Certain typesetting problems can only be handled by the OTR. Many times, such a problem is solved by communicating with the OTR. Chapter 17 discusses communication from V mode, where certain clues (such as a small piece of glue or kern, or a box with small dimensions) are placed between lines of text. The OTR searches \box255 for clues and, on finding them, modifies the document in the desired way in the vicinity of the clue.
Unable to display preview. Download preview PDF.