34 lines
1.4 KiB
JavaScript
34 lines
1.4 KiB
JavaScript
export var SCROLL_DIRECTION_BACKWARD = -1;
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export var SCROLL_DIRECTION_FORWARD = 1;
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export var SCROLL_DIRECTION_HORIZONTAL = 'horizontal';
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export var SCROLL_DIRECTION_VERTICAL = 'vertical';
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/**
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* Calculates the number of cells to overscan before and after a specified range.
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* This function ensures that overscanning doesn't exceed the available cells.
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*/
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export default function defaultOverscanIndicesGetter(_ref) {
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var cellCount = _ref.cellCount,
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overscanCellsCount = _ref.overscanCellsCount,
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scrollDirection = _ref.scrollDirection,
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startIndex = _ref.startIndex,
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stopIndex = _ref.stopIndex;
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// Make sure we render at least 1 cell extra before and after (except near boundaries)
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// This is necessary in order to support keyboard navigation (TAB/SHIFT+TAB) in some cases
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// For more info see issues #625
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overscanCellsCount = Math.max(1, overscanCellsCount);
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if (scrollDirection === SCROLL_DIRECTION_FORWARD) {
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return {
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overscanStartIndex: Math.max(0, startIndex - 1),
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overscanStopIndex: Math.min(cellCount - 1, stopIndex + overscanCellsCount)
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};
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} else {
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return {
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overscanStartIndex: Math.max(0, startIndex - overscanCellsCount),
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overscanStopIndex: Math.min(cellCount - 1, stopIndex + 1)
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};
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}
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}
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import { bpfrpt_proptype_OverscanIndicesGetterParams } from "./types";
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import { bpfrpt_proptype_OverscanIndices } from "./types"; |