Fix bug #10129: add positional information to "C-u C-x =".

 lisp/descr-text.el (describe-char): Show information about POS, in
 addition to information about the character at POS.  Improve and
 update the doc string.  Change "code point" to "code point in
 charset", to avoid confusion with the character's Unicode code
 point shown above that.

1 files changed, 35 insertions, 8 deletions

diff --git a/lisp/descr-text.el b/lisp/descr-text.el
index 9aa061be57..d2995ab790 100644
--- a/lisp/descr-text.el
+++ b/lisp/descr-text.el
@@ -376,12 +376,21 @@ This function is semi-obsolete.  Use `get-char-code-property'."
 
 ;;;###autoload
 (defun describe-char (pos &optional buffer)
-  "Describe the character after POS (interactively, the character after point).
-Is POS is taken to be in buffer BUFFER or current buffer if nil.
-The information includes character code, charset and code points in it,
-syntax, category, how the character is encoded in a file,
-character composition information (if relevant),
-as well as widgets, buttons, overlays, and text properties."
+  "Describe position POS (interactively, point) and the char after POS.
+POS is taken to be in BUFFER, or the current buffer if BUFFER is nil.
+The information is displayed in buffer `*Help*'.
+
+The position information includes POS; the total size of BUFFER; the
+region limits, if narrowed; the column number; and the horizontal
+scroll amount, if the buffer is horizontally scrolled.
+
+The character information includes the character code; charset and
+code points in it; syntax; category; how the character is encoded in
+BUFFER and in BUFFER's file; character composition information (if
+relevant); the font and font glyphs used to display the character;
+the character's canonical name and other properties defined by the
+Unicode Data Base; and widgets, buttons, overlays, and text properties
+relevant to POS."
   (interactive "d")
   (unless (buffer-live-p buffer) (setq buffer (current-buffer)))
   (let ((src-buf (current-buffer)))
@@ -511,7 +520,25 @@ as well as widgets, buttons, overlays, and text properties."
             (setq composition nil)))
 
       (setq item-list
-            `(("character"
+            `(("position"
+               ,(let* ((beg      (point-min))
+                       (end      (point-max))
+                       (total    (buffer-size))
+                       (percent  (if (> total 50000) ; Avoid overflow multiplying by 100
+                                     (/ (+ (/ total 200) (1- pos))  (max (/ total 100) 1))
+                                   (/ (+ (/ total 2) (* 100 (1- pos)))  (max total 1))))
+                       (hscroll  (if (= (window-hscroll) 0)
+                                     ""
+                                   (format ", Hscroll: %d" (window-hscroll))))
+                       (col      (current-column)))
+                  (if (or (/= beg 1)  (/= end (1+ total)))
+                      (format "%d of %d (%d%%), restriction: <%d-%d>, column: %d%s"
+                              pos total percent col beg end hscroll)
+                    (if (= pos end)
+                        (format "%d of %d (EOB), column: %d%s" pos total col hscroll)
+                      (format "%d of %d (%d%%), column: %d%s"
+                              pos total percent col hscroll)))))
+              ("character"
                ,(format "%s (displayed as %s) (codepoint %d, #o%o, #x%x)"
 			char-description
                         (apply 'propertize char-description
@@ -522,7 +549,7 @@ as well as widgets, buttons, overlays, and text properties."
                   ,(symbol-name charset)
                   'type 'help-character-set 'help-args '(,charset))
                ,(format "(%s)" (charset-description charset)))
-              ("code point"
+              ("code point in charset"
                ,(let ((str (if (integerp code)
                                (format (if (< code 256) "0x%02X" "0x%04X")
                                        code)