calc.el (calc-trail-mode,calc-refresh): Use `face' property to italicize headers.

(calc-highlight-selections-with-faces): New variable.
(calc-selected-face, calc-nonselected-face): New faces.

calccomp.el (math-comp-highlight-string): Use
`calc-highlight-selections-with-faces' to determine how to highlight
subformulas.

calc-sel.el (calc-show-selections): Change message to something
appropriate. 

calc.texi (Making Selections, Selecting Subformulas)
(Customizing Calc): Mention how to use faces to emphasize selected
subformulas.

4 files changed, 54 insertions, 11 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index e457317c84a..701a9cc52c8 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,17 @@
+2010-08-08  Jay Belanger  <jay.p.belanger@gmail.com>
+
+	* calc/calc.el (calc-trail-mode,calc-refresh): Use `face' property
+	to italicize headers.
+	(calc-highlight-selections-with-faces): New variable.
+	(calc-selected-face, calc-nonselected-face): New faces.
+
+	* calc/calccomp.el (math-comp-highlight-string): Use
+	`calc-highlight-selections-with-faces' to determine how to highlight
+	sub-formulas.
+
+	* calc/calc-sel.el (calc-show-selections): Change message to when
+	using faces to highlight selections.
+
 2010-08-07  Michael R. Mauger  <mmaug@yahoo.com>
 
 	* progmodes/sql.el (sql-mode-sqlite-font-lock-keywords): Added
diff --git a/lisp/calc/calc-sel.el b/lisp/calc/calc-sel.el
index 084b9ea2b6a..c485fdd168a 100644
--- a/lisp/calc/calc-sel.el
+++ b/lisp/calc/calc-sel.el
@@ -309,6 +309,8 @@
        (setq n (1+ n))))
    (calc-clear-command-flag 'position-point)))
 
+(defvar calc-highlight-selections-with-faces)
+
 (defun calc-show-selections (arg)
   (interactive "P")
   (calc-wrapper
@@ -330,8 +332,12 @@
 		(setcar (nthcdr 2 calc-selection-cache-entry) nil)
 		(calc-change-current-selection sel)))))
    (message (if calc-show-selections
-		"Displaying only selected part of formulas"
-	      "Displaying all but selected part of formulas"))))
+                (if calc-highlight-selections-with-faces
+                    "De-emphasizing all but selected part of formulas"
+                  "Displaying only selected part of formulas")
+              (if calc-highlight-selections-with-faces
+                  "Emphasizing selected part of formulas"
+                "Displaying all but selected part of formulas")))))
 
 ;; The variables calc-final-point-line and calc-final-point-column
 ;; are declared in calc.el, and are used throughout.
diff --git a/lisp/calc/calc.el b/lisp/calc/calc.el
index 7ea371dd16e..e0560465a99 100644
--- a/lisp/calc/calc.el
+++ b/lisp/calc/calc.el
@@ -425,6 +425,27 @@ in normal mode."
   :group 'calc
   :type 'integer)
 
+(defcustom calc-highlight-selections-with-faces
+  nil
+  "If non-nil, use a separate face to indicate selected sub-formulas.
+If `calc-show-selections' is non-nil, then selected sub-formulas are shown
+by displaying the rest of the formula in `calc-nonselected-face'.  
+If `calc-show-selections' is nil, then selected sub-formulas are shown
+by displaying the sub-formula in `calc-selected-face'."
+  :group 'calc
+  :type 'boolean)
+
+(defface calc-nonselected-face
+  '((t :inherit shadow       
+       :slant italic))
+  "Face used to show the non-selected portion of a formula."
+  :group 'calc)
+
+(defface calc-selected-face
+  '((t :weight bold))
+  "Face used to show the selected portion of a formula."
+  :group 'calc)
+
 (defvar calc-bug-address "jay.p.belanger@gmail.com"
   "Address of the maintainer of Calc, for use by `report-calc-bug'.")
 
@@ -1385,8 +1406,7 @@ commands given here will actually operate on the *Calculator* stack."
     (set (make-local-variable 'calc-main-buffer) buf))
   (when (= (buffer-size) 0)
     (let ((buffer-read-only nil))
-      (insert (propertize (concat "Emacs Calculator Trail\n")
-			  'font-lock-face 'italic))))
+      (insert (propertize "Emacs Calculator Trail\n" 'face 'italic))))
   (run-mode-hooks 'calc-trail-mode-hook))
 
 (defun calc-create-buffer ()
@@ -1976,7 +1996,7 @@ See calc-keypad for details."
 	 (erase-buffer)
 	 (when calc-show-banner
 	   (insert (propertize "--- Emacs Calculator Mode ---\n"
-			       'font-lock-face 'italic)))
+			       'face 'italic)))
 	 (while thing
 	   (goto-char (point-min))
 	   (when calc-show-banner
diff --git a/lisp/calc/calccomp.el b/lisp/calc/calccomp.el
index 7aeb31c7719..6923cd7693a 100644
--- a/lisp/calc/calccomp.el
+++ b/lisp/calc/calccomp.el
@@ -1339,12 +1339,15 @@
 
 (defun math-comp-highlight-string (s)
   (setq s (copy-sequence s))
-  (let ((i (length s)))
-    (while (>= (setq i (1- i)) 0)
-      (or (memq (aref s i) '(32 ?\n))
-	  (aset s i (if calc-show-selections ?\. ?\#)))))
-  s)
-
+  (if calc-highlight-selections-with-faces
+      (if (not calc-show-selections)
+          (propertize s 'face 'calc-selected-face)
+        (propertize s 'face 'calc-nonselected-face))
+    (let ((i (length s)))
+      (while (>= (setq i (1- i)) 0)
+        (or (memq (aref s i) '(32 ?\n))
+            (aset s i (if calc-show-selections ?\. ?\#)))))
+    s))
 
 ;; The variable math-comp-sel-tag is local to calc-find-selected-part
 ;; in calc-sel.el, but is used by math-comp-sel-flat-term and