Function calcGridItemPosition

src/core/calculate.ts:84–164

(
  positionParams: PositionParams,
  x: number,
  y: number,
  w: number,
  h: number,
  dragPosition?: { top: number; left: number } | null,
  resizePosition?: {
    top: number;
    left: number;
    height: number;
    width: number;
  } | null
)

 * @returns Position in pixels
 */
export function calcGridItemPosition(
  positionParams: PositionParams,
  x: number,
  y: number,
  w: number,
  h: number,
  dragPosition?: { top: number; left: number } | null,
  resizePosition?: {
    top: number;
    left: number;
    height: number;
    width: number;
  } | null
): Position {
  const { margin, containerPadding, rowHeight } = positionParams;
  const colWidth = calcGridColWidth(positionParams);

  let width: number;
  let height: number;
  let top: number;
  let left: number;

  // If resizing, use the exact width and height from resize callbacks
  if (resizePosition) {
    width = Math.round(resizePosition.width);
    height = Math.round(resizePosition.height);
  } else {
    // Calculate from grid units
    width = calcGridItemWHPx(w, colWidth, margin[0]);
    height = calcGridItemWHPx(h, rowHeight, margin[1]);
  }

  // If dragging, use the exact left/top from drag callbacks
  if (dragPosition) {
    top = Math.round(dragPosition.top);
    left = Math.round(dragPosition.left);
  } else if (resizePosition) {
    // If resizing, use the exact left/top from resize position
    top = Math.round(resizePosition.top);
    left = Math.round(resizePosition.left);
  } else {
    // Calculate from grid units
    top = Math.round((rowHeight + margin[1]) * y + containerPadding[1]);
    left = Math.round((colWidth + margin[0]) * x + containerPadding[0]);
  }

  // When not dragging or resizing, fix margin inconsistencies caused by rounding.
  // Due to Math.round(), the gap between adjacent items can differ from the
  // expected margin (e.g., 0px or 2px instead of 1px). We fix this by comparing
  // where the next sibling would start vs where this item ends, and adjusting
  // the width/height to maintain consistent margins.
  if (!dragPosition && !resizePosition) {
    if (Number.isFinite(w)) {
      // Calculate where the next column's item would start
      const siblingLeft = Math.round(
        (colWidth + margin[0]) * (x + w) + containerPadding[0]
      );
      // Calculate actual margin: sibling start - (our left + our width)