Selection-based DOM transforms must not assume a fixed depth

TLDR

Editor features operating on user selections (e.g. splitting paragraphs into multi-column containers) break silently when assuming a fixed DOM nesting depth (.pdf-page-content > p). Document extraction pipelines wrap content in nested positioning wrappers (.pdf-zone > .pdf-region > p), rendering child queries empty. Querying range.commonAncestorContainer dynamically identifies the true shared parent element regardless of nesting depth.

Selection Boundary Engine	DOM Nesting Assumption	Behavior on Pipeline HTML	Transformation Result
Fixed Container Depth	Direct Page Children ( depth = 1 )	Candidate array evaluates empty	Silent Failure (No-op)
Dynamic Common Ancestor	range.commonAncestorContainer	Locates true parent wrapper	100% Correct Split

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Technical implementation: selection-driven operating scope

// Derive transformation target scope dynamically from Selection Range
export function applyColumnSplitToSelection(colsCount, fallbackSurface) {
  const selection = window.getSelection();
  if (!selection.rangeCount) return;
const range = selection.getRangeAt(0);   let ancestorNode = range.commonAncestorContainer;
// Resolve text nodes to parent Element   if (ancestorNode.nodeType === Node.TEXT_NODE) {     ancestorNode = ancestorNode.parentElement;   }
let containerElement = ancestorNode.nodeType === Node.ELEMENT_NODE ? ancestorNode : fallbackSurface;   let candidates = Array.from(containerElement.children);   let selectedChildren = candidates.filter(child => range.intersectsNode(child));
// Single leaf retry: Climb 1 level up if selection collapses inside a single nested node   if (selectedChildren.length < 2 && containerElement.parentElement) {     containerElement = containerElement.parentElement;     candidates = Array.from(containerElement.children);     selectedChildren = candidates.filter(child => range.intersectsNode(child));   }
if (selectedChildren.length < 2) return;
// Perform column split transformation across selected children   redistributeNodesIntoColumns(containerElement, selectedChildren, colsCount); }

Rule of thumb: Derive DOM transformation target scopes dynamically using range.commonAncestorContainer rather than assuming fixed container nesting depths.