[PATCH] Emacs should check font width also when spacing is dual

[PATCH] Emacs should check font width also when spacing is dual

[Naohiro Aota]

Hi,

I found that emacs check character width one by one to calculate
font->min_width, font->average_width, font->space_width only when
`spacing' is not FC_PROPORTIONAL. But fontconfig's doc (1) says
"FC_DUAL, where the font has glyphs in precisely two widths, one twice
as wide as the other". So emacs should check them one by one also when
spacing is dual. Current behavior causes tab width to be doubled and so
indent to be strange.

To solve this, I suggest a tiny patch below. 

2009-06-17  Naohiro Aota  <naota@elisp.net>

	* xftfont.c (xftfont_open): Check font width one by one also when
	spacing is dual.

	* ftfont.c (ftfont_open): Ditto.

--8<---------------cut here---------------start------------->8---
--- src/ftfont.c	17 Apr 2009 18:38:02 -0000	1.54
+++ src/ftfont.c	17 Jun 2009 14:51:37 -0000
@@ -1244,7 +1244,7 @@
     spacing = XINT (AREF (entity, FONT_SPACING_INDEX));
   else
     spacing = FC_PROPORTIONAL;
-  if (spacing != FC_PROPORTIONAL)
+  if (spacing != FC_PROPORTIONAL && spacing != FC_DUAL)
     font->min_width = font->average_width = font->space_width
       = (scalable ? ft_face->max_advance_width * size / upEM
 	 : ft_face->size->metrics.max_advance >> 6);
--- src/xftfont.c	11 May 2009 09:29:49 -0000	1.24
+++ src/xftfont.c	17 Jun 2009 14:51:37 -0000
@@ -333,7 +333,7 @@
 	ascii_printable[i] = ' ' + i;
     }
   BLOCK_INPUT;
-  if (spacing != FC_PROPORTIONAL)
+  if (spacing != FC_PROPORTIONAL && spacing != FC_DUAL)
     {
       font->min_width = font->average_width = font->space_width
 	= xftfont->max_advance_width;
--8<---------------cut here---------------end--------------->8---

(1) http://fontconfig.org/fontconfig-devel/r1283.html

Regards,

Re: [PATCH] Emacs should check font width also when spacing is dual

[Chong Yidong]

Naohiro Aota <naota@elisp.net> writes:

> Current behavior causes tab width to be doubled and so indent to be
> strange.

I don't see any strange behavior.  (Tabs are displayed specially in
Emacs, so I don't know how you're viewing them.)  Please provide a
reproducible test case.

Re: [PATCH] Emacs should check font width also when spacing is dual

[Naohiro Aota]

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Chong Yidong <cyd@stupidchicken.com> writes:

> Naohiro Aota <naota@elisp.net> writes:
>
>> Current behavior causes tab width to be doubled and so indent to be
>> strange.
>
> I don't see any strange behavior.  (Tabs are displayed specially in
> Emacs, so I don't know how you're viewing them.)  Please provide a
> reproducible test case.

Using fonts whose spacing is DUAL cause the problem.  M+ font is one of
them. (1)

--8<---------------cut here---------------start------------->8---
12345678901234567890
	<-tab
(add-hook 'after-save-hook
	  (function (lambda ()
		      (if (string= (expand-file-name "~/.emacs.el")
				   (buffer-file-name))
			  (save-excursion
			    (byte-compile-file "~/.emacs.el"))))))
--8<---------------cut here---------------end--------------->8---

(unpatched) emacs -q -fn "M+ 1m", open <above file>


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same file with firefox


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same file with patched emacs


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(1) http://mplus-fonts.sourceforge.jp/mplus-outline-fonts/index-en.html