Function createDataSource

tests/ListViewComponents/LayoutTest.ts:1198–1236

(data, requests)

    generate("testMaximumRowsOrColumnsVertical", "GridLayout", testMaximumRowsOrColumnsVertical);

    function createDataSource(data, requests) {
        var dataSource = {
            itemsFromIndex: function (index, countBefore, countAfter) {
                return new WinJS.Promise(function (complete, error) {
                    if (index >= 0 && index < data.length) {
                        var startIndex = Math.max(0, index - countBefore),
                            endIndex = Math.min(index + countAfter, data.length - 1),
                            size = endIndex - startIndex + 1;

                        var items = [];
                        for (var i = startIndex; i < startIndex + size; i++) {
                            items.push({
                                key: i.toString(),
                                data: data[i]
                            });
                            requests.push(i);
                        }

                        var retVal = {
                            items: items,
                            offset: index - startIndex,
                            totalCount: data.length,
                            absoluteIndex: index
                        };

                        complete(retVal);
                    } else {
                        complete({});
                    }
                });
            },

            getCount: function () {
                return WinJS.Promise.wrap(data.length);
            }
        };

        return new WinJS.UI.ListDataSource(dataSource);
    }

    var generateRecalculateItemPosition = function (layoutName) {
        LayoutTestsExtra.prototype["testRecalculateItemPosition" + (layoutName == "GridLayout" ? "" : layoutName)] = function (complete) {