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+;;; warnings.el --- log and display warnings
+
+;; Copyright (C) 2002 Free Software Foundation, Inc.
+
+;; Maintainer: FSF
+;; Keywords: internal
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;; This file implements the entry points `warn', `lwarn'
+;; and `display-warnings'.
+
+;;; Code:
+
+(defvar warning-levels
+  '((:emergency "Emergency: " ding)
+    (:error "Error: ")
+    (:warning "Warning: ")
+    (:debug "Debug: "))
+  "List of severity level definitions for `define-warnings'.
+Each element looks like (LEVEL STRING FUNCTION) and
+defines LEVEL as a severity level.  STRING is the description
+to use in the buffer, and FUNCTION (which may be omitted)
+if non-nil is a function to call with no arguments
+to get the user's attention.
+
+:debug level is ignored by default (see `warning-minimum-level').")
+(put 'warning-levels 'risky-local-variable t)
+
+;; These are for compatibility with XEmacs.
+;; I don't think there is any chance of finding meaningful distinctions
+;; to distinguish so many levels.
+(defvar warning-level-aliases
+  '((emergency . :emergency)
+    (error . :error)
+    (warning . :warning)
+    (notice . :warning)
+    (info . :warning)
+    (critical . :emergency)
+    (alarm . :emergency))
+  "Alist of aliases for severity levels for `display-warning'.
+Each element looks like (ALIAS . LEVEL) and defines
+ALIAS as equivalent to LEVEL.")
+
+(defcustom warning-minimum-level :warning
+  "Minimum severity level for displaying the warning buffer.
+If a warning's severity level is lower than this,
+the warning is logged in the warnings buffer, but the buffer
+is not immediately displayed.  See also `warning-minimum-log-level'."
+  :group 'warnings
+  :type '(choice (const :emergency) (const :error) (const :warning))
+  :version "21.4")
+(defvaralias 'display-warning-minimum-level 'warning-minimum-level)
+
+(defcustom warning-minimum-log-level :warning
+  "Minimum severity level for logging a warning.
+If a warning severity level is lower than this,
+the warning is completely ignored."
+  :group 'warnings
+  :type '(choice (const :emergency) (const :error) (const :warning))
+  :version "21.4")
+(defvaralias 'log-warning-minimum-level 'warning-minimum-log-level)
+
+(defcustom warning-suppress-log nil
+  "List of warning types that should not be logged.
+If any element of this list matches the GROUP argument to `display-warning',
+the warning is completely ignored.
+The element must match the first elements of GROUP.
+Thus, (foo bar) as an element matches (foo bar)
+or (foo bar ANYTHING...) as GROUP.
+If GROUP is a symbol FOO, that is equivalent to the list (FOO)
+so only the element (FOO) will match it."
+  :group 'warnings
+  :type '(repeat (repeat symbol))
+  :version "21.4")
+
+(defcustom warning-suppress nil
+  "Custom groups for warnings not to display immediately.
+If any element of this list matches the GROUP argument to `display-warning',
+the warning is logged nonetheless, but the warnings buffer is
+not immediately displayed.
+The element must match an initial segment of the list GROUP.
+Thus, (foo bar) as an element matches (foo bar)
+or (foo bar ANYTHING...) as GROUP.
+If GROUP is a symbol FOO, that is equivalent to the list (FOO),
+so only the element (FOO) will match it.
+See also `warning-suppress-log'."
+  :group 'warnings
+  :type '(repeat (repeat symbol))
+  :version "21.4")
+
+(defvar warning-prefix-function nil
+  "Function to generate warning prefixes.
+This function, if non-nil, is called with two arguments,
+the severity level and its entry in `warning-levels',
+and should return the entry that should actually be used.
+The warnings buffer is current when this function is called
+and the function can insert text in it.  This text becomes
+the beginning of the warning.")
+
+(defun warning-numeric-level (level)
+  "Return a numeric measure of the warning severity level LEVEL."
+  (let* ((elt (assq level warning-levels))
+         (link (memq elt warning-levels)))
+    (length link)))
+  
+(defvar warning-series nil
+  "Non-nil means treat multiple `display-warning' calls as a series.
+An integer is a position in the warnings buffer
+which is the start of the current series.
+t means the next warning begins a series (and stores an integer here).
+A symbol with a function definition is like t, except
+also call that function before the next warning.")
+(put 'warning-series 'risky-local-variable t)
+
+(defvar warning-fill-prefix nil
+  "Non-nil means fill each warning text using this string as `fill-prefix'.")
+
+(defun warning-suppress-p (group suppress-list)
+  "Non-nil if a warning with group GROUP should be suppressed.
+SUPPRESS-LIST is the list of kinds of warnings to suppress."
+  (let (some-match)
+    (dolist (elt suppress-list)
+      (if (symbolp group)
+          ;; If GROUP is a symbol, the ELT must be (GROUP).
+          (if (and (consp elt)
+                   (eq (car elt) group)
+                   (null (cdr elt)))
+              (setq some-match t))
+        ;; If GROUP is a list, ELT must match it or some initial segment of it.
+        (let ((tem1 group)
+              (tem2 elt)
+              (match t))
+          ;; Check elements of ELT until we run out of them.
+          (while tem2
+            (if (not (equal (car tem1) (car tem2)))
+                (setq match nil))
+            (setq tem1 (cdr tem1)
+                  tem2 (cdr tem2)))
+          ;; If ELT is an initial segment of GROUP, MATCH is t now.
+          ;; So set SOME-MATCH.
+          (if match
+              (setq some-match t)))))
+    ;; If some element of SUPPRESS-LIST matched,
+    ;; we return t.
+    some-match))
+
+(defun display-warning (group message &optional level buffer-name)
+  "Display a warning message, MESSAGE.
+GROUP should be a custom group name (a symbol).
+or else a list of symbols whose first element is a custom group name.
+\(The rest of the symbols represent subcategories, for warning purposes
+only, and you can use whatever symbols you like.)
+
+LEVEL should be either :warning, :error, or :emergency.
+:emergency -- a problem that will seriously impair Emacs operation soon
+              if you do not attend to it promptly.
+:error     -- data or circumstances that are inherently wrong.
+:warning   -- data or circumstances that are not inherently wrong,
+              but raise suspicion of a possible problem.
+:debug     -- info for debugging only.
+
+BUFFER-NAME, if specified, is the name of the buffer for logging the
+warning.  By default, it is `*Warnings*'.
+
+See the `warnings' custom group for user customization features.
+
+See also `warning-series', `warning-prefix-function' and
+`warning-fill-prefix' for additional programming features."
+  (unless level
+    (setq level :warning))
+  (if (assq level warning-level-aliases)
+      (setq level (cdr (assq level warning-level-aliases))))
+  (or (< (warning-numeric-level level)
+         (warning-numeric-level warning-minimum-log-level))
+      (warning-suppress-p group warning-suppress-log)
+      (let* ((groupname (if (consp group) (car group) group))
+             (buffer (get-buffer-create (or buffer-name "*Warnings*")))
+             (level-info (assq level warning-levels))
+             start end)
+        (with-current-buffer buffer
+          (goto-char (point-max))
+          (when (and warning-series (symbolp warning-series))
+            (setq warning-series
+                  (prog1 (point)
+                    (unless (eq warning-series t)
+                      (funcall warning-series)))))
+          (unless (bolp)
+            (newline))
+          (setq start (point))
+          (if warning-prefix-function
+              (setq level-info (funcall warning-prefix-function
+                                        level level-info)))
+          (insert (nth 1 level-info) message)
+          (newline)
+          (when (and warning-fill-prefix (not (string-match "\n" message)))
+            (let ((fill-prefix warning-fill-prefix)
+                  (fill-column 78))
+              (fill-region start (point))))
+          (setq end (point))
+          (when warning-series
+            (goto-char warning-series)))
+        (if (nth 2 level-info)
+            (funcall (nth 2 level-info)))
+        (if noninteractive
+            ;; Noninteractively, take the text we inserted
+            ;; in the warnings buffer and print it.
+            ;; Do this unconditionally, since there is no way
+            ;; to view logged messages unless we output them.
+            (with-current-buffer buffer
+              (message "%s" (buffer-substring start end)))
+          ;; Interactively, decide whether the warning merits
+          ;; immediate display.
+          (or (< (warning-numeric-level level)
+                 (warning-numeric-level warning-minimum-level)) 
+              (warning-suppress-p group warning-suppress)
+              (let ((window (display-buffer buffer)))
+                (when warning-series
+                  (set-window-start window warning-series))
+                (sit-for 0)))))))
+
+(defun lwarn (group level message &rest args)
+  "Display a warning message made from (format MESSAGE ARGS...).
+Aside from generating the message with `format',
+this is equivalent to `display-message'.
+
+GROUP should be a custom group name (a symbol).
+or else a list of symbols whose first element is a custom group name.
+\(The rest of the symbols represent subcategories and
+can be whatever you like.)
+
+LEVEL should be either :warning, :error, or :emergency.
+:emergency -- a problem that will seriously impair Emacs operation soon
+              if you do not attend to it promptly.
+:error     -- invalid data or circumstances.
+:warning   -- suspicious data or circumstances."
+  (display-warning group (apply 'format message args) level))
+
+(defun warn (message &rest args)
+  "Display a warning message made from (format MESSAGE ARGS...).
+Aside from generating the message with `format',
+this is equivalent to `display-message', using
+`emacs' as the group and `:warning' as the level."
+  (display-warning 'emacs (apply 'format message args)))
+
+;;; warnings.el ends here