bug#54970: 28.1; Some emoji no longer display

[Alan Third <alan@idiocy.org>]

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On Sun, Apr 17, 2022 at 08:47:07PM +0100, Alan Third wrote:
> On Sun, Apr 17, 2022 at 08:27:45PM +0100, Alan Third wrote:
> > On Sun, Apr 17, 2022 at 09:58:56PM +0300, Eli Zaretskii wrote:
> > > No idea.  Maybe it's a macOS thing or something?
> > 
> > I'm pretty sure that I've never ever seen NS Emacs on macOS produce
> > anything but a blank square (and it's always a square) for missing
> > characters.
> 
> Hmm, in fact, is this, from nsterm.m, the culprit?
> 
>     case GLYPHLESS_GLYPH:
>       if (s->for_overlaps || (s->cmp_from > 0
> 			      && ! s->first_glyph->u.cmp.automatic))
>         s->background_filled_p = 1;
>       else
>         ns_maybe_dumpglyphs_background
>           (s, s->first_glyph->type == COMPOSITE_GLYPH);
>       /* ... */
>       /* Not yet implemented.  */
>       /* ... */
>       break;

To answer my own question: yes. Yes it is.

Patch attached.

It doesn't look to me like it displays quite right, the right hand
side of the hex code gets cut off on my Mac and under GNUstep only the
first line is displayed, but I can't see any reason for it.

Maybe this is better than nothing, though.

-- 
Alan Third

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From a3f75f63fed67e4a63eb1412d910c9e66c4cc2b8 Mon Sep 17 00:00:00 2001
From: Alan Third <alan@idiocy.org>
Date: Sun, 17 Apr 2022 21:15:05 +0100
Subject: [PATCH] Fix glyphless glyph display on NS (bug#54970)

* src/nsterm.m (ns_draw_glyphless_glyph_string_foreground): New
function.
(ns_draw_glyph_string): Use the new function.
---
 src/nsterm.m | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 76 insertions(+), 3 deletions(-)

diff --git a/src/nsterm.m b/src/nsterm.m
index 550f29212e..18e219949b 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -3945,6 +3945,81 @@ Function modeled after x_draw_glyph_string_box ().
     }
 }
 
+/* Draw the foreground of glyph string S for glyphless characters.  */
+static void
+ns_draw_glyphless_glyph_string_foreground (struct glyph_string *s)
+{
+  struct glyph *glyph = s->first_glyph;
+  unsigned char2b[8];
+  int x, i, j;
+
+  /* If first glyph of S has a left box line, start drawing the text
+     of S to the right of that box line.  */
+  if (s->face && s->face->box != FACE_NO_BOX
+      && s->first_glyph->left_box_line_p)
+    x = s->x + max (s->face->box_vertical_line_width, 0);
+  else
+    x = s->x;
+
+  s->char2b = char2b;
+
+  for (i = 0; i < s->nchars; i++, glyph++)
+    {
+      char buf[7];
+      char *str = NULL;
+      int len = glyph->u.glyphless.len;
+
+      if (glyph->u.glyphless.method == GLYPHLESS_DISPLAY_ACRONYM)
+	{
+	  if (len > 0
+	      && CHAR_TABLE_P (Vglyphless_char_display)
+	      && (CHAR_TABLE_EXTRA_SLOTS (XCHAR_TABLE (Vglyphless_char_display))
+		  >= 1))
+	    {
+	      Lisp_Object acronym
+		= (! glyph->u.glyphless.for_no_font
+		   ? CHAR_TABLE_REF (Vglyphless_char_display,
+				     glyph->u.glyphless.ch)
+		   : XCHAR_TABLE (Vglyphless_char_display)->extras[0]);
+	      if (STRINGP (acronym))
+		str = SSDATA (acronym);
+	    }
+	}
+      else if (glyph->u.glyphless.method == GLYPHLESS_DISPLAY_HEX_CODE)
+	{
+	  unsigned int ch = glyph->u.glyphless.ch;
+	  eassume (ch <= MAX_CHAR);
+	  sprintf (buf, "%0*X", ch < 0x10000 ? 4 : 6, ch);
+	  str = buf;
+	}
+
+      if (str)
+	{
+	  int upper_len = (len + 1) / 2;
+
+	  /* It is assured that all LEN characters in STR is ASCII.  */
+	  for (j = 0; j < len; j++)
+            char2b[j] = s->font->driver->encode_char (s->font, str[j]) & 0xFFFF;
+	  s->font->driver->draw (s, 0, upper_len,
+				 x + glyph->slice.glyphless.upper_xoff,
+				 s->ybase + glyph->slice.glyphless.upper_yoff,
+				 false);
+	  s->font->driver->draw (s, upper_len, len,
+				 x + glyph->slice.glyphless.lower_xoff,
+				 s->ybase + glyph->slice.glyphless.lower_yoff,
+				 false);
+	}
+      if (glyph->u.glyphless.method != GLYPHLESS_DISPLAY_THIN_SPACE)
+        ns_draw_box (NSMakeRect (x, s->ybase - glyph->ascent,
+                                 glyph->pixel_width - 1,
+                                 glyph->ascent + glyph->descent - 1),
+                     1, 1,
+                     [NSColor colorWithUnsignedLong:NS_FACE_FOREGROUND (s->face)],
+                     YES, YES);
+      x += glyph->pixel_width;
+   }
+}
+
 static void
 ns_draw_glyph_string (struct glyph_string *s)
 /* --------------------------------------------------------------------------
@@ -4058,9 +4133,7 @@ Function modeled after x_draw_glyph_string_box ().
       else
         ns_maybe_dumpglyphs_background
           (s, s->first_glyph->type == COMPOSITE_GLYPH);
-      /* ... */
-      /* Not yet implemented.  */
-      /* ... */
+      ns_draw_glyphless_glyph_string_foreground (s);
       break;
 
     default:
-- 
2.35.1