bug#69942: 30.0.50; Fontification of radio-button widget labels

[Stephen Berman via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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On Sun, 21 Apr 2024 21:45:21 +0200 Stephen Berman <stephen.berman@gmx.net> wrote:

> On Thu, 18 Apr 2024 15:37:58 +0200 Stephen Berman <stephen.berman@gmx.net> wrote:
>
>> On Thu, 18 Apr 2024 07:07:43 -0300 Mauro Aranda <maurooaranda@gmail.com> wrote:
>>
>>> Eli Zaretskii <eliz@gnu.org> writes:
>>>
>>>>> Date: Mon, 8 Apr 2024 07:58:44 -0300
>>>>> Cc: 69942@debbugs.gnu.org
>>>>> From: Mauro Aranda <maurooaranda@gmail.com>
>>>>>
>>>>> On 6/4/24 06:02, Eli Zaretskii wrote:
>>>>>  >> From: Stephen Berman <stephen.berman@gmx.net>
>>>>>  >> Cc: Eli Zaretskii <eliz@gnu.org>, 69942@debbugs.gnu.org
>>>>>  >> Date: Mon, 01 Apr 2024 17:21:27 +0200
>>>>>  >>
>>>>>  >> On Mon, 25 Mar 2024 01:40:36 +0100 Stephen Berman
>>>>> <stephen.berman@gmx.net> wrote:
>>>>>  >>
>>>>>  >>> Ok, I've gotten further with implementing disinguishing by faces
>>>>>  >>> selected (chosen) and unselected radio buttons in radio-button-choice
>>>>>  >>> widgets and check boxes in checklist widgets, see the attached patch.
>>>>>  >>> Initial tests seem ok, but it definitely needs more testing.
>>>>>  >>
>>>>>  >> Any comments on this patch for using a widget-unselected face?  I have
>>>>>  >> been detained from further testing this past week, but can now resume.
>>>>>  >
>>>>>  > Mauro, any further comments?
>>>>>
>>>>> Hi Eli and Stephen,
>>>>>
>>>>> Please forgive me, for the past 2 weeks I haven't been able to do any
>>>>> computer stuff.  If it's OK, please give me until the weekend so I
>>>>> can catch up with this and the other 2 bug reports by Stephen.
>>>>
>>>> Mauro, were you able to find time to look into this and the other 2
>>>> bugs?
>>>
>>> I have, just now.  The patch looks good to me.  It'll be great if
>>> Stephen can add some documentation to the manual, so it stays updated.
>>> If not, I can do that in a few days.
>>
>> Sure, I'll add documentation and post it here for approval before
>> pushing the changes.
>
> I've encountered some problems with the patch.  One is that it breaks
> the display of all face attributes in the customize-face buffer.  I've
> determined the part of the patch that triggers this, though I haven't
> yet figured out just why this bit of code breaks the display.  Also, it
> appears that the widget-unselected face does not completely replace
> widget-inactive where it's intended to do so, but I need to do more
> testing and debugging here to find out why.  Until I've fixed these
> issues the patch is not suitable for installing, so I'm also holding off
> with the accompanying documentation.  (But in preparation for the
> documentation I looked more closely at the Widget manual and found
> several typos and other issues, for which I opened bug#70502.)

The breakage in displaying all face attributes in the customize-face
buffer was caused by the invocation of `(widget-specify-selected child)'
in widget-checklist-add-item in the cond-clause satisfying
`(widget-inline-p type t)'.  I still don't understand why it has this
effect, and I have to admit that I don't understand what an inline
widget is.  But simply omitting the invocation of
`(widget-specify-selected child)' at this point in the patch does avoid
the customize-face breakage and I have not noticed any problems due to
this omission.

As for the problematic interaction between the widget-unselected and
widget-inactive faces, this seems to have been due to my having copied
most of the definition of widget-specify-unselected from that of
widget-specify-inactive, and specifically, copying the overlay priority.
In the attached patch, widget-specify-unselected now uses a lower
overlay priority than the one used in widget-specify-inactive, and in my
tests this yields the desired results: the labels of active checkboxes
and radio-buttons have widget-unselected face but when these widgets are
deactivated, the labels have widget-inactive face.

Another change I've made in the attached patch is to have the default
value of widget-unselected face inherit from widget-inactive instead of
inheriting from shadow face, like widget-inactive does by default.  This
way, if a user customizes widget-inactive, that will also apply by
default to widget-unselected, thus retaining the current default widget
UI where the labels of checkboxes and radio-buttons have widget-inactive
face.  (Thus, the "desired results" in the preceding paragraph are only
visible when widget-unselected face is customized to differ from
widget-unselected face.)

Finally, regarding documentation of widget-unselected face in the Widget
manual, I think it would be helpful for the documentation to mention the
use case that motivated introducing it (following Mauro's suggestion to
use a face instead of a defcustom), namely, to visually distinguish the
labels of unselected and inactive widgets.  Here is what I suggest:

@deffn Face widget-unselected
Face used for unselected widgets.  This face is also used on the text
labels of radio-button and checkbox widgets.

The default value inherits @code{widget-inactive} face.  If you want to
visually distinguish the labels of unselected active radio-button or
checkbox widgets from the labels of unselected inactive widgets,
customize this face to a non-default value.
@end deffn

Since the recent widget.texi changes that include documenting
widget-inactive face have not yet been merged to master, I haven't
included the propopsed documentaton of widget-unselected in the attached
patch, but if approved, will of course add it after the merge.

Steve Berman


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diff --git a/lisp/wid-edit.el b/lisp/wid-edit.el
index dc481d4d0a5..b7673b01c73 100644
--- a/lisp/wid-edit.el
+++ b/lisp/wid-edit.el
@@ -555,6 +555,29 @@ widget-specify-active
       (delete-overlay inactive)
       (widget-put widget :inactive nil))))

+(defface widget-unselected
+  '((t :inherit widget-inactive))
+  "Face used for unselected widgets."
+  :group 'widget-faces
+  :version "30.1")
+
+(defun widget-specify-unselected (widget from to)
+  "Fontify WIDGET as unselected (not chosen)."
+  (let ((overlay (make-overlay from to nil t nil)))
+    (overlay-put overlay 'face 'widget-unselected)
+    (overlay-put overlay 'evaporate t)
+    ;; The overlay priority here should be lower than the priority in
+    ;; `widget-specify-active' (bug#69942).
+    (overlay-put overlay 'priority 90)
+    (widget-put widget :unselected overlay)))
+
+(defun widget-specify-selected (widget)
+  "Remove fontification of WIDGET as unselected (not chosen)."
+  (let ((unselected (widget-get widget :unselected)))
+    (when unselected
+      (delete-overlay unselected)
+      (widget-put widget :unselected nil))))
+
 ;;; Widget Properties.

 (defsubst widget-type (widget)
@@ -2439,10 +2462,16 @@ 'checkbox
 (defun widget-checkbox-action (widget &optional event)
   "Toggle checkbox, notify parent, and set active state of sibling."
   (widget-toggle-action widget event)
-  (let ((sibling (widget-get-sibling widget)))
+  (let* ((sibling (widget-get-sibling widget))
+         (from (widget-get sibling :from))
+	 (to (widget-get sibling :to)))
     (when sibling
-      (widget-apply sibling
-	            (if (widget-value widget) :activate :deactivate))
+      (if (widget-value widget)
+          (progn
+            (widget-apply sibling :activate)
+            (widget-specify-selected sibling))
+        :deactivate
+        (widget-specify-unselected sibling from to))
       (widget-clear-undo))))

 ;;; The `checklist' Widget.
@@ -2498,15 +2527,18 @@ widget-checklist-add-item
 	       ((eq escape ?v)
 		(setq child
 		      (cond ((not chosen)
-			     (let ((child (widget-create-child widget type)))
-			       (widget-apply child :deactivate)
+			     (let* ((child (widget-create-child widget type))
+                                    (from (widget-get child :from))
+			            (to (widget-get child :to)))
+                               (widget-specify-unselected child from to)
 			       child))
                             ((widget-inline-p type t)
 			     (widget-create-child-value
 			      widget type (cdr chosen)))
 			    (t
 			     (widget-create-child-value
-			      widget type (car (cdr chosen)))))))
+			      widget type (car (cdr chosen)))
+                             (widget-specify-selected child)))))
 	       (t
 		(error "Unknown escape `%c'" escape)))))
      ;; Update properties.
@@ -2677,8 +2709,11 @@ widget-radio-add-item
 				(widget-create-child-value
 				 widget type value)
 			      (widget-create-child widget type)))
-		(unless chosen
-		  (widget-apply child :deactivate)))
+                (if chosen
+                    (widget-specify-selected child)
+                  (let ((from (widget-get child :from))
+			(to (widget-get child :to)))
+                    (widget-specify-unselected child from to))))
 	       (t
 		(error "Unknown escape `%c'" escape)))))
      ;; Update properties.
@@ -2728,14 +2763,17 @@ widget-radio-value-set
     (dolist (current (widget-get widget :children))
       (let* ((button (widget-get current :button))
 	     (match (and (not found)
-			 (widget-apply current :match value))))
+			 (widget-apply current :match value)))
+             (from (widget-get current :from))
+	     (to (widget-get current :to)))
 	(widget-value-set button match)
 	(if match
-	    (progn
-	      (widget-value-set current value)
-	      (widget-apply current :activate))
-	  (widget-apply current :deactivate))
-	(setq found (or found match))))))
+            (progn
+              (widget-value-set current value)
+              (widget-apply current :activate)
+              (widget-specify-selected current))
+          (widget-specify-unselected current from to))
+        (setq found (or found match))))))

 (defun widget-radio-validate (widget)
   ;; Valid if we have made a valid choice.
@@ -2755,13 +2793,16 @@ widget-radio-action
   (let ((buttons (widget-get widget :buttons)))
     (when (memq child buttons)
       (dolist (current (widget-get widget :children))
-	(let* ((button (widget-get current :button)))
+	(let* ((button (widget-get current :button))
+               (from (widget-get current :from))
+	       (to (widget-get current :to)))
 	  (cond ((eq child button)
 		 (widget-value-set button t)
-		 (widget-apply current :activate))
+		 (widget-apply current :activate)
+                 (widget-specify-selected current))
 		((widget-value button)
 		 (widget-value-set button nil)
-		 (widget-apply current :deactivate)))))))
+                 (widget-specify-unselected current from to)))))))
   ;; Pass notification to parent.
   (widget-apply widget :notify child event))