16.4 Reading and Writing Tokens

Sometimes after an accept method has read some input from the user, it may be necessary to insert a modified version of that input back into the input buffer. The following two functions can be used to modify the input buffer:

replace-input[Generic Function]

Arguments: stream new-input &key start end buffer-start rescan

Summary: Replaces the part of the input editing stream stream 's input buffer that extends from buffer-start to its scan pointer with the string new-input . buffer-start defaults to the current input position of stream. start and end can be supplied to specify a subsequence of new-input ; start defaults to 0 and end defaults to the length of new-input .

replace-input queues a rescan by calling queue-rescan if the new input does not match the old output, or if rescan is t .

The returned value is the position in the input buffer.

presentation-replace-input[Generic Function]

Arguments: stream object type view &key buffer-start rescan query-identifier for-context-type

Summary: Like replace-input , except that the new input to insert into the input buffer is obtained by presenting the object object with the presentation type type and view view. buffer-start and rescan are as for replace-input , query-identifier is as for accept , and for-context-type is as for present .

If the object does not have a readable representation (in the Lisp sense), presentation-replace-input may create an "accept result" to represent the object and insert it into the input buffer. For the purposes of input editing, "accept results" must be treated as a single input gesture.

The following two functions are used to read or write a token (that is, a string):


Arguments: stream &key input-wait-handler pointer-button-press-handler click-only

Summary: Reads characters from the interactive steam stream until it encounters a delimiter, activation, or pointer gesture. Returns the accumulated string that was delimited by the delimiter or activation gesture, leaving the delimiter unread.

If the first character of typed input is a quotation mark ( #\" ), then read-token will ignore delimiter gestures until another quotation mark is seen. When the closing quotation mark is seen, read-token will proceed as discussed previously.

If the boolean click-only is t , then no keyboard input is allowed. In that case, read-token will simply ignore any typed characters.

input-wait-handler and pointer-button-press-handler are as for stream-read-gesture . Refer to 15.2.1, The Extended Input Stream Protocol for details.


Arguments: token stream &key acceptably

Summary: write-token is the opposite of read-token ; given the string token, it writes it to the interactive stream stream. If acceptably is t and there are any characters in the token that are delimiter gestures (see with-delimiter-gestures ), then write-token will surround the token with quotation marks ( #\" ).

Typically, present methods will use write-token instead of write-string .

CommonLisp Interface Manager 2.0 User's Guide - 27 Feb 2006