35.12.3 Detached Partial Files

Every partial file has an extent in the master buffer associated with it (called the master extent), marking where in the master buffer the partial file begins and ends. If the text in master buffer that is contained by the extent is deleted, then the extent becomes “detached”, meaning that it no longer refers to a specific region of the master buffer. This can happen either when the text is deleted directly or when the master buffer is reverted. Neither of these should happen in normal usage because the master buffer should generally not be edited directly.

Before doing any operation that references a partial file’s master extent, SXEmacs checks to make sure that the extent is not detached. If this is the case, SXEmacs warns the user of this and the master extent is deleted out of the master buffer, disconnecting the file part. The file part’s filename is cleared and thus must be explicitly specified if the detached file part is to be saved.