Fix and document display of glyphless characters.

 src/xdisp.c (set_cursor_from_row): Fix cursor positioning on
 zero-width characters.
 (syms_of_xdisp) <glyphless-char-display>: Doc fix.
 src/.gdbinit (pgx): Adapt to latest changes in `struct glyph'.
 src/w32term.c (x_draw_glyphless_glyph_string_foreground): Draw the
 box before drawing the glyphs inside it.
 src/dispextern.h (enum glyphless_display_method): Rename
 GLYPHLESS_DISPLAY_HEXA_CODE to GLYPHLESS_DISPLAY_HEX_CODE.  All
 users changed.
 src/term.c (append_glyphless_glyph, produce_glyphless_glyph): Fix
 comments.
 (produce_glyphless_glyph): Enclose "U+nnnn" and "empty box"
 whitespace in "[]", to simulate a box.  Don't use uninitialized
 variable `width'.
 lisp/international/characters.el (glyphless-char-display-control):
 Renamed from glyphless-char-control; all users changed.  Doc fix.
 Signal an error if display method is not one of the recognized
 symbols.
 doc/emacs/rmail.texi (Rmail Coding): Characters with no fonts are not
 necessarily displayed as empty boxes.
 doc/emacs/mule.texi (Language Environments, Fontsets): Characters with no
 fonts are not necessarily displayed as empty boxes.
 doc/emacs/display.texi (Text Display): Document display of glyphless
 characters.
 doc/lispref/display.texi (Usual Display): Characters with no fonts are not
 necessarily displayed as empty boxes.
 etc/NEWS: Document display of glyphless characters.

1 files changed, 10 insertions, 8 deletions

diff --git a/doc/emacs/mule.texi b/doc/emacs/mule.texi
index 9fdef175826..79dbf78f292 100644
--- a/doc/emacs/mule.texi
+++ b/doc/emacs/mule.texi
@@ -351,10 +351,11 @@ which prefers Cyrillic characters and files encoded in Windows-1255).
 @cindex Intlfonts package, installation
   To display the script(s) used by your language environment on a
 graphical display, you need to have a suitable font.  If some of the
-characters appear as empty boxes, you should install the GNU Intlfonts
-package, which includes fonts for most supported scripts.@footnote{If
-you run Emacs on X, you need to inform the X server about the location
-of the newly installed fonts with the following commands:
+characters appear as empty boxes or hex codes, you should install the
+GNU Intlfonts package, which includes fonts for most supported
+scripts.@footnote{If you run Emacs on X, you need to inform the X
+server about the location of the newly installed fonts with the
+following commands:
 
 @example
  xset fp+ /usr/local/share/emacs/fonts
@@ -1314,10 +1315,11 @@ characters the font does not cover.  The standard fontset is only used if
 explicitly requested, despite its name.
 
   A fontset does not necessarily specify a font for every character
-code.  If a fontset specifies no font for a certain character, or if it
-specifies a font that does not exist on your system, then it cannot
-display that character properly.  It will display that character as an
-empty box instead.
+code.  If a fontset specifies no font for a certain character, or if
+it specifies a font that does not exist on your system, then it cannot
+display that character properly.  It will display that character as a
+hex code or thin space or an empty box instead.  (@xref{Text Display,
+glyphless characters}, for details.)
 
 @node Defining Fontsets
 @section Defining fontsets