NewlineGroup copy() {
      NewlineGroup copy = new NewlineGroup(myParent, myStart, myBaseIndent, myExtraIndent);
      copy.myLength = myLength;
      for (NewlineGroup child : myChildren) {
        copy.myChildren.add(child.copy());
      }
      for (TextToken token : myTokens) {
        copy.myTokens.add(token.copy());
      }
      copy.myReplacements.addAll(myReplacements);
      return copy;
    }
Recursive reformatting of groups.
If the group's content would take you over the specified preferred line length, then the group is applied.

- This algorithm usually ensures that if a group is applied, then all the group's parents in the tree are also
  applied. This tends to produce a nice structured output with well-placed potential newlines.
- The formatter keeps track of the offset as a result of the reformat at each character in the text buffer, and
  applies them to the bytecode offsets afterwards, so that the line number mappings don't get messed up.
src/org/jetbrains/java/decompiler/util/TextBuffer.java