Macro stepper: allowed languages to enable macro-stepper

svn: r5697

collects/macro-debugger/doc.txt

@@ -14,6 +14,8 @@ OUTLINE
   - syntax-browser.ss
 * Using the macro stepper
 * Using the syntax browser
+* Enabling the macro stepper in other languages
+* Notes for DrScheme language implementors
 
 Introduction
 ============
@@ -272,3 +274,24 @@ properties.
 
 The syntax browser does not preserve the distinction between
 parentheses and square brackets.
+
+
+Notes for DrScheme language implementors
+========================================
+
+The macro stepper works "out of the box" only with certain languages
+out of all the languages available from the DrScheme languages
+menu. For example, the macro stepper is disabled for the teaching
+languages.
+
+An implementor of a new DrScheme language can designate their language
+"macro-steppable" by overriding the 'enable-macro-stepper?' method of
+their implementation of 'drscheme:language:language<%>'. The default
+implementation in the mixin provided by
+'drscheme:language:get-default-mixin' returns false; override this
+method to return true if the macro stepper button should be shown for
+this language.
+
+Note: There is currently no way to customize the behavior of the macro
+stepper for different languages. When enabled, the macro stepper sees
+exactly those terms that pass through the 'current-eval' handler.

collects/macro-debugger/tool.ss

@@ -15,6 +15,13 @@
            (prefix view: "view/prefs.ss")
            (prefix sb: "syntax-browser/embed.ss"))
 
+  (provide tool@
+           language/macro-stepper<%>)
+
+  (define language/macro-stepper<%>
+    (interface ()
+      enable-macro-stepper?))
+
   (define view-base/tool@
     (unit
       (import)
@@ -31,13 +38,18 @@
 
   (define-values/invoke-unit stepper@ (import) (export view:view^))
 
-  (provide tool@)
-
   (define tool@
     (unit (import drscheme:tool^)
           (export drscheme:tool-exports^)
       
-      (define (phase1) (void))
+      (define (phase1)
+        (drscheme:language:extend-language-interface
+         language/macro-stepper<%>
+         (mixin (drscheme:language:language<%>) (language/macro-stepper<%>)
+           (inherit get-language-position)
+           (define/public (enable-macro-stepper?)
+             (macro-stepper-works-for? (get-language-position)))
+           (super-new))))
       (define (phase2) (void))
 
       (define drscheme-eventspace (current-eventspace))
@@ -80,15 +92,16 @@
 	    (inner (void) on-tab-change old new))
 
           (define/public (check-language)
-	    (if (debugger-works-for?
+            (let ([lang
-                 (extract-language-level 
+                   (drscheme:language-configuration:language-settings-language
-                  (send (get-definitions-text) get-next-settings)))
+                    (send (get-definitions-text) get-next-settings))])
+              (if (send lang enable-macro-stepper?)
                   (unless (send macro-debug-button is-shown?)
                           (send macro-debug-panel
                                 add-child macro-debug-button))
                   (when (send macro-debug-button is-shown?)
                         (send macro-debug-panel
-                        delete-child macro-debug-button))))
+                              delete-child macro-debug-button)))))
 
           (send (get-button-panel) change-children
                 (lambda (_)
@@ -180,13 +193,7 @@
 
       ;; Borrowed from mztake/debug-tool.ss
 
-      (define (extract-language-level settings)
+      (define (macro-stepper-works-for? lang)
-	(let* ([language
-                (drscheme:language-configuration:language-settings-language
-                 settings)])
-	  (send language get-language-position)))
-
-      (define (debugger-works-for? lang)
         (let ([main-group (car lang)]
               [second (and (pair? (cdr lang)) (cadr lang))]
               [third (and (pair? (cdr lang)) (pair? (cddr lang)) (caddr lang))])