minimumY: range.positionAtMinimum
            maximumY: range.positionAtMaximum
        }
        onPressed: {
            mouse.accepted = true
            handle.y = mouse.y
            fadeTimer.running = false
        }
        onReleased: fadeTimer.restart()

    }

    Timer {
        id: dirtyTimer
        interval: 250
        onTriggered: {
            Sections.initSectionData(listView);
            internal.modelDirty = false;
            tooltip.visible = Sections._sections.length > 1
        }
    }
    QtObject {
        id: internal

        property bool modelDirty: false
        function initDirtyObserver() {
            Sections.initSectionData(listView);
            tooltip.visible = Sections._sections.length > 1
            function dirtyObserver() {
                if (!internal.modelDirty) {
                    internal.modelDirty = true;
                    dirtyTimer.running = true;
                }
            }

            if (listView.model.countChanged)
                listView.model.countChanged.connect(dirtyObserver);

            if (listView.model.itemsChanged)
                listView.model.itemsChanged.connect(dirtyObserver);

            if (listView.model.itemsInserted)
                listView.model.itemsInserted.connect(dirtyObserver);

            if (listView.model.itemsMoved)
                listView.model.itemsMoved.connect(dirtyObserver);

            if (listView.model.itemsRemoved)
                listView.model.itemsRemoved.connect(dirtyObserver);
        }
    }
}