Re: Fill column indicator functionality

[Alp Aker <alptekin.aker@gmail.com>]

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> > User customization could be accommodated by something like the below
(naive) patch.  We define
> > fill-column-indicator face to have unspecified background; when
displaying the indicator we merge the
> > indicator face into the current it->face_id (the same face used for the
stretch glyph preceding the indicator).
>
> What about the case there's no stretch, i.e. the indicator directly
> follows the last character of the line?

Apologies for my poor phrasing, but I think you might misunderstand the
intent.  I meant that we use the background that is in effect before we
draw anything related to the indicator, not that we take the face *from*
the stretch glyph.

I did miss that the indicator is also drawn in append_space_for_newline.
Revised patch below.

diff --git a/lisp/faces.el b/lisp/faces.el
index b933279064..207b627f25 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -2502,7 +2502,9 @@ line-number-current-line

 ;; Definition stolen from display-line-numbers.
 (defface fill-column-indicator
-  '((t :inherit (shadow default)))
+  '((t :inherit shadow :weight normal :slant normal
+       :underline nil :overline nil :strike-through nil
+       :box nil :invert-video nil :stipple nil))
   "Face for displaying fill column indicator.
 This face is used when `display-fill-column-indicator-mode' is
 non-nil."
diff --git a/src/xdisp.c b/src/xdisp.c
index 1782748144..61ea050b4a 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -20201,7 +20201,7 @@ append_space_for_newline (struct it *it, bool
default_face_p)
       XFIXNAT (Vdisplay_fill_column_indicator_character);
             it->face_id =
       merge_faces (it->w, Qfill_column_indicator,
-                   0, DEFAULT_FACE_ID);
+                   0, saved_face_id);
             face = FACE_FROM_ID(it->f, it->face_id);
             goto produce_glyphs;
           }
@@ -20494,7 +20494,7 @@ extend_face_to_end_of_line (struct it *it)
                  XFIXNAT (Vdisplay_fill_column_indicator_character);
                it->face_id =
                  merge_faces (it->w, Qfill_column_indicator,
-                              0, DEFAULT_FACE_ID);
+                                    0, saved_face_id);
                PRODUCE_GLYPHS (it);
              }

@@ -20658,7 +20658,7 @@ extend_face_to_end_of_line (struct it *it)
          {
    const int saved_face = it->face_id;
    it->face_id =
-     merge_faces (it->w, Qfill_column_indicator, 0, DEFAULT_FACE_ID);
+     merge_faces (it->w, Qfill_column_indicator, 0, saved_face);
    it->c = it->char_to_display =
      XFIXNAT (Vdisplay_fill_column_indicator_character);
    PRODUCE_GLYPHS (it);

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