adjust drracket so check syntax can add its preferences itself

closes PR 13419
(cherry picked from commit 3e3283aeba)

collects/drracket/private/drsig.rkt

@@ -109,8 +109,10 @@
 (define-signature drracket:module-language-tools^ extends drracket:module-language-tools-cm^
   (add-opt-out-toolbar-button
    add-online-expansion-handler
+   register-online-expansion-pref
    
    ;; the below should be hidden from tools
+   get-online-expansion-pref-funcs
    (struct online-expansion-handler (mod-path id local-handler))
    get-online-expansion-handlers
    no-more-online-expansion-handlers))

collects/drracket/private/module-language-tools.rkt

@@ -320,4 +320,10 @@
       [else
        (set! online-expansion-handlers
              (cons (online-expansion-handler mod-path id local-handler)
-                   online-expansion-handlers))])))
+                   online-expansion-handlers))]))
+  
+  (define online-expansion-pref-funcs '())
+  (define (get-online-expansion-pref-funcs) online-expansion-pref-funcs)
+    (define online-expansion-prefs '())
+  (define (register-online-expansion-pref func)
+    (set! online-expansion-pref-funcs (cons func online-expansion-pref-funcs))))

collects/drracket/private/module-language.rkt

@@ -2317,7 +2317,6 @@
        (connect-to-prefs read-choice 'drracket:online-expansion:read-in-defs-errors)
        (connect-to-prefs var-choice 'drracket:online-expansion:variable-errors)
        (connect-to-prefs other-choice 'drracket:online-expansion:other-errors)
-       (preferences:add-check vp
-                              'drracket:syncheck:show-arrows?
-                              (string-constant show-arrows-on-mouseover))
+       (for ([f (in-list (drracket:module-language-tools:get-online-expansion-pref-funcs))])
+         (f vp))
        parent-vp))))

collects/drracket/private/syncheck/gui.rkt

@@ -89,6 +89,11 @@ If the namespace does not, they are colored the unbound color.
    number-between-zero-and-one?))
 (preferences:set-default 'drracket:syncheck:show-arrows? #t boolean?)
 
+(define (syncheck-add-to-online-expansion-prefs-panel vp)
+  (preferences:add-check vp
+                         'drracket:syncheck:show-arrows?
+                         (string-constant show-arrows-on-mouseover)))
+
 (define (syncheck-add-to-preferences-panel parent)
   (color-prefs:build-color-selection-panel parent
                                            lexically-bound-variable-style-pref
@@ -2081,6 +2086,7 @@ If the namespace does not, they are colored the unbound color.
     (add-check-syntax-key-bindings (drracket:rep:get-drs-bindings-keymap))
     (fw:color-prefs:add-to-preferences-panel (string-constant check-syntax)
                                              syncheck-add-to-preferences-panel)
+    (drracket:module-language-tools:register-online-expansion-pref syncheck-add-to-online-expansion-prefs-panel)
     (drracket:language:register-capability 'drscheme:check-syntax-button (flat-contract boolean?) #t)
     (drracket:get/extend:extend-definitions-text make-syncheck-text%)
     (drracket:get/extend:extend-definitions-canvas docs-editor-canvas-mixin)

collects/drracket/tool-lib.rkt

@@ -162,6 +162,14 @@ all of the names in the tools library, for use defining keybindings
     and other tools), but any long running computations may freeze DrRacket's GUI, 
     since this procedure is invoked on DrRacket's eventspace's handler thread.})
  
+ (proc-doc/names
+  drracket:module-language-tools:register-online-expansion-pref
+  (-> (-> (is-a?/c vertical-panel%) void?) void?)
+  (func)
+  @{Registers @racket[func] so that it is called while building the
+    preferences panel. The function is passed a panel that contains 
+    other configuration controls for online expansion.})
+ 
  (proc-doc/names
   drracket:module-language:add-module-language
   (-> any)