improve indenter

beautiful-racket/br/demo/jsonic/drracket-indenter.rkt

@@ -2,8 +2,28 @@
 (require racket/class describe)
 (provide drracket-indenter)
 
-(define (drracket-indenter txt pos)
-  (define i (char->integer (send txt get-character pos)))
-  (if (zero? i)
-      #f
-      i))
+(define open-braces #f)
+(define indent-width 2)
+
+(define (drracket-indenter txt start-pos)
+  (define fresh-indent? (zero? start-pos))
+  (when fresh-indent? (set! open-braces 0))
+  (define first-pos-in-this-line
+    (for*/first ([pos (in-naturals start-pos)]
+                 [c (in-value (send txt get-character pos))]
+                 #:when (not (char-blank? c)))
+                pos))
+  (define last-pos-in-this-line
+    (send txt find-newline 'forward first-pos-in-this-line))
+  (set! open-braces
+        (+ open-braces
+           (for/sum ([pos (in-range first-pos-in-this-line last-pos-in-this-line)])
+                    (case (send txt get-character pos)
+                      [(#\{) 1]
+                      [(#\}) -1]
+                      [else 0]))))
+  (and (positive? open-braces)
+       (* indent-width
+          (if ((send txt get-character first-pos-in-this-line) . char=? . #\{)
+              (sub1 open-braces)
+              open-braces))))

beautiful-racket/br/demo/jsonic/jsonic-test.rkt

@@ -1,9 +1,9 @@
- #lang br/demo/jsonic
- {
- "string": @$(string-append "foo" "bar")$@,
- {
- "array": @$(range 5)$@,
- "object": @$(hash "k1" "valstring" (format "~a" 42) (hash "k1" (range 10) "k2" 42))$@
- }
- // "bar" :
- }
+#lang br/demo/jsonic
+{
+"string": @$(string-append "foo" "bar")$@,
+{
+"array": @$(range 5)$@,
+"object": @$(hash "k1" "valstring" (format "~a" 42) (hash "k1" (range 10) "k2" 42))$@
+}
+// "bar" :
+}

beautiful-racket/br/demo/jsonic/main.rkt

@@ -1,6 +1,14 @@
 #lang at-exp br/quicklang
 (require "parser.rkt")
 
+#|
+Demonstrate:
++ color lexing
++ indentation
++ toolbar buttons
++ pinpoint errors
+|#
+
 (module+ reader
   (define (read-syntax path port)
     (define parse-tree (parse path (tokenize port)))