Page 199	Table of Contents	Index	Page 201
	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 22. EXTENDED STREAM INPUT

• Clicking or releasing a pointer button
  
  
• Clicking or releasing a pointer button while the pointer is over a presentation
  
  
• Keyboard event (typing a character)

The sheet argument is not evaluated, and must be a symbol that is bound to an input sheet or
stream. If sheet is t, *standard-output* is used. body may have zero or more declarations as
its first forms.

The pointer argument specifies a pointer to track. It defaults to the primary pointer for the
sheet, (stream-primary-pointer sheet).

When the boolean multiple-windows is true, then the pointer will be tracked across multiple
windows, otherwise is will be tracked only in the window corresponding to sheet.

When the boolean transformp is true, then the coordinates supplied to the :pointer-motion
clause will be in the "user" coordinate system rather than in stream coordinates, that is, the
medium's transformation will be applied to the coordinates.

context-type is used to specify the presentation type of presentations that will be "visible" to the
tracking code for purposes of highlighting and for the :presentation, :presentation-button-
press, and :presentation-button-release clauses. Supplying context-type is only useful when
sheet is an output recording stream. context-type defaults to t, meaning that all presentations
are visible.

When highlight is true, tracking-pointer will highlight applicable presentations as the pointer is
positioned over them. highlight defaults to true when any of the :presentation, :presentation-
button-press, or :presentation-button-release clauses is supplied, otherwise it defaults to
false.

The body of tracking-pointer consists of a list of clauses. Each clause is of the form
(clause-keyword arglist . clause-body)
and defines a local function to be run upon occurrence of each type of event. The possible values
for clause-keyword and the associated arglist are:

• :pointer-motion (&key window x y)
  Defines a clause to run whenever the pointer moves. In the clause, window is bound to the
  window in which the motion occurred, and x and y to the coordinates of the pointer. (See
  the keyword argument :transformp below for a description of the coordinate system in
  which x and y are expressed.)
  
  
• :presentation (&key presentation window x y)
  Defines a clause to run whenever the pointer moves over a presentation of the desired type.
  (See the keyword argument :context-type above for a description of how to specify the
  desired type.) In the clause, presentation is bound to the presentation, window to the
  window in which the motion occurred, and x and y to the coordinates of the pointer. (See
  the keyword argument :transformp above for a description of the coordinate system in
  which x and y are expressed.)

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Page 199	Table of Contents	Index	Page 201
	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