@tamagui/react-native-web-lite
Version:
React Native for Web
71 lines (70 loc) • 3.85 kB
JavaScript
function elementsThatOverlapOffsets(offsets, props, getFrameMetrics, zoomScale = 1) {
const itemCount = props.getItemCount(props.data), result = [];
for (let offsetIndex = 0; offsetIndex < offsets.length; offsetIndex++) {
const currentOffset = offsets[offsetIndex];
let left = 0, right = itemCount - 1;
for (; left <= right; ) {
const mid = left + (right - left >>> 1), frame = getFrameMetrics(mid, props), scaledOffsetStart = frame.offset * zoomScale, scaledOffsetEnd = (frame.offset + frame.length) * zoomScale;
if (mid === 0 && currentOffset < scaledOffsetStart || mid !== 0 && currentOffset <= scaledOffsetStart)
right = mid - 1;
else if (currentOffset > scaledOffsetEnd)
left = mid + 1;
else {
result[offsetIndex] = mid;
break;
}
}
}
return result;
}
function newRangeCount(prev, next) {
return next.last - next.first + 1 - Math.max(0, 1 + Math.min(next.last, prev.last) - Math.max(next.first, prev.first));
}
function computeWindowedRenderLimits(props, maxToRenderPerBatch, windowSize, prev, getFrameMetricsApprox, scrollMetrics) {
const itemCount = props.getItemCount(props.data);
if (itemCount === 0)
return { first: 0, last: -1 };
const { offset, velocity, visibleLength, zoomScale = 1 } = scrollMetrics, visibleBegin = Math.max(0, offset), visibleEnd = visibleBegin + visibleLength, overscanLength = (windowSize - 1) * visibleLength, leadFactor = 0.5, fillPreference = velocity > 1 ? "after" : velocity < -1 ? "before" : "none", overscanBegin = Math.max(0, visibleBegin - (1 - leadFactor) * overscanLength), overscanEnd = Math.max(0, visibleEnd + leadFactor * overscanLength);
if (getFrameMetricsApprox(itemCount - 1, props).offset * zoomScale < overscanBegin)
return {
first: Math.max(0, itemCount - 1 - maxToRenderPerBatch),
last: itemCount - 1
};
let [overscanFirst, first, last, overscanLast] = elementsThatOverlapOffsets(
[overscanBegin, visibleBegin, visibleEnd, overscanEnd],
props,
getFrameMetricsApprox,
zoomScale
);
overscanFirst = overscanFirst ?? 0, first = first ?? Math.max(0, overscanFirst), overscanLast = overscanLast ?? itemCount - 1, last = last ?? Math.min(overscanLast, first + maxToRenderPerBatch - 1);
const visible = { first, last };
let newCellCount = newRangeCount(prev, visible);
for (; !(first <= overscanFirst && last >= overscanLast); ) {
const maxNewCells = newCellCount >= maxToRenderPerBatch, firstWillAddMore = first <= prev.first || first > prev.last, firstShouldIncrement = first > overscanFirst && (!maxNewCells || !firstWillAddMore), lastWillAddMore = last >= prev.last || last < prev.first, lastShouldIncrement = last < overscanLast && (!maxNewCells || !lastWillAddMore);
if (maxNewCells && !firstShouldIncrement && !lastShouldIncrement)
break;
firstShouldIncrement && !(fillPreference === "after" && lastShouldIncrement && lastWillAddMore) && (firstWillAddMore && newCellCount++, first--), lastShouldIncrement && !(fillPreference === "before" && firstShouldIncrement && firstWillAddMore) && (lastWillAddMore && newCellCount++, last++);
}
if (!(last >= first && first >= 0 && last < itemCount && first >= overscanFirst && last <= overscanLast && first <= visible.first && last >= visible.last))
throw new Error(
"Bad window calculation " + JSON.stringify({
first,
last,
itemCount,
overscanFirst,
overscanLast,
visible
})
);
return { first, last };
}
function keyExtractor(item, index) {
return typeof item == "object" && item?.key != null ? item.key : typeof item == "object" && item?.id != null ? item.id : String(index);
}
export {
computeWindowedRenderLimits,
elementsThatOverlapOffsets,
keyExtractor,
newRangeCount
};
//# sourceMappingURL=index.js.map