This is the place where write-string and similar functions are captured in order to create an output record. The generic functions include protocol like stream-write-string that are specialized by output recording streams to do the output recording.
stream-text-output-record [Generic Function]
Summary: Returns a text output record for the output recording stream stream suitable for holding characters in the text style text-style . If there is a currently "open" text output record that can hold characters in the specified text style, it is returned. Otherwise a new text output record is created that can hold characters in that text style, and its starting cursor position is set to the cursor position of stream .
stream-close-text-output-record [Generic Function]
Summary: Closes the output recording stream stream 's currently "open" text output record by recording the stream's current cursor position as the ending cursor position of the record and adding the text output record to stream 's current output record by calling stream-add-output-record .
If there is no "open" text output record, stream-close-text-output-record does nothing.
Calling stream-finish-output , stream-force-output , calling redisplay , setting the text cursor position (via stream-set-cursor-position , terpri , or fresh-line ), creating a new output record (for example, via with-new-output-record ), or changing the state of stream-recording-p closes the current text output record.
stream-add-character-output [Generic Function]
Arguments: stream character text-style width height baseline
Summary: Adds the character character to the output recording stream stream 's text output record in the text style text-style . width and height are the width and height of the character in device units. baseline is the new baseline for the stream. stream-add-character-output calls add-character-output-to-text-record .
stream-write-char on an output recording stream will call stream-add-character-output when stream-recording-p is t .
stream-add-string-output [Generic Function]
Arguments: stream string start end text-style width height baseline
Summary: Adds the string string to the output recording stream stream 's text output record in the text style text-style . start and end are integers that specify the substring within string to add to the text output record. width and height are the width and height of the string in device units. baseline is the new baseline for the stream. stream-add-string-output calls add-string-output-to-text-record .
stream-write-string on an output recording stream will call stream-add-string-output when stream-recording-p is t .
Common Lisp Interface Manager 2.0 User's Guide - 7 Aug 2017