add basic support for #lang line-specific editing

Specifically, the #lang line now selects for a
definitions text surrogate, on top of which several
extensions can be built to, say, more easily add keybindings
or change indenting decisions, etc.

pkgs/drracket-pkgs/drracket-plugin-lib/drracket/private/drsig.rkt

@@ -101,7 +101,11 @@
    module-language-big-defs/ints-interactions-text-mixin
    module-language-big-defs/ints-definitions-text-mixin
    initialize-prefs-panel
-   big-defs/ints-label<%>))
+   big-defs/ints-label<%>
+   
+   change-lang-surrogate-mixin
+   default-surrogate%
+   change-lang-host-mixin))
 
 (define-signature drracket:module-language-tools-cm^
   (frame-mixin

pkgs/drracket-pkgs/drracket/drracket/private/get-extend.rkt

@@ -118,12 +118,13 @@
   (make-extender get-base-interactions-text% 'interactions-text%))
 
 (define (get-base-definitions-text%)
-  (drracket:module-language:module-language-online-expand-text-mixin
-   (drracket:module-language-tools:definitions-text-mixin
-    (drracket:module-language:module-language-big-defs/ints-definitions-text-mixin
-     (drracket:debug:test-coverage-definitions-text-mixin
-      (drracket:debug:profile-definitions-text-mixin
-       (drracket:unit:get-definitions-text%)))))))
+  (drracket:module-language:change-lang-host-mixin
+   (drracket:module-language:module-language-online-expand-text-mixin
+    (drracket:module-language-tools:definitions-text-mixin
+     (drracket:module-language:module-language-big-defs/ints-definitions-text-mixin
+      (drracket:debug:test-coverage-definitions-text-mixin
+       (drracket:debug:profile-definitions-text-mixin
+        (drracket:unit:get-definitions-text%))))))))
 
 (define-values (extend-definitions-text get-definitions-text)
   (make-extender get-base-definitions-text%

pkgs/drracket-pkgs/drracket/drracket/private/modes.rkt

@@ -1,46 +1,54 @@
 #lang racket/unit
-  (require string-constants
-           racket/class
-	   racket/list
-           framework
-           drracket/private/drsig)
+(require string-constants
+         racket/class
+         racket/list
+         framework
+         racket/gui/base
+         drracket/private/drsig)
+
+(import [prefix drracket:module-language: drracket:module-language/int^])
+(export drracket:modes^)
+
+(define-struct mode (name surrogate repl-submit matches-language))
+(define modes (list))
+
+(define (get-modes) modes)
+
+(define (add-mode name surrogate repl-submit matches-language)
+  (let ([new-mode (make-mode name 
+                             surrogate
+                             repl-submit
+                             matches-language)])
+    (set! modes (cons new-mode modes))
+    new-mode))
+
+(define (not-a-language-language? l)
+  (and (not (null? l))
+       (equal? (last l)
+               (string-constant no-language-chosen))))
+
+
+(define (add-initial-modes)
   
-  (import)
-  (export drracket:modes^)
+  ;; must be added first, to make it last in mode list,
+  ;; since predicate matches everything
+  (add-mode 
+   (string-constant scheme-mode)
+   (new racket:text-mode%)
+   (λ (text prompt-position) (racket:text-balanced? text prompt-position))
+   (λ (l) #t))
   
-  (define-struct mode (name surrogate repl-submit matches-language))
-  (define modes (list))
+  (add-mode 
+   (string-constant racket-mode)
+   (new drracket:module-language:default-surrogate%)
+   (λ (text prompt-position) (racket:text-balanced? text prompt-position))
+   (λ (l) (member (string-constant module-language-name) l)))
   
-  (define (get-modes) modes)
-  
-  (define (add-mode name surrogate repl-submit matches-language)
-    (let ([new-mode (make-mode name 
-                               surrogate
-                               repl-submit
-                               matches-language)])
-      (set! modes (cons new-mode modes))
-      new-mode))
-  
-  (define (not-a-language-language? l)
-    (and (not (null? l))
-         (equal? (last l)
-                 (string-constant no-language-chosen))))
-  
-  (define (add-initial-modes)
-    
-    ;; must be added first, to make it last in mode list,
-    ;; since predicate matches everything
-    (add-mode 
-     (string-constant scheme-mode)
-     (new racket:text-mode%)
-     (λ (text prompt-position) (racket:text-balanced? text prompt-position))
-     (λ (l) #t))
-    
-    (add-mode 
-     (string-constant text-mode)
-     #f
-     (λ (text prompt-position) #t)
-     (λ (l) 
-       (and l
-            (or (not-a-language-language? l)
-                (ormap (λ (x) (regexp-match #rx"Algol" x)) l))))))
+  (add-mode 
+   (string-constant text-mode)
+   #f
+   (λ (text prompt-position) #t)
+   (λ (l) 
+     (and l
+          (or (not-a-language-language? l)
+              (ormap (λ (x) (regexp-match #rx"Algol" x)) l))))))

pkgs/drracket-pkgs/drracket/drracket/private/module-language.rkt

@@ -2552,4 +2552,74 @@
                 [tab (in-list (send frame get-tabs))]
                 [v (in-value (send (send tab get-defs) get-filename))]
                 #:when v)
-      v)))
+      v))
+  
+  
+  
+  (define-local-member-name maybe-change-language)
+
+  (define change-lang-host<%> (interface () maybe-change-language))
+  
+  (define change-lang-host-mixin
+    (mixin ((class->interface text%) mode:host-text<%>) (change-lang-host<%>)
+      (inherit set-surrogate)
+      
+      (define current-surrogate-mod #f)
+      (define current-language-end #f)
+      
+      ;; called by the surrogate-mixin to see if the surrogate needs changing if
+      ;; the mode is not the racket language mode, then this doesn't get called.
+      (define/public (maybe-change-language start)
+        (when (or (not current-language-end)
+                  (< start current-language-end))
+          (update-surrogate)))
+      
+      (define/private (update-surrogate)
+        (define defs-port (open-input-text-editor this))
+        ;; need this to count chars, not bytes (in case of non-ASCII
+        ;; in defs before #lang line)
+        (port-count-lines! defs-port)
+        (define get-info
+          (with-handlers ([exn:fail? (λ (x) #f)])
+            (read-language defs-port (λ () #f))))
+        (define-values (line col pos) (port-next-location defs-port))
+        (define new-surrogate-mod
+          (and get-info
+               (get-info 'definitions-text-surrogate #f)))
+        (set! current-language-end pos)
+        (unless (equal? current-surrogate-mod new-surrogate-mod)
+          (set! current-surrogate-mod new-surrogate-mod)
+          (define new-surrogate
+            (and new-surrogate-mod
+                 (with-handlers ([exn:fail? 
+                                  (λ (x)
+                                    (log-error
+                                     (format "Error while loading surrogate; expected to be in ~s\n~a"
+                                             new-surrogate-mod
+                                             (exn-message x)))
+                                    #f)])
+                   (dynamic-require new-surrogate-mod 'surrogate%))))
+          (set-surrogate (new (if new-surrogate
+                                  (change-lang-surrogate-mixin
+                                   new-surrogate)
+                                  default-surrogate%)))))
+      
+      (super-new)))
+  
+  (define change-lang-surrogate-mixin
+    (mixin (mode:surrogate-text<%>) ()
+      (define/override (after-insert ths supr start len)
+        (super after-insert ths supr start len)
+        (when (is-a? ths change-lang-host<%>)
+          (send ths maybe-change-language start)))
+      
+      (define/override (after-delete ths supr start len)
+        (super after-delete ths supr start len)
+        (when (is-a? ths change-lang-host<%>)
+          (send ths maybe-change-language start)))
+      
+      (super-new)))
+  
+  (define default-surrogate%
+    (change-lang-surrogate-mixin
+     racket:text-mode%)))

pkgs/drracket-pkgs/drracket/scribblings/tools/tools.scrbl

@@ -570,16 +570,32 @@ has.
 @index{modes}
 @index{scheme mode}
 @index{racket mode}
+@index{definitions-text-surrogate}
 
-DrRacket provides support for multiple editor modes. Tools
-register modes via
+DrRacket provides support for multiple editor modes based on the
+@tt{#lang} line at the beginning of the editor. If the 
+@onscreen{Modes} submenu of the @onscreen{Edit} menu has
+the @onscreen{Racket} mode chosen (which is the default if the
+Language dialog's ``The Racket Language'' is chosen), then 
+DrRacket calls the language's @racket[get-info] procedure
+(see @racket[read-language] for more about how to set up
+a language's @racket[get-info] procedure) with
+@racket['definitions-text-surrogate]. This is expected to return
+a quoted module path (in the sense of @racket[module-path?]) that
+names a module that exports @racket[surrogate%]. It is expected
+to be bound to a class implementing the @racket[mode:surrogate-text<%>]
+interface. Assuming so, it is used as the surrogate for the definitions
+text.
+
+Additionally, plugins can register modes via
 @racket[drracket:modes:add-mode]. Each mode is
 visible in the @onscreen{Modes} submenu of the @onscreen{Edit}
 menu. Initially, DrRacket only supports two modes: Racket
 mode and text mode.
 
 DrRacket automatically selects a mode for each open
-file based on the file's extension. If the file ends with
+file based on the file's extension (and the language chosen
+as described above). If the file ends with
 @File{.txt}, DrRacket uses text mode. Otherwise, DrRacket
 uses Racket mode.