import ScalingCellSizeAndPositionManager from './ScalingCellSizeAndPositionManager.js'; /** * Helper function that determines when to update scroll offsets to ensure that a scroll-to-index remains visible. * This function also ensures that the scroll ofset isn't past the last column/row of cells. */ export default function updateScrollIndexHelper(_ref) { var cellSize = _ref.cellSize, cellSizeAndPositionManager = _ref.cellSizeAndPositionManager, previousCellsCount = _ref.previousCellsCount, previousCellSize = _ref.previousCellSize, previousScrollToAlignment = _ref.previousScrollToAlignment, previousScrollToIndex = _ref.previousScrollToIndex, previousSize = _ref.previousSize, scrollOffset = _ref.scrollOffset, scrollToAlignment = _ref.scrollToAlignment, scrollToIndex = _ref.scrollToIndex, size = _ref.size, sizeJustIncreasedFromZero = _ref.sizeJustIncreasedFromZero, updateScrollIndexCallback = _ref.updateScrollIndexCallback; var cellCount = cellSizeAndPositionManager.getCellCount(); var hasScrollToIndex = scrollToIndex >= 0 && scrollToIndex < cellCount; var sizeHasChanged = size !== previousSize || sizeJustIncreasedFromZero || !previousCellSize || typeof cellSize === 'number' && cellSize !== previousCellSize; // If we have a new scroll target OR if height/row-height has changed, // We should ensure that the scroll target is visible. if (hasScrollToIndex && (sizeHasChanged || scrollToAlignment !== previousScrollToAlignment || scrollToIndex !== previousScrollToIndex)) { updateScrollIndexCallback(scrollToIndex); // If we don't have a selected item but list size or number of children have decreased, // Make sure we aren't scrolled too far past the current content. } else if (!hasScrollToIndex && cellCount > 0 && (size < previousSize || cellCount < previousCellsCount)) { // We need to ensure that the current scroll offset is still within the collection's range. // To do this, we don't need to measure everything; CellMeasurer would perform poorly. // Just check to make sure we're still okay. // Only adjust the scroll position if we've scrolled below the last set of rows. if (scrollOffset > cellSizeAndPositionManager.getTotalSize() - size) { updateScrollIndexCallback(cellCount - 1); } } } import { bpfrpt_proptype_Alignment } from "../types"; import { bpfrpt_proptype_CellSize } from "../types";