path: root/src/controls/ScrollView.qml

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import QtQuick 2.0
import QtQuick.Controls 1.0
import QtQuick.Controls.Private 1.0

/*!
    \qmltype ScrollView
    \inqmlmodule QtQuick.Controls 1.0
    \ingroup views
    \brief The ScrollView class provides a scrolling view onto another Item.

    A ScrollView can be used either instead of a \l Flickable or to decorate an
    existing Flickable. Depending on the platform it will add scroll bars and
    a content frame.

    Only one Item can be a direct child of the ScrollView and the child is implicitly anchored
    to fill the scroll view.

    Example:
    \code
    ScrollView {
        Image { imageSource: "largeImage.png" }
    }
    \endcode

    In the previous example the Image item will implicitly get scroll behavior as if it was
    used within a \l Flickable. The width and height of the child item will be used to
    define the size of the content area.

    Example:
    \code
    ScrollView {
        ListView {
            ...
        }
    }
    \endcode

    In this case the content size of the ScrollView will simply mirror that of its contained
    \l flickableItem.

*/

FocusScope {
    id: root
    implicitWidth: 200
    implicitHeight: 100

    /*!
        This property tells the scroll view if it should render
        a frame around it's content.

        The default value is \c false
    */
    property bool frameVisible: false

    /*!
        This property controls if there should be a highlight
        around the frame when the ScrollView has input focus.

        The default value is \c false

        \note This property is only applicable on some platforms, such
        as Mac OS.
    */
    property bool highlightOnFocus: false

    /*!
        \qmlproperty Item ScrollView::viewport

        The viewport determines the current "window" on to the contentItem.
        In other words it clips it and the size of the viewport tells you
        how much of the content area is visible.
    */
    property alias viewport: viewportItem

    /*!
        \qmlproperty Item ScrollView::flickableItem

        The flickableItem of the ScrollView. If the contentItem provided
        to the ScrollView is a Flickable, it will be the \l contentItem.
    */
    readonly property alias flickableItem: internal.flickableItem

    /*!
        The contentItem of the ScrollView. This is set by the user.

        Note that the definition of contentItem is somewhat different to that
        of a Flickable, where the contentItem is implicitly created.
    */
    default property Item contentItem

    /*! \internal */
    property Item __scroller: scroller
    /*! \internal */
    property int __scrollBarTopMargin: 0
    /*! \internal */
    property alias horizontalScrollBar: scroller.horizontalScrollBar
    /*! \internal */
    property alias verticalScrollBar: scroller.verticalScrollBar

    /*! \internal */
    onContentItemChanged: {

        if (contentItem.hasOwnProperty("contentY") && // Check if flickable
                contentItem.hasOwnProperty("contentHeight")) {
            internal.flickableItem = contentItem // "Use content if it is a flickable
        } else {
            internal.flickableItem = flickableComponent.createObject(this)
            contentItem.parent = flickableItem.contentItem
        }
        internal.flickableItem.parent = viewportItem
        internal.flickableItem.anchors.fill = viewportItem
    }


    children: Item {
        id: internal

        property Flickable flickableItem

        Binding {
            target: flickableItem
            property: "contentHeight"
            when: contentItem !== flickableItem
            value: contentItem ? contentItem.height : 0
        }

        Binding {
            target: flickableItem
            when: contentItem !== flickableItem
            property: "contentWidth"
            value: contentItem ? contentItem.width : 0
        }

        Connections {
            target: flickableItem

            onContentYChanged:  {
                scroller.blockUpdates = true
                scroller.verticalScrollBar.value = flickableItem.contentY
                scroller.blockUpdates = false
            }

            onContentXChanged:  {
                scroller.blockUpdates = true
                scroller.horizontalScrollBar.value = flickableItem.contentX
                scroller.blockUpdates = false
            }

        }

        anchors.fill: parent

        Component {
            id: flickableComponent
            Flickable {}
        }

        WheelArea {
            id: wheelArea
            parent: flickableItem

            // ### Note this is needed due to broken mousewheel behavior in Flickable.

            anchors.fill: parent

            property int acceleration: 40
            property int flickThreshold: 20
            property double speedThreshold: 3
            property double ignored: 0.001 // ## flick() does not work with 0 yVelocity
            property int maxFlick: 400

            property bool horizontalRecursionGuard: false
            property bool verticalRecursionGuard: false

            horizontalMaximumValue: flickableItem ? flickableItem.contentWidth - viewport.width : 0
            verticalMaximumValue: flickableItem ? flickableItem.contentHeight - viewport.height : 0

            Connections {
                target: flickableItem
                onContentYChanged: {
                    wheelArea.verticalRecursionGuard = true
                    wheelArea.verticalValue = flickableItem.contentY
                    wheelArea.verticalRecursionGuard = false
                }
                onContentXChanged: {
                    wheelArea.horizontalRecursionGuard = true
                    wheelArea.horizontalValue = flickableItem.contentX
                    wheelArea.horizontalRecursionGuard = false
                }
            }

            onVerticalValueChanged: {
                if (!verticalRecursionGuard) {
                    if (flickableItem.contentY < flickThreshold && verticalDelta > speedThreshold) {
                        flickableItem.flick(ignored, Math.min(maxFlick, acceleration * verticalDelta))
                    } else if (flickableItem.contentY > flickableItem.contentHeight
                               - flickThreshold - viewport.height && verticalDelta < -speedThreshold) {
                        flickableItem.flick(ignored, Math.max(-maxFlick, acceleration * verticalDelta))
                    } else {
                        flickableItem.contentY = verticalValue
                    }
                }
            }

            onHorizontalValueChanged: {
                if (!horizontalRecursionGuard)
                    flickableItem.contentX = horizontalValue
            }
        }

        ScrollViewHelper {
            id: scroller
            anchors.fill: parent
            property int frameWidth: frameVisible ? styleitem.pixelMetric("defaultframewidth") : 0
            property bool outerFrame: !frameVisible || !styleitem.styleHint("frameOnlyAroundContents")
            property int scrollBarSpacing: outerFrame ? 0 : styleitem.pixelMetric("scrollbarspacing")
            property int verticalScrollbarOffset: verticalScrollBar.visible && !verticalScrollBar.isTransient ?
                                                      verticalScrollBar.width + scrollBarSpacing : 0
            property int horizontalScrollbarOffset: horizontalScrollBar.visible && !horizontalScrollBar.isTransient ?
                                                        horizontalScrollBar.height + scrollBarSpacing : 0

            StyleItem {
                id: styleitem
                elementType: "frame"
                sunken: true
                visible: frameVisible
                anchors.fill: parent
                anchors.rightMargin: scroller.outerFrame ? 0 : scroller.verticalScrollbarOffset
                anchors.bottomMargin: scroller.outerFrame ? 0 : scroller.horizontalScrollbarOffset
            }

            Item {
                id: viewportItem
                anchors.fill: styleitem
                anchors.margins: scroller.frameWidth
                anchors.rightMargin: scroller.frameWidth + (scroller.outerFrame ? scroller.verticalScrollbarOffset : 0)
                anchors.bottomMargin: scroller.frameWidth + (scroller.outerFrame ? scroller.horizontalScrollbarOffset : 0)
                clip: true
            }
        }
        FocusFrame { visible: highlightOnFocus && area.activeFocus }
    }
}