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function isAbove(a: HTMLElement, b: HTMLElement) {
return a.offsetTop + a.clientHeight < b.offsetTop;
}
export function getVerticalNeighbor(
dir: -1 | 1,
items: Iterable<HTMLElement>,
current: HTMLElement,
) {
let candidates: HTMLElement[] = [];
if (dir === -1) {
let adjacentY = Number.MIN_SAFE_INTEGER;
for (const item of items) {
if (!isAbove(item, current)) {
continue;
}
if (item.offsetTop > adjacentY) {
adjacentY = item.offsetTop;
candidates = [item];
} else if (item.offsetTop === adjacentY) {
candidates.push(item);
}
}
} else {
let adjacentY = Number.MAX_SAFE_INTEGER;
for (const item of items) {
if (!isAbove(current, item)) {
continue;
}
if (item.offsetTop < adjacentY) {
adjacentY = item.offsetTop;
candidates = [item];
} else if (item.offsetTop === adjacentY) {
candidates.push(item);
}
}
}
const currentX = current.offsetLeft + 0.5 * current.clientWidth;
let match = candidates[0];
let bestDist = Number.MAX_SAFE_INTEGER;
for (const candidate of candidates) {
const candidateX = candidate.offsetLeft + 0.5 * candidate.clientWidth;
const dist = Math.abs(currentX - candidateX);
if (dist < bestDist) {
bestDist = dist;
match = candidate;
}
}
return match;
}
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