From: Eli Zaretskii <eliz@gnu.org>
Date: Sat, 14 Nov 2020 11:43:16 +0000 (+0200)
Subject: Avoid crashes when a reversed glyph row starts with a composition
X-Git-Tag: emacs-27.1.90~60
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=daff3bda10d15fe20f5f6e9c5f5ca60b97cf80df;p=emacs.git

Avoid crashes when a reversed glyph row starts with a composition

* src/dispnew.c (build_frame_matrix_from_leaf_window): Add an
assertion to prevent us from overwriting non-char glyphs with the
vertical border glyph.
* src/xdisp.c (extend_face_to_end_of_line): Account for one glyph
possibly inserted by append_space_for_newline.  (Bug#44506)
Remove a kludgey correction for an off-by-one error in column
counting, which is no longer needed.
---

diff --git a/src/dispnew.c b/src/dispnew.c
index df55b32c718..7822829d648 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -2559,11 +2559,15 @@ build_frame_matrix_from_leaf_window (struct glyph_matrix *frame_matrix, struct w
 	     the corresponding frame row to be updated.  */
 	  frame_row->enabled_p = true;
 
-          /* Maybe insert a vertical border between horizontally adjacent
+	  /* Maybe insert a vertical border between horizontally adjacent
 	     windows.  */
-          if (GLYPH_CHAR (right_border_glyph) != 0)
+	  if (GLYPH_CHAR (right_border_glyph) != 0)
 	    {
-              struct glyph *border = window_row->glyphs[LAST_AREA] - 1;
+	      struct glyph *border = window_row->glyphs[LAST_AREA] - 1;
+	      /* It's a subtle bug if we are overwriting some non-char
+		 glyph with the vertical border glyph.  */
+	      eassert (border->type == CHAR_GLYPH);
+	      border->type = CHAR_GLYPH;
 	      SET_CHAR_GLYPH_FROM_GLYPH (*border, right_border_glyph);
 	    }
 
diff --git a/src/xdisp.c b/src/xdisp.c
index 71a5f1c34f0..681df093418 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -22074,13 +22074,14 @@ extend_face_to_end_of_line (struct it *it)
                      default_face->id : face->id);
 
       /* Display fill-column indicator if needed.  */
-      /* We need to subtract 1 to the indicator_column here because we
-	 will add the indicator IN the column indicator number, not
-	 after it.  We compare the variable it->current_x before
-	 producing the glyph.  When FRAME_WINDOW_P we subtract
-	 CHAR_WIDTH calculating STRETCH_WIDTH for the same reason.  */
-      const int indicator_column =
-	fill_column_indicator_column (it, 1) - 1;
+      const int indicator_column = fill_column_indicator_column (it, 1);
+
+      /* Make sure our idea of current_x is in sync with the glyphs
+	 actually in the glyph row.  They might differ because
+	 append_space_for_newline can insert one glyph without
+	 updating current_x.  */
+      it->current_x = it->glyph_row->used[TEXT_AREA];
+
       do
 	{
 	  if (it->current_x != indicator_column)