* print a newline before reading if not at column 0

* flush the output before reading in `read-cmdline-syntax'
* rep.ss starts readline only when the input is a terminal

svn: r6128

collects/readline/doc.txt

@@ -18,13 +18,14 @@ You can start MzScheme with
 or you can put the following in your ~/.mzschemerc so that MzScheme
 starts with readline support when appropriate:
 
-  (when (and (regexp-match? #rx"xterm" (getenv "TERM"))
-             (terminal-port? (current-input-port)))
+  (when (regexp-match? #rx"xterm" (getenv "TERM"))
     (dynamic-require '(lib "rep.ss" "readline") #f))
 
-(The first condition rules out running in dumb terminals, eg, inside
-Emacs, and the second condition avoids using it when input is
-redirected.)
+The "rep.ss" module is actually a wrapper around "rep-start.ss", it
+will *not* invoke it if the input port is not a terminal port (eg,
+when the input is redirected from a file).  Still the TERM condition
+above is useful for starting MzScheme in dumb terminals, eg, inside
+Emacs.
 
 The readline history is stored across invocations in MzScheme's
 preferences file, assuming MzScheme exits normally.
@@ -64,7 +65,6 @@ customized with these parameters:
 > keep-blanks
   If #f (the default), blank input lines are not kept in history.
 
-
 The new input port that you get when you require "rep.ss" is a custom
 port that uses readline for all inputs.  The problem is when you want
 to display a prompt and then read some input: readline will get
@@ -75,14 +75,17 @@ line, which is why it has a `prompt' argument.  To use this prompt:
     ...code-that-reads...)
 
 This will make the first call to readline use the prompt, and
-subsequent calls will use an all-spaces prompt of the same length
-(this can happen if you're reading an s-expression).  The normal value
-of `readline-prompt' is #f for an empty prompt (and 'spaces after the
+subsequent calls will use an all-spaces prompt of the same length (for
+example, when you're reading an s-expression).  The normal value of
+`readline-prompt' is #f for an empty prompt (and 'spaces after the
 prompt is used, which is why you should use `parameterize' to restore
 it to #f).
 
-(A proper solution would be to install a custom output port too which
-will keep track of text that is displayed without a trailing newline.)
+A proper solution would be to install a custom output port too which
+keeps track of text that is displayed without a trailing newline.  As
+a cheaper solution, if line-counting is enabled for the terminal's
+output-port, then a newline is printed before reading if the column is
+not 0.  ("rep.ss" enables line-counting for the output port.)
 
 
 Warning

collects/readline/pread.ss

@@ -20,7 +20,13 @@
   (define (save-history)
     (put-preferences '(readline-input-history) (list (reverse local-history))))
 
+  ;; captured now so we don't flush some other output port
+  (define readline-output-port (current-output-port))
+
   (define (readline-bytes/hist p)
+    (when (eq? readline-output-port (current-output-port))
+      (let-values ([(line col pos) (port-next-location readline-output-port)])
+        (when (and col (< 0 col)) (newline))))
     (let ([s (readline-bytes p)])
       (when (and (bytes? s)
                  (or (keep-blanks) (not (zero? (bytes-length s))))
@@ -137,6 +143,7 @@
   (provide read-cmdline-syntax)
   (define (read-cmdline-syntax)
     (define prompt (current-prompt))
+    (flush-output)
     ;; needs to set `readline-prompt' to get a prompt when reading
     (parameterize ([read-accept-reader #t]
                    [readline-prompt prompt])

collects/readline/rep-start.ss

@@ -0,0 +1,9 @@
+;; This module initializes readline unconditionally, "rep.ss" uses it if we're
+;; using a `terminal-port?' for input.
+
+(module rep-start mzscheme
+  (require "pread.ss")
+
+  ;; Change the input port and readline-prompt hook
+  (current-input-port readline-input)
+  (current-prompt-read read-cmdline-syntax))

collects/readline/rep.ss

@@ -1,13 +1,10 @@
-
+;; This is a wrapper around "rep-start.ss" -- use it if we're using a terminal
 (module rep mzscheme
-  (require "pread.ss")
+  (require (lib "runtime-path.ss"))
+  (define-runtime-path rep-start "rep-start.ss")
 
-  ;; Change the input port and readline-prompt hook
-
-  (if (eq? 'stdin (object-name (current-input-port)))
-    (current-input-port readline-input)
-    ;; don't replace some random port
-    (error 'readline-input
-           "invoke this library when the current-input-port is stdin"))
-
-  (current-prompt-read read-cmdline-syntax))
+  (let ([inp (current-input-port)] [outp (current-output-port)])
+    (when (and (eq? 'stdin (object-name inp)) (terminal-port? inp))
+      (dynamic-require rep-start #f)
+      (when (terminal-port? outp)
+        (port-count-lines! outp)))))