There's already such preference, which does exactly the same thing. It's 
called #syntaxHighlightingAsYouType.
It looks like its senders have been removed from the image for some 
reason.

Levente

On Sat, 9 Jan 2016, commits at source.squeak.org wrote:

> A new version of ShoutCore was added to project The Inbox:
> http://source.squeak.org/inbox/ShoutCore-kfr.55.mcz
>
> ==================== Summary ====================
>
> Name: ShoutCore-kfr.55
> Author: kfr
> Time: 6 January 2016, 8:49:46.186914 pm
> UUID: bd33aa70-60b2-48ee-adee-31db9e5d3ab7
> Ancestors: ShoutCore-ul.54
>
> Add preference to turn syntax highlighting on or off
>
> =============== Diff against ShoutCore-ul.54 ===============
>
> Item was changed:
>  SHTextStyler subclass: #SHTextStylerST80
>  	instanceVariableNames: 'classOrMetaClass workspace font parser formatAssignments environment sourceMap processedSourceMap pixelHeight attributesByPixelHeight parseAMethod'
> + 	classVariableNames: 'SubduedSyntaxHighlights SyntaxHighlighting SyntaxHighlightingAsYouType SyntaxHighlightingAsYouTypeAnsiAssignment SyntaxHighlightingAsYouTypeLeftArrowAssignment'
> - 	classVariableNames: 'SubduedSyntaxHighlights SyntaxHighlightingAsYouType SyntaxHighlightingAsYouTypeAnsiAssignment SyntaxHighlightingAsYouTypeLeftArrowAssignment'
>  	poolDictionaries: ''
>  	category: 'ShoutCore-Styling'!
>  SHTextStylerST80 class
>  	instanceVariableNames: 'styleTable textAttributesByPixelHeight'!
>
>  !SHTextStylerST80 commentStamp: 'tween 8/27/2004 10:55' prior: 0!
>  I style Smalltalk methods and expressions.
>
>  My 'styleTable' class instance var holds an array ofArrays which control how each token is styled/coloured. See my defaultStyleTable class method for its structure.
>  My styleTable can be changed by either modifying the defaultStyleTable class method and then executing SHTextStylerST80 initialize ; or by giving me a new styleTable through my #styleTable: class method.
>
>  My 'textAttributesByPixelSize' class instance var contains a dictionary of dictionaries.
>  	The key is a pixelSize and the value a Dictionary from token type Symbol to TextAttribute array.
>  	It is created/maintained automatically.
>
>  I also install these 3 preferences when my class initialize method is executed....
>  	#syntaxHighlightingAsYouType  - controls whether methods are styled in browsers
>  	#syntaxHighlightingAsYouTypeAnsiAssignment - controls whether assignments are formatted to be :=
>  	#syntaxHighlightingAsYouTypeLeftArrowAssignment - controls whether assignments are formatted to be _
>
>  I reimplement #unstyledTextFrom: so that TextActions are preserved in the unstyled text
>
>
>
>
>
>
>  !
>  SHTextStylerST80 class
>  	instanceVariableNames: 'styleTable textAttributesByPixelHeight'!
>
> Item was added:
> + ----- Method: SHTextStylerST80 class>>syntaxHighlighting (in category 'preferences') -----
> + syntaxHighlighting
> + 	<preference: 'syntaxHighlighting'
> + 		category: 'browsing'
> + 		description: 'Enable, or disable, Shout - Syntax Highlighting. When enabled, code in Browsers and Workspaces is styled to reveal its syntactic structure.'
> + 		type: #Boolean>
> + 	^SyntaxHighlighting ifNil: [true]!
>
> Item was added:
> + ----- Method: SHTextStylerST80 class>>syntaxHighlighting: (in category 'preferences') -----
> + syntaxHighlighting: aBoolean
> + 	SyntaxHighlighting := aBoolean.!
>
>
>