Page 152	Table of Contents	Index	Page 154
	Chapters
	1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 A, B, C, D, E

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CHAPTER 16. OUTPUT RECORDING

=> stream-output-history stream [Generic Function]
Returns the history (or top-level output record) for the output recording stream stream.

=> stream-current-output-record stream [Generic Function]
The current "open" output record for the output recording stream stream, the one to which
stream-add-output-record will add a new child record. Initially, this is the same as stream-
output-history. As nested output records are created, this acts as a "stack".

=> (setf stream-current-output-record) record stream [Generic Function]
Sets the current "open" output record for the output recording stream stream to the output
record record.

=> stream-add-output-record stream record [Generic Function]
Adds the output record record to the current output record on the output recording stream
stream (that is, stream-current-output-record).

=> stream-replay stream &optional region [Generic Function]
Directs the output recording stream stream to invoke replay on its output history. Only those
records that overlap the region region (which defaults to the viewport of the stream) are replayed.

16.4.2 Graphics Output Recording

Using draw-line* as an example, calling any of the drawing functions specified in Section 12.5
and Section 12.7 results in the following series of function calls on an output recording stream:

• A program calls draw-line* on arguments sheet, x1, y1, x2, and y2, and perhaps some
  drawing options.
  
  
• draw-line* merges the supplied drawing options into the sheet's medium, and then calls
  medium-draw-line* on the sheet. (Note that a compiler macro could detect the case where
  there are no drawing options or constant drawing options, and do this at compile time.)
  
  
• The :around method for medium-draw-line* on the output recording stream is called.
  This creates an output record with all of the information necessary to replay the output
  record, if stream-recording-p is true. If stream-drawing-p is true, this then does a
  call-next-method. (Note that the call-next-method could be replaced by a call to the
  medium-draw-line* method on the sheet's medium, avoiding the need for a trampolining
  function call.)
  
  
• medium-draw-line* performs the necessary user transformations by applying the medium
  transformation to x1, y1, x2, and y2, and to the clipping region. Then medium-draw-line*
  calls port-draw-line* to do the actual drawing.

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Page 152	Table of Contents	Index	Page 154
	Chapters
	1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 A, B, C, D, E