add a preference to control whether or not there is an extra

pixel of space in between lines in DrRacket.

This change is based on Matthew's experience having a look
at the font setup on the three platforms.

He writes:
>  * Mac OS X: the convention seems to be to add space between lines.
>   TextEdit, for example, looks like DrRacket: the maze has spaces.
>
>   (I can't find a font that makes the maze look right, actually, even
>   if I adjust the line spacing.)
>
>  * Windows: the convention seems to be that space is built into the
>   font. DrRacket (and SirMail) draw lines more sparsely than Notepad.
>
>   Perhaps consistent with the differing conventions, the height of
>   "Courier New" at 11-pixel size is 14 on Windows, 13 on Mac OS X.
>
>  * Unix: the convention seems to be to add space. DrRacket looks like
>   the default Terminal and Text Editor programs on Ubuntu.
>
>   The maze nevertheless looks right everywhere, because the glyphs
>   extend an extra pixel above the declared bounding box!

original commit: 0d6b82537776ad4bd850e3b7c5cc1bdaa209b865

collects/framework/private/main.rkt

@@ -22,6 +22,10 @@
 
 (application-preferences-handler (λ () (preferences:show-dialog)))
 
+(preferences:set-default 'framework:line-spacing-add-gap?
+                         (not (eq? (system-type) 'windows))
+                         boolean?)
+
 ;; used to time how long it takes to set a preference; the value is not actually used.
 (preferences:set-default 'drracket:prefs-debug #f (λ (x) #t))
 

collects/framework/private/preferences.rkt

@@ -456,7 +456,7 @@ the state transitions / contracts are:
                  (list (string-constant editor-prefs-panel-label) 
                        (string-constant general-prefs-panel-label))
                  (λ (editor-panel)
-                   (make-check editor-panel  'framework:delete-forward? (string-constant map-delete-to-backspace)
+                   (make-check editor-panel 'framework:delete-forward? (string-constant map-delete-to-backspace)
                                not not)
                    (make-check editor-panel 
                                'framework:auto-set-wrap?
@@ -499,6 +499,10 @@ the state transitions / contracts are:
                                  'framework:always-use-platform-specific-linefeed-convention
                                  (string-constant always-use-platform-specific-linefeed-convention)
                                  values values))
+                   (make-check editor-panel
+                               'framework:line-spacing-add-gap?
+                               (string-constant add-spacing-between-lines)
+                               values values)
                    (editor-panel-procs editor-panel))))])
       (add-editor-checkbox-panel)))
   

collects/framework/private/sig.rkt

@@ -168,6 +168,7 @@
   
   (define-signature text-class^
     (basic<%>
+     line-spacing<%>
      first-line<%>
      line-numbers<%>
      foreground-color<%>
@@ -187,6 +188,7 @@
      autocomplete<%>
      
      basic% 
+     line-spacing%
      hide-caret/selection%
      nbsp->space%
      normalize-paste%
@@ -206,6 +208,7 @@
      input-box%
      
      basic-mixin
+     line-spacing-mixin
      first-line-mixin
      line-numbers-mixin
      foreground-color-mixin

collects/framework/private/text.rkt

@@ -56,10 +56,6 @@
     
     (values register-port-name! lookup-port-name)))
 
-
-;; wx: `default-wrapping?', add as the initial value for auto-wrap bitmap,
-;; unless matthew makes it primitive
-
 (define basic<%>
   (interface (editor:basic<%> (class->interface text%))
     highlight-range
@@ -545,6 +541,23 @@
 
 (define (hash-cons! h k v) (hash-set! h k (cons v (hash-ref h k '()))))
 
+(define line-spacing<%> (interface ()))
+
+(define line-spacing-mixin
+  (mixin (basic<%>) (line-spacing<%>)
+    (super-new)
+    (inherit set-line-spacing)
+    ;; this is a field so that the weakly
+    ;; held callback works out properly
+    (define (pref-cb-func sym val)
+      (set-line-spacing (if val 1 0)))
+    (preferences:add-callback 'framework:line-spacing-add-gap?
+                              pref-cb-func
+                              #t)
+    (set-line-spacing (if (preferences:get 'framework:line-spacing-add-gap?)
+                          1
+                          0))))
+
 (define first-line<%>
   (interface ()
     highlight-first-line
@@ -4119,11 +4132,12 @@ designates the character that triggers autocompletion
     (setup-padding)))
 
 (define basic% (basic-mixin (editor:basic-mixin text%)))
-(define hide-caret/selection% (hide-caret/selection-mixin basic%))
-(define nbsp->space% (nbsp->space-mixin basic%))
-(define normalize-paste% (normalize-paste-mixin basic%))
-(define delegate% (delegate-mixin basic%))
-(define wide-snip% (wide-snip-mixin basic%))
+(define line-spacing% (line-spacing-mixin basic%))
+(define hide-caret/selection% (hide-caret/selection-mixin line-spacing%))
+(define nbsp->space% (nbsp->space-mixin line-spacing%))
+(define normalize-paste% (normalize-paste-mixin line-spacing%))
+(define delegate% (delegate-mixin line-spacing%))
+(define wide-snip% (wide-snip-mixin line-spacing%))
 (define standard-style-list% (editor:standard-style-list-mixin wide-snip%))
 (define input-box% (input-box-mixin standard-style-list%))
 (define -keymap% (editor:keymap-mixin standard-style-list%))

collects/scribblings/framework/text.scrbl

@@ -171,6 +171,23 @@
   }
 }
 
+@definterface[text:line-spacing<%> (text:basic<%>)]{
+   Objects implementing this interface adjust their
+   spacing based on the @racket['framework:line-spacing-add-gap?]
+   preference.
+}
+
+@defmixin[text:line-spacing-mixin (text:basic<%>) (text:line-spacing<%>)]{
+  Calls @method[text% set-line-spacing] to either @racket[0] or @racket[1]
+  when an object is created, based
+  on the @racket['framework:line-spacing-add-gap?]
+  preference.
+  
+  Also registers a callback (via @racket[preferences:add-callback]) to call
+  @method[text% set-line-spacing] when the @racket['framework:line-spacing-add-gap?]
+  preference changes.
+}
+
 @definterface[text:first-line<%> (text%)]{
 
   Objects implementing this interface, when @method[text:first-line<%>
@@ -1091,11 +1108,12 @@
 }
 
 @defclass[text:basic% (text:basic-mixin (editor:basic-mixin text%)) ()]{}
-@defclass[text:hide-caret/selection% (text:hide-caret/selection-mixin text:basic%) ()]{}
-@defclass[text:nbsp->space% (text:nbsp->space-mixin text:basic%) ()]{}
-@defclass[text:normalize-paste% (text:normalize-paste-mixin text:basic%) ()]{}
-@defclass[text:delegate% (text:delegate-mixin text:basic%) ()]{}
-@defclass[text:wide-snip% (text:wide-snip-mixin text:basic%) ()]{}
+@defclass[text:line-spacing% (text:line-spacing-mixin text:basic%) ()]{}
+@defclass[text:hide-caret/selection% (text:hide-caret/selection-mixin text:line-spacing%) ()]{}
+@defclass[text:nbsp->space% (text:nbsp->space-mixin text:line-spacing%) ()]{}
+@defclass[text:normalize-paste% (text:normalize-paste-mixin text:line-spacing%) ()]{}
+@defclass[text:delegate% (text:delegate-mixin text:line-spacing%) ()]{}
+@defclass[text:wide-snip% (text:wide-snip-mixin text:line-spacing%) ()]{}
 @defclass[text:standard-style-list% (editor:standard-style-list-mixin text:wide-snip%) ()]{}
 @defclass[text:input-box% (text:input-box-mixin text:standard-style-list%) ()]{}
 @defclass[text:keymap% (editor:keymap-mixin text:standard-style-list%) ()]{}