GNU bug report logs - #7887
Emacs will render some fonts under Mac OS X one pixel too tall (patch supplied)

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 7887 in the body.
You can then email your comments to 7887 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Anders Lindgren <andlind <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Emacs will render some fonts under Mac OS X one pixel too tall (patch
	supplied)
Date: Sat, 22 Jan 2011 10:43:39 +0100

Hi!

I have notices that Emacs will render some fonts under Mac OS X one
pixel too tall.

The current implementation for handling fonts under NextStep always
round the descender to the next full integer, to avoid clipping. (As
descenders under NextStep are negative, this is done using the
function "floor"). Unfortunately, some fonts do not specify the
descender as exactly as desired. Concretely, a 6x8 bitmap font could
report a descender of -2.0000040531158447 (represented by
0xc000000220000000), which Emacs rounds to -3. The result is that the
font will be drawn one pixel taller than expected.

The patch below is one example of how to handle this, it will
circumvent the problem by adding a small value to the descender,
making sure that values close enough to an integer will be rounded to
that integer.

    -- Anders Lindgren

2011-01-22  Anders Lindgren  <andlind <at> gmail.com>

	* nsfont.m (nsfont_open): Ensure that fonts with inexact
	descenders would not become one pixel too tall.


=== modified file 'src/nsfont.m'
--- src/nsfont.m	2011-01-19 22:11:33 +0000
+++ src/nsfont.m	2011-01-22 09:03:56 +0000
@@ -809,6 +809,15 @@
     const char *fontName = [[nsfont fontName] UTF8String];
     int len = strlen (fontName);

+    /* The values specified by fonts are not always exact. For
+     * example, a 6x8 font could specify that the descender is
+     * -2.00000405... (represented by 0xc000000220000000).  Without
+     * adjustment, the code below would round the descender to -3,
+     * resulting in a font that would be one pixel higher than
+     * intended. */
+
+    CGFloat adjusted_descender = [sfont descender] + 0.0001;
+
 #ifdef NS_IMPL_GNUSTEP
     font_info->nsfont = sfont;
 #else
@@ -830,7 +839,7 @@

     brect =  [sfont boundingRectForFont];
     full_height = brect.size.height;
-    min_height = [sfont ascender] - [sfont descender];
+    min_height = [sfont ascender] - adjusted_descender;
     hd = full_height - min_height;

     /* standard height, similar to Carbon. Emacs.app: was 0.5 by default. */
@@ -845,10 +854,10 @@
     /* max bounds */
     font_info->max_bounds.ascent =
       lrint (hshrink * [sfont ascender] + expand * hd/2);
-    /* [sfont descender] is usually negative.  Use floor to avoid
-       clipping descenders. */
+    /* Descender is usually negative.  Use floor to avoid clipping
+       descenders. */
     font_info->max_bounds.descent =
-      -lrint (floor(hshrink* [sfont descender] - expand*hd/2));
+      -lrint (floor(hshrink * adjusted_descender - expand * hd/2));
     font_info->height =
       font_info->max_bounds.ascent + font_info->max_bounds.descent;
     font_info->max_bounds.width = lrint (font_info->width);
@@ -884,7 +893,7 @@

     /* set up metrics portion of font struct */
     font->ascent = lrint([sfont ascender]);
-    font->descent = -lrint(floor([sfont descender]));
+    font->descent = -lrint(floor(adjusted_descender));
     font->min_width = ns_char_width(sfont, '|');
     font->space_width = lrint (ns_char_width (sfont, ' '));
     font->average_width = lrint (font_info->width);




In GNU Emacs 24.0.50.1 (x86_64-apple-darwin10.5.0, NS apple-appkit-1038.35)
 of 2011-01-14 on macpro.local
Windowing system distributor `Apple', version 10.3.1038
configured using `configure  '--with-ns''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  value of $XMODIFIERS: nil
  locale-coding-system: nil
  default enable-multibyte-characters: t

Major mode: ObjC/lw

Minor modes in effect:
  diff-auto-refine-mode: t
  subword-mode: t
  global-auto-revert-mode: t
  global-cwarn-mode: t
  minibuffer-electric-file-mode: t
  recentf-mode: t
  msb-mode: t
  display-time-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Recent input:
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <down> <down> C-SPC <down> C-w <down> C-SPC
<down> <down> <down> C-w <up> C-e <left> <left> <left>
<M-backspace> <backspace> <backspace> <backspace> C-a
C-x C-s C-M-a C-s e p s C-a C-x C-f s a <backspace>
l a s j . <backspace> <backspace> k . c <return> <C-tab>
C-x o <C-S-tab> C-x p C-M-a <up> <up> <up> <up> <up>
<up> <up> <up> <up> C-SPC <down> <down> <down> <down>
<down> <down> <down> C-w C-x C-s C-x o C-y C-x p <down>
C-v C-l C-v <down> <down-mouse-1> <mouse-1> C-a C-SPC
<down> <down> <down> <down> <down> <down> <down> C-w
C-x C-s C-x o C-y C-x C-s C-x p <down-mouse-1> <mouse-1>
M-d M-d M-d c o u l y <backspace> d SPC <backspace>
M-f <backspace> <backspace> <backspace> y <escape>
q <M-left> <M-left> <M-backspace> <escape> q <down>
<down> M-f M-f M-f <M-backspace> t h e SPC d e s c
M-- <escape> q C-x C-s <down-mouse-1> <mouse-1> <down-mouse-1>
<mouse-1> <backspace> C-a C-x C-s <down-mouse-1> <mouse-1>
SPC <down-mouse-1> <mouse-1> SPC C-a C-x C-s <down-mouse-1>
<mouse-1> SPC <down-mouse-1> <mouse-1> SPC C-a C-x
C-s <down-mouse-1> <mouse-1> C-a <down> SPC <backspace>
<down> <down> <down> <down> <down> <up> SPC <backspace>
C-a C-x C-s <up> <up> <up> <up> M-f <right> <right>
C-s C-w C-s C-a <down-mouse-1> <mouse-1> a <backspace>
a d j u s t m e n t <escape> d <escape> q <up> <up>
<up> C-a C-SPC <down> <down> <down> <down> <down> <down>
<escape> x i s p l l <backspace> <backspace> e l l
- r e g <tab> ' <backspace> <return> q <up> C-g <up>
<down-mouse-1> <mouse-1> c <escape> q <down-mouse-1>
<mouse-1> C-d <backspace> <backspace> <backspace> i
f y C-a C-x C-s <menu-bar> <help-menu> <send-emacs
-bug-report>

Recent messages:
Wrote /Users/anders/build/emacs/trunk/src/nsfont.m
Mark saved where search started
Mark set
Starting new Ispell process [default] ...
Entering debugger...
Back to top level.
Quit
Auto-saving...done
Saving file /Users/anders/build/emacs/trunk/src/nsfont.m...
Wrote /Users/anders/build/emacs/trunk/src/nsfont.m

Load-path shadows:
~/emacs/lisp/table hides
/Applications/Emacs24.app/Contents/Resources/lisp/textmodes/table
~/emacs/lisp/ruby-mode hides
/Applications/Emacs24.app/Contents/Resources/lisp/progmodes/ruby-mode
~/emacs/src/asm-mode-new/src/asm-mode hides
/Applications/Emacs24.app/Contents/Resources/lisp/progmodes/asm-mode

Features:
(ispell smerge-mode diff-mode texinfo autoconf autoconf-mode conf-mode
shadow sort gnus-util mail-extr message rfc822 mml mml-sec mm-decode
mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mailabbrev mail-utils gmm-utils mailheader emacsbug
subword newcomment ctypes grep compile etags jka-compr find-func follow
my-end-of-buffer-log c-electric-operator c-indent-operator dired-aux
dired vc-bzr sha1 hex-util add-log vc-dispatcher vc-svn pp apropos
multi-isearch debug dabbrev help-mode eldoc ps-print ps-def lpr
autorevert folding-isearch folding view rdebug cwarn prepaint cc-mode
cc-fonts cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
tempo edg-mode split-nways toggle-file-read-only lockdir uniquify
ange-ftp comint regexp-opt ring paren mic-paren iso-insert
minibuf-elfile easy-mmode recentf tree-widget wid-edit easymenu msb
edmacro kmacro warnings disp-table time advice help-fns advice-preload
cl tooltip ediff-hook vc-hooks lisp-float-type mwheel ns-win tool-bar
dnd fontset image fringe lisp-mode register page menu-bar rfn-eshadow
timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core frame cham georgian utf-8-lang misc-lang vietnamese tibetan
thai tai-viet lao korean japanese hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese case-table epa-hook
jka-cmpr-hook help simple abbrev loaddefs button minibuffer faces
cus-face files text-properties overlay md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote
make-network-process ns multi-tty emacs)

Message #8 received at 7887 <at> debbugs.gnu.org (full text, mbox):

From: "Jan D." <jan.h.d <at> swipnet.se>
To: Anders Lindgren <andlind <at> gmail.com>
Cc: 7887 <at> debbugs.gnu.org
Subject: Re: bug#7887: Emacs will render some fonts under Mac OS X one pixel
	too	tall (patch supplied)
Date: Tue, 25 Jan 2011 14:03:02 +0100

Anders Lindgren skrev 2011-01-22 10:43:
> Hi!
>
> I have notices that Emacs will render some fonts under Mac OS X one
> pixel too tall.
>
> The current implementation for handling fonts under NextStep always
> round the descender to the next full integer, to avoid clipping. (As
> descenders under NextStep are negative, this is done using the
> function "floor"). Unfortunately, some fonts do not specify the
> descender as exactly as desired. Concretely, a 6x8 bitmap font could
> report a descender of -2.0000040531158447 (represented by
> 0xc000000220000000), which Emacs rounds to -3. The result is that the
> font will be drawn one pixel taller than expected.
>
> The patch below is one example of how to handle this, it will
> circumvent the problem by adding a small value to the descender,
> making sure that values close enough to an integer will be rounded to
> that integer.

How about checking if it is negative and then use ceil instead of floor, 
and keeping floor for the positive case?

	Jan D.

>
>      -- Anders Lindgren
>
> 2011-01-22  Anders Lindgren<andlind <at> gmail.com>
>
> 	* nsfont.m (nsfont_open): Ensure that fonts with inexact
> 	descenders would not become one pixel too tall.
>
>
> === modified file 'src/nsfont.m'
> --- src/nsfont.m	2011-01-19 22:11:33 +0000
> +++ src/nsfont.m	2011-01-22 09:03:56 +0000
> @@ -809,6 +809,15 @@
>       const char *fontName = [[nsfont fontName] UTF8String];
>       int len = strlen (fontName);
>
> +    /* The values specified by fonts are not always exact. For
> +     * example, a 6x8 font could specify that the descender is
> +     * -2.00000405... (represented by 0xc000000220000000).  Without
> +     * adjustment, the code below would round the descender to -3,
> +     * resulting in a font that would be one pixel higher than
> +     * intended. */
> +
> +    CGFloat adjusted_descender = [sfont descender] + 0.0001;
> +
>   #ifdef NS_IMPL_GNUSTEP
>       font_info->nsfont = sfont;
>   #else
> @@ -830,7 +839,7 @@
>
>       brect =  [sfont boundingRectForFont];
>       full_height = brect.size.height;
> -    min_height = [sfont ascender] - [sfont descender];
> +    min_height = [sfont ascender] - adjusted_descender;
>       hd = full_height - min_height;
>
>       /* standard height, similar to Carbon. Emacs.app: was 0.5 by default. */
> @@ -845,10 +854,10 @@
>       /* max bounds */
>       font_info->max_bounds.ascent =
>         lrint (hshrink * [sfont ascender] + expand * hd/2);
> -    /* [sfont descender] is usually negative.  Use floor to avoid
> -       clipping descenders. */
> +    /* Descender is usually negative.  Use floor to avoid clipping
> +       descenders. */
>       font_info->max_bounds.descent =
> -      -lrint (floor(hshrink* [sfont descender] - expand*hd/2));
> +      -lrint (floor(hshrink * adjusted_descender - expand * hd/2));
>       font_info->height =
>         font_info->max_bounds.ascent + font_info->max_bounds.descent;
>       font_info->max_bounds.width = lrint (font_info->width);
> @@ -884,7 +893,7 @@
>
>       /* set up metrics portion of font struct */
>       font->ascent = lrint([sfont ascender]);
> -    font->descent = -lrint(floor([sfont descender]));
> +    font->descent = -lrint(floor(adjusted_descender));
>       font->min_width = ns_char_width(sfont, '|');
>       font->space_width = lrint (ns_char_width (sfont, ' '));
>       font->average_width = lrint (font_info->width);
>
>
>
>
> In GNU Emacs 24.0.50.1 (x86_64-apple-darwin10.5.0, NS apple-appkit-1038.35)
>   of 2011-01-14 on macpro.local
> Windowing system distributor `Apple', version 10.3.1038
> configured using `configure  '--with-ns''
>
> Important settings:
>    value of $LC_ALL: nil
>    value of $LC_COLLATE: nil
>    value of $LC_CTYPE: nil
>    value of $LC_MESSAGES: nil
>    value of $LC_MONETARY: nil
>    value of $LC_NUMERIC: nil
>    value of $LC_TIME: nil
>    value of $LANG: nil
>    value of $XMODIFIERS: nil
>    locale-coding-system: nil
>    default enable-multibyte-characters: t
>
> Major mode: ObjC/lw
>
> Minor modes in effect:
>    diff-auto-refine-mode: t
>    subword-mode: t
>    global-auto-revert-mode: t
>    global-cwarn-mode: t
>    minibuffer-electric-file-mode: t
>    recentf-mode: t
>    msb-mode: t
>    display-time-mode: t
>    tooltip-mode: t
>    mouse-wheel-mode: t
>    menu-bar-mode: t
>    file-name-shadow-mode: t
>    global-font-lock-mode: t
>    font-lock-mode: t
>    auto-composition-mode: t
>    auto-encryption-mode: t
>    auto-compression-mode: t
>    column-number-mode: t
>    line-number-mode: t
>    transient-mark-mode: t
>    abbrev-mode: t
>
> Recent input:
> <down>  <down>  <down>  <down>  <down>  <down>  <down>  <down>
> <down>  <down>  <down>  <down>  <down>  <down>  <down>  <down>
> <down>  <down>  <down>  <down>  <down>  <down>  <down>  <down>
> <down>  <down>  <down>  C-SPC<down>  C-w<down>  C-SPC
> <down>  <down>  <down>  C-w<up>  C-e<left>  <left>  <left>
> <M-backspace>  <backspace>  <backspace>  <backspace>  C-a
> C-x C-s C-M-a C-s e p s C-a C-x C-f s a<backspace>
> l a s j .<backspace>  <backspace>  k . c<return>  <C-tab>
> C-x o<C-S-tab>  C-x p C-M-a<up>  <up>  <up>  <up>  <up>
> <up>  <up>  <up>  <up>  C-SPC<down>  <down>  <down>  <down>
> <down>  <down>  <down>  C-w C-x C-s C-x o C-y C-x p<down>
> C-v C-l C-v<down>  <down-mouse-1>  <mouse-1>  C-a C-SPC
> <down>  <down>  <down>  <down>  <down>  <down>  <down>  C-w
> C-x C-s C-x o C-y C-x C-s C-x p<down-mouse-1>  <mouse-1>
> M-d M-d M-d c o u l y<backspace>  d SPC<backspace>
> M-f<backspace>  <backspace>  <backspace>  y<escape>
> q<M-left>  <M-left>  <M-backspace>  <escape>  q<down>
> <down>  M-f M-f M-f<M-backspace>  t h e SPC d e s c
> M--<escape>  q C-x C-s<down-mouse-1>  <mouse-1>  <down-mouse-1>
> <mouse-1>  <backspace>  C-a C-x C-s<down-mouse-1>  <mouse-1>
> SPC<down-mouse-1>  <mouse-1>  SPC C-a C-x C-s<down-mouse-1>
> <mouse-1>  SPC<down-mouse-1>  <mouse-1>  SPC C-a C-x
> C-s<down-mouse-1>  <mouse-1>  C-a<down>  SPC<backspace>
> <down>  <down>  <down>  <down>  <down>  <up>  SPC<backspace>
> C-a C-x C-s<up>  <up>  <up>  <up>  M-f<right>  <right>
> C-s C-w C-s C-a<down-mouse-1>  <mouse-1>  a<backspace>
> a d j u s t m e n t<escape>  d<escape>  q<up>  <up>
> <up>  C-a C-SPC<down>  <down>  <down>  <down>  <down>  <down>
> <escape>  x i s p l l<backspace>  <backspace>  e l l
> - r e g<tab>  '<backspace>  <return>  q<up>  C-g<up>
> <down-mouse-1>  <mouse-1>  c<escape>  q<down-mouse-1>
> <mouse-1>  C-d<backspace>  <backspace>  <backspace>  i
> f y C-a C-x C-s<menu-bar>  <help-menu>  <send-emacs
> -bug-report>
>
> Recent messages:
> Wrote /Users/anders/build/emacs/trunk/src/nsfont.m
> Mark saved where search started
> Mark set
> Starting new Ispell process [default] ...
> Entering debugger...
> Back to top level.
> Quit
> Auto-saving...done
> Saving file /Users/anders/build/emacs/trunk/src/nsfont.m...
> Wrote /Users/anders/build/emacs/trunk/src/nsfont.m
>
> Load-path shadows:
> ~/emacs/lisp/table hides
> /Applications/Emacs24.app/Contents/Resources/lisp/textmodes/table
> ~/emacs/lisp/ruby-mode hides
> /Applications/Emacs24.app/Contents/Resources/lisp/progmodes/ruby-mode
> ~/emacs/src/asm-mode-new/src/asm-mode hides
> /Applications/Emacs24.app/Contents/Resources/lisp/progmodes/asm-mode
>
> Features:
> (ispell smerge-mode diff-mode texinfo autoconf autoconf-mode conf-mode
> shadow sort gnus-util mail-extr message rfc822 mml mml-sec mm-decode
> mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045 ietf-drums
> mm-util mail-prsvr mailabbrev mail-utils gmm-utils mailheader emacsbug
> subword newcomment ctypes grep compile etags jka-compr find-func follow
> my-end-of-buffer-log c-electric-operator c-indent-operator dired-aux
> dired vc-bzr sha1 hex-util add-log vc-dispatcher vc-svn pp apropos
> multi-isearch debug dabbrev help-mode eldoc ps-print ps-def lpr
> autorevert folding-isearch folding view rdebug cwarn prepaint cc-mode
> cc-fonts cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
> tempo edg-mode split-nways toggle-file-read-only lockdir uniquify
> ange-ftp comint regexp-opt ring paren mic-paren iso-insert
> minibuf-elfile easy-mmode recentf tree-widget wid-edit easymenu msb
> edmacro kmacro warnings disp-table time advice help-fns advice-preload
> cl tooltip ediff-hook vc-hooks lisp-float-type mwheel ns-win tool-bar
> dnd fontset image fringe lisp-mode register page menu-bar rfn-eshadow
> timer select scroll-bar mouse jit-lock font-lock syntax facemenu
> font-core frame cham georgian utf-8-lang misc-lang vietnamese tibetan
> thai tai-viet lao korean japanese hebrew greek romanian slovak czech
> european ethiopic indian cyrillic chinese case-table epa-hook
> jka-cmpr-hook help simple abbrev loaddefs button minibuffer faces
> cus-face files text-properties overlay md5 base64 format env code-pages
> mule custom widget hashtable-print-readable backquote
> make-network-process ns multi-tty emacs)
>
>

Message #13 received at 7887-done <at> debbugs.gnu.org (full text, mbox):

From: Jan Djärv <jan.h.d <at> swipnet.se>
To: Anders Lindgren <andlind <at> gmail.com>, 7887-done <at> debbugs.gnu.org
Subject: Re: bug#7887: Emacs will render some fonts under Mac OS X one pixel
	too tall (patch supplied)
Date: Sat, 29 Jan 2011 11:39:09 +0100

Anders Lindgren skrev 2011-01-25 18.18:

>
> My original suggesten simply said that anything in the range -2.0 -
> -2.0001 should be treated as -2. The motivation behind this is that
> often a floating-point error is only in the lowest bit or bits. (In
> the case I found, the bits that were set corresponds to the least
> significant mantissa bits of a 32 bit floating-point number, even
> though the number had been converted to 64 bit number along the way.)
>

If it only to handle fp errors, then I guess 0.0001 is OK.  Patch checked in.
I don't have any fonts to test with, so if you can confirm that it is fixed, 
that would be great.

Thanks,

	Jan D.

> On Tue, Jan 25, 2011 at 5:12 PM, Jan Djärv <jan.h.d <at> swipnet.se> wrote:
>> > Sounds like a job for round then.
>> >
>> >        Jan D.
>> >
>> >
>> > Anders Lindgren skrev 2011-01-25 15.45:
>>> >>
>>> >> No, that won't work. Descents are always negative, "floor" is used to
>>> >> treat, for example, -2.5 as -3.0, to avoid clipping. The problem is
>>> >> that is also converts -2.000001 to -3.
>>> >>
>>> >> What I suggested was that we continue to round -2.5 down to -3, but
>>> >> round values very close to -2.0 up to -2.
>>> >>
>>> >> I don't know if this is a general problem, only related to FontForge
>>> >> (an open-source font editor). If it's only related to FontForge, then
>>> >> another solution would be to fix it instead of Emacs.
>>> >>
>>> >>     -- Anders
>>> >>
>>> >>

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.