qt-everywhere-src-5.15.1/qtdeclarative/tests/auto/quick/qquickgridview/data/negativeDisplayMargin.qml

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** This file is part of the test suite of the Qt Toolkit.
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import QtQuick 2.3

ListView {
    id: list
    width: 400
    height: 600
    model: ListModel {
        ListElement { kind: "Bought" }
        ListElement { kind: "Available To Buy" }
    }

    delegate: GridView {
        id: grid
        objectName: "grid"
        height: Math.ceil(count / (width / cellWidth)) * cellHeight / 1
        width: list.width
        interactive: false
        property int count: 50
        cellHeight: 200
        cellWidth: cellHeight
        model: count
        property int createdItems: 0
        property int destroyedItems: 0

        delegate: Item {
            objectName: "delegate"
            width: cellWidth
            height: cellHeight
            Rectangle {
                width: parent.width - 20
                height: parent.height - 20
                anchors.centerIn: parent
                color: Math.random() * 2 > 1 ? "green" : "yellow";
                Text {
                    text: index
                }
                Component.onCompleted: createdItems++
                Component.onDestruction: destroyedItems++
            }
        }

        displayMarginBeginning: 0
        displayMarginEnd: -height

        function updatedDelegateCreationRange() {
            if (list.contentY + list.height <= grid.y) {
                // Not visible
                grid.displayMarginBeginning = 0
                grid.displayMarginEnd = -grid.height
            } else if (grid.y + grid.height <= list.contentY) {
                // Not visible
                grid.displayMarginBeginning = -grid.height
                grid.displayMarginEnd = 0
            } else {
                grid.displayMarginBeginning = -Math.max(list.contentY - grid.y, 0)
                grid.displayMarginEnd = -Math.max(grid.height - list.height - list.contentY + grid.y, 0)
            }
        }

        Component.onCompleted: updatedDelegateCreationRange();
        onHeightChanged: updatedDelegateCreationRange();
        Connections {
            target: list
            onContentYChanged: updatedDelegateCreationRange();
            onHeightChanged: updatedDelegateCreationRange();
        }
    }

    section.property: "kind"
    section.delegate: Text {
        height: 40
        font.pixelSize: 30
        text: section
    }
}