Function getRTLOffsetType

lib/utils/getRTLOffsetType.ts:14–49

(recalculate: boolean = false)

// and then verify that the subsequent "scroll" event matches the negative offset.
// If it does not match, then we can assume a non-standard RTL scroll implementation.
export function getRTLOffsetType(recalculate: boolean = false): RTLOffsetType {
  if (cachedRTLResult === null || recalculate) {
    const outerDiv = document.createElement("div");
    const outerStyle = outerDiv.style;
    outerStyle.width = "50px";
    outerStyle.height = "50px";
    outerStyle.overflow = "scroll";
    outerStyle.direction = "rtl";

    const innerDiv = document.createElement("div");
    const innerStyle = innerDiv.style;
    innerStyle.width = "100px";
    innerStyle.height = "100px";

    outerDiv.appendChild(innerDiv);

    document.body.appendChild(outerDiv);

    if (outerDiv.scrollLeft > 0) {
      cachedRTLResult = "positive-descending";
    } else {
      outerDiv.scrollLeft = 1;
      if (outerDiv.scrollLeft === 0) {
        cachedRTLResult = "negative";
      } else {
        cachedRTLResult = "positive-ascending";
      }
    }

    document.body.removeChild(outerDiv);

    return cachedRTLResult;
  }

  return cachedRTLResult;
}