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color: text-mode-mixin
color: text-mode%

6 Color

This interface describes how coloring is stopped and started for text that knows how to color itself. It also describes how to query the lexical and s-expression structure of the text.

(send a-color:text start-colorer token-sym->style    
  pairs)  void
  token-sym->style : (-> symbol? string?)
  get-token : 
(or/c (-> input-port?
          (values any/c
                  (or/c false? symbol?)
      (-> input-port?
          (values any/c
                  (or/c false? symbol?)
  pairs : (listof (list/p symbol? symbol?))
Starts tokenizing the buffer for coloring and parenthesis matching.

The token-sym->style argument will be passed the first return symbol from get-token, and it should return the style-name that the token should be colored.

The get-token argument takes an input port and optionally an offset and mode value. When it accepts just an input port, get-token returns the next token as 5 values:

  • An unused value. This value is intended to represent the textual component of the token and may be used as such in the future.

  • A symbol describing the type of the token. This symbol is transformed into a style-name via the token-sym->style argument. The symbols 'white-space and 'comment have special meaning and should always be returned for white space and comment tokens respectively. The symbol 'no-color can be used to indicate that although the token is not white space, it should not be colored. The symbol 'eof must be used to indicate when all the tokens have been consumed.

  • A symbol indicating how the token should be treated by the paren matcher or #f. This symbol should be in the pairs argument.

  • The starting position of the token.

  • The ending position of the token.

When get-token accepts an offset and mode value in addition to an input port, it must also return two extra results, which are a backup distance and new mode. The offset given to get-token can be added to the position of the input port to obtain absolute coordinates within a text stream. The mode argument allows get-token to communicate information from earlier parsing to later. When get-token is called for the beginning on a stream, the mode argument is #f; thereafter, the mode returned for the previous token is provided to get-token for the next token. The mode should not be a mutable value; if part of the stream is re-tokenized, the mode saved from the immediately preceding token is given again to the get-token function. The backup distance returned by get-token indicates the maximum number of characters to back up (counting from the start of the token) and for re-parsing after a change to the editor within the token’s region.

The get-token function is usually be implemented with a lexer using the parser-tools/lex library. The get-token function must obey the following invariants:
  • Every position in the buffer must be accounted for in exactly one token, and every token must have a non-zero width.

  • The token returned by get-token must rely only on the contents of the input port argument plus the mode argument. This constraint means that the tokenization of some part of the input cannot depend on earlier parts of the input except through the mode (and implicitly through the starting positions for tokens).

  • A change to the stream must not change the tokenization of the stream prior to the token immediately preceding the change plus the backup distance. In the following example, this invariant does not hold for a zero backup distance: If the buffer contains

      " 1 2 3

    and the tokenizer treats the unmatched " as its own token (a string error token), and separately tokenizes the 1 2 and 3, an edit to make the buffer look like

      " 1 2 3"

    would result in a single string token modifying previous tokens. To handle these situations, get-token can treat the first line as a single token, or it can precisely track backup distances.

The pairs argument is a list of different kinds of matching parens. The second value returned by get-token is compared to this list to see how the paren matcher should treat the token. An example: Suppose pairs is '((|(| |)|) (|[| |]|) (begin end)). This means that there are three kinds of parens. Any token which has 'begin as its second return value will act as an open for matching tokens with 'end. Similarly any token with '|]| will act as a closing match for tokens with '|[|. When trying to correct a mismatched closing parenthesis, each closing symbol in pairs will be converted to a string and tried as a closing parenthesis.
(send a-color:text stop-colorer [clear-colors])  void
  clear-colors : boolean = #t
Stops coloring and paren matching the buffer.

If clear-colors is true all the text in the buffer will have its style set to Standard.
(send a-color:text force-stop-colorer stop?)  void
  stop? : boolean?
Causes the entire tokenizing/coloring system to become inactive. Intended for debugging purposes only.

stop? determines whether the system is being forced to stop or allowed to wake back up.
(send a-color:text is-stopped?)  boolean?
Indicates if the colorer for this editor has been stopped, or not.

(send a-color:text is-frozen?)  boolean?
Indicates if this editor’s colorer is frozen. See also freeze-colorer and thaw-colorer.

(send a-color:text freeze-colorer)  void
Keep the text tokenized and paren matched, but stop altering the colors.

freeze-colorer will not return until the coloring/tokenization of the entire text is brought up-to-date. It must not be called on a locked text.
(send a-color:text thaw-colorer [recolor    
  retokenize])  void
  recolor : boolean = #t
  retokenize : boolean = #f
Start coloring a frozen buffer again.

If recolor? is #t, the text is re-colored. If it is #f the text is not recolored. When recolor? is #t, retokenize? controls how the text is recolored. #f causes the text to be entirely re-colored before thaw-colorer returns using the existing tokenization. #t causes the entire text to be retokenized and recolored from scratch. This will happen in the background after the call to thaw-colorer returns.

(send a-color:text reset-region start end)  void
  start : natural-number?
  end : (union 'end  natural-number?)
Set the region of the text that is tokenized.

(send a-color:text reset-regions regions)  void
  regions : (listof (list number (union 'end  number)))
Sets the currently active regions to be regions.
(send a-color:text get-regions)
  (listof (list number (union 'end  number)))
This returns the list of regions that are currently being colored in the editor.

(send a-color:text skip-whitespace position    
  comments?)  natural-number?
  position : natural-number?
  direction : (symbols 'forward  'backward)
  comments? : boolean?
Returns the next non-whitespace character.

Starts from position and skips whitespace in the direction indicated by direction. If comments? is true, comments are skipped as well as whitespace. skip-whitespace determines whitespaces and comments by comparing the token type to 'white-space and 'comment.

Must only be called while the tokenizer is started.
(send a-color:text backward-match position 
  (union natural-number? false?)
  position : natural-number?
  cutoff : natural-number?
Skip all consecutive whitespaces and comments (using skip-whitespace) immediately preceding the position. If the token at this position is a close, return the position of the matching open, or #f if there is none. If the token was an open, return #f. For any other token, return the start of that token.

Must only be called while the tokenizer is started.
(send a-color:text backward-containing-sexp position 
  (union natural-number? false?)
  position : natural-number?
  cutoff : natural-number?
Return the starting position of the interior of the (non-atomic) s-expression containing position, or #f is there is none.

Must only be called while the tokenizer is started.
(send a-color:text forward-match position 
  (union natural-number? false?)
  position : natural-number?
  cutoff : natural-number?
Skip all consecutive whitespaces and comments (using skip-whitespace) immediately following position. If the token at this position is an open, return the position of the matching close, or #f if there is none. For any other token, return the end of that token.

Must only be called while the tokenizer is started.
(send a-color:text insert-close-paren position    
  fixup?)  void
  position : natural-number?
  char : char?
  flash? : boolean?
  fixup? : boolean?
The position is the place to put the parenthesis, and char is the parenthesis to be added (e.g., that the user typed). If fixup? is true, the right kind of closing parenthesis will be chosen from the set previously passed to start-colorer – but only if an inserted char would be colored as a parenthesis (i.e., with the 'parenthesis classification). Otherwise, char will be inserted, even if it is not the right kind. If flash? is true, the matching open parenthesis will be flashed.
(send a-color:text classify-position position)  symbol?
  position : natural-number?

Return a symbol for the lexer-determined token type for the token that contains the item after position.

Must only be called while the tokenizer is started.

color:text-mixin : (class? . -> . class?)
  argument extends/implements: text:basic<%>
  result implements: color:text<%>
Adds the functionality needed for on-the-fly coloring and parenthesis matching based on incremental tokenization of the text.

(send a-color:text lock)  void
Overrides lock in editor<%>.

(send a-color:text on-focus)  void
Overrides on-focus in editor<%>.

(send a-color:text after-edit-sequence)  void

(send a-color:text after-set-position)  void

(send a-color:text after-change-style)  void

(send a-color:text on-set-size-constraint)  void

(send a-color:text after-insert)  void
Augments after-insert in text%.

(send a-color:text after-delete)  void
Augments after-delete in text%.

color:text-mode-mixin : (class? . -> . class?)
  argument extends/implements: mode:surrogate-text<%>
  result implements: color:text-mode<%>
This mixin adds coloring functionality to the mode.

(new color:text-mode-mixin 
  [[get-token get-token] 
  [token-sym->style token-sym->style] 
  [matches matches]]) 
  (is-a?/c color:text-mode-mixin)
  get-token : lexer = default-lexer
  token-sym->style : (symbol? . -> . string?)
   = (λ (x) "Standard")
  matches : (listof (list/c symbol? symbol?)) = null
The arguments are passed to start-colorer.
(send a-color:text-mode on-disable-surrogate)  void

(send a-color:text-mode on-enable-surrogate)  void