bbContextMenu details

bbContextMenuDetails.js

// If a text field or textarea's contents are selected, Chromium treats the
// document's selection as if it was a caret selection immediately before the
// text field. This function detects that and returns the text field.
function followedByTextField(range) {
  if (!range.collapsed) return null;
  const node = range.startContainer.childNodes[range.startOffset];
  // Only input and textarea elements have the selectionStart property, and it's
  // only non-null for text fields.
  // Double-equals to match null or undefined.
  if (node?.selectionStart == null) {
    return null;
  } else {
    return node;
  }
}

// The deepest element that contains the entirety of the given range.
// (`range.commonAncestorContainer` might be a Text node, for example.)
function commonAncestorElement(range) {
  let container = range.commonAncestorContainer;
  while (!(container instanceof Element)) {
    container = container.parentNode;
  }
  return container;
}

function getBbContextMenuDetails() {
  const selection = window.getSelection();
  if (selection.rangeCount === 0) {
    return {
      canCopy: false,
      canCut: false,
      canPaste: false,
      selectedText: "",
    };
  }

  // There is at most one selection, so 0 is the one we want.
  const range = selection.getRangeAt(0);

  let collapsed, canEdit;
  const textField = followedByTextField(range);
  if (textField) {
    collapsed = textField.selectionStart === textField.selectionEnd;
    canEdit = !textField.disabled && !textField.readOnly;
  } else {
    collapsed = range.collapsed;
    canEdit = commonAncestorElement(range).isContentEditable;
  }

  return {
    canCopy: !collapsed,
    canCut: !collapsed && canEdit,
    canPaste: canEdit,
    selectedText: selection.toString(),
  };
}