Inaccuracy in NEWS.28

Inaccuracy in NEWS.28

[Po Lu]

NEWS.28 says:

  Note that building with Cairo means using Pango instead of libXFT for
  font support.  Since Pango 1.44 has removed support for bitmapped
  fonts, this may require you to adjust your font settings.

But we don't use Pango anywhere except to parse GTK input method
information and the output of the GTK font dialog.

Cairo text display is unrelated to Pango, and bitmapped fonts will work
there as long as they are supported by FreeType.  Bitmapped fonts will
also continue to work with the X server-side font driver, which is
available in Cairo builds.

So would anyone mind me simply deleting that part of NEWS.28, since it
is plain out wrong?

Re: Inaccuracy in NEWS.28

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Date: Tue, 01 Mar 2022 12:54:01 +0800
> 
> NEWS.28 says:
> 
>   Note that building with Cairo means using Pango instead of libXFT for
>   font support.  Since Pango 1.44 has removed support for bitmapped
>   fonts, this may require you to adjust your font settings.
> 
> But we don't use Pango anywhere except to parse GTK input method
> information and the output of the GTK font dialog.
> 
> Cairo text display is unrelated to Pango, and bitmapped fonts will work
> there as long as they are supported by FreeType.  Bitmapped fonts will
> also continue to work with the X server-side font driver, which is
> available in Cairo builds.
> 
> So would anyone mind me simply deleting that part of NEWS.28, since it
> is plain out wrong?

I'm not sure it's so plain wrong.  This text came out of prolonged
discussions we had back in January 2020 on emacs-devel, and it started
with this report:

  https://lists.gnu.org/archive/html/emacs-devel/2020-01/msg00583.html

Please read that discussion, and also the followups:

  https://lists.gnu.org/archive/html/emacs-devel/2020-01/msg00620.html
  https://lists.gnu.org/archive/html/emacs-devel/2020-01/msg00739.html
  https://lists.gnu.org/archive/html/emacs-devel/2020-01/msg00870.html

Maybe the description we now have in NEWS.28 is inaccurate, but the
problems were real.  So if you think mentioning Pango there is
incorrect (but please explain why, as I don't think I agree with your
reasoning: AFAIK Pango is the text layout engine used by Cairo), then
perhaps we should say something different there to convey the same
message.  And the message is still valid, AFAIK.

Re: Inaccuracy in NEWS.28

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

> So if you think mentioning Pango there is incorrect (but please
> explain why, as I don't think I agree with your reasoning: AFAIK Pango
> is the text layout engine used by Cairo)

Pango is a text layout and font management library which operates on a
much higher level than cairo.  It performs bidirectional reordering, and
delegates to HarfBuzz for text shaping, along with using FreeType for
calculating glyph metrics and for opening fonts, and fontconfig to
enumerate fonts.

Cairo is one of the many libraries that Pango can use to display glyphs
onto the glass, but is otherwise unrelated to Pango.

However, judging by those discussions, there does seem to be some
problems with cairo and bitmap fonts.  So how about saying this instead:

  Building with Cairo is known to cause some problems with bitmap fonts.
  This may require you to adjust your font settings, or to build with
  Xft support instead.

Thanks.

Re: Inaccuracy in NEWS.28

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Tue, 01 Mar 2022 20:46:59 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > So if you think mentioning Pango there is incorrect (but please
> > explain why, as I don't think I agree with your reasoning: AFAIK Pango
> > is the text layout engine used by Cairo)
> 
> Pango is a text layout and font management library which operates on a
> much higher level than cairo.  It performs bidirectional reordering, and
> delegates to HarfBuzz for text shaping, along with using FreeType for
> calculating glyph metrics and for opening fonts, and fontconfig to
> enumerate fonts.
> 
> Cairo is one of the many libraries that Pango can use to display glyphs
> onto the glass, but is otherwise unrelated to Pango.

Robert, do you agree?

> However, judging by those discussions, there does seem to be some
> problems with cairo and bitmap fonts.  So how about saying this instead:
> 
>   Building with Cairo is known to cause some problems with bitmap fonts.
>   This may require you to adjust your font settings, or to build with
>   Xft support instead.

Please show a complete patch, it's hard to guess which text you'd like
to replace with this.

Thanks.

Re: Inaccuracy in NEWS.28

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

> Please show a complete patch, it's hard to guess which text you'd like
> to replace with this.

Sure, thanks:

diff --git a/etc/NEWS.28 b/etc/NEWS.28
index 58c7c44a2b..84041d79c2 100644
--- a/etc/NEWS.28
+++ b/etc/NEWS.28
@@ -43,11 +43,10 @@ recommend examining any such warnings before you decide they are
 false.
 
 ** The Cairo graphics library is now used by default if present.
-'--with-cairo' is now the default, if the appropriate development files
-are found by 'configure'.  Note that building with Cairo means using
-Pango instead of libXFT for font support.  Since Pango 1.44 has
-removed support for bitmapped fonts, this may require you to adjust
-your font settings.
+'--with-cairo' is now the default, if the appropriate development
+files are found by 'configure'.  Building with Cairo is known to cause
+some problems with bitmap fonts.  This may require you to adjust your
+font settings, or to build with Xft support instead.
 
 Note also that 'FontBackend' settings in ".Xdefaults" or
 ".Xresources", or 'font-backend' frame parameter settings in your init

Re: Inaccuracy in NEWS.28

[Robert Pluim]

>>>>> On Tue, 01 Mar 2022 21:22:12 +0800, Po Lu <luangruo@yahoo.com> said:

    Po> Eli Zaretskii <eliz@gnu.org> writes:
    >> Please show a complete patch, it's hard to guess which text you'd like
    >> to replace with this.

    Po> Sure, thanks:

    Po> diff --git a/etc/NEWS.28 b/etc/NEWS.28
    Po> index 58c7c44a2b..84041d79c2 100644
    Po> --- a/etc/NEWS.28
    Po> +++ b/etc/NEWS.28
    Po> @@ -43,11 +43,10 @@ recommend examining any such warnings before you decide they are
    Po>  false.
 
    Po>  ** The Cairo graphics library is now used by default if present.
    Po> -'--with-cairo' is now the default, if the appropriate development files
    Po> -are found by 'configure'.  Note that building with Cairo means using
    Po> -Pango instead of libXFT for font support.  Since Pango 1.44 has
    Po> -removed support for bitmapped fonts, this may require you to adjust
    Po> -your font settings.
    Po> +'--with-cairo' is now the default, if the appropriate development
    Po> +files are found by 'configure'.  Building with Cairo is known to cause
    Po> +some problems with bitmap fonts.  This may require you to adjust your
    Po> +font settings, or to build with Xft support instead.
 
    Po>  Note also that 'FontBackend' settings in ".Xdefaults" or
    Po>  ".Xresources", or 'font-backend' frame parameter settings in your init

I think this is fine. Note we do call some Pango api's when using the
GTK font chooser, but I suspect you could never choose a bitmapped
font that way anyway.

Robert
-- 

Re: Inaccuracy in NEWS.28

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org
> Date: Tue, 01 Mar 2022 14:47:31 +0100
> 
>     Po>  ** The Cairo graphics library is now used by default if present.
>     Po> -'--with-cairo' is now the default, if the appropriate development files
>     Po> -are found by 'configure'.  Note that building with Cairo means using
>     Po> -Pango instead of libXFT for font support.  Since Pango 1.44 has
>     Po> -removed support for bitmapped fonts, this may require you to adjust
>     Po> -your font settings.
>     Po> +'--with-cairo' is now the default, if the appropriate development
>     Po> +files are found by 'configure'.  Building with Cairo is known to cause
>     Po> +some problems with bitmap fonts.  This may require you to adjust your
>     Po> +font settings, or to build with Xft support instead.
>  
>     Po>  Note also that 'FontBackend' settings in ".Xdefaults" or
>     Po>  ".Xresources", or 'font-backend' frame parameter settings in your init
> 
> I think this is fine. Note we do call some Pango api's when using the
> GTK font chooser, but I suspect you could never choose a bitmapped
> font that way anyway.

OK, so let's install this on the emacs-28 branch.

Thanks.

Re: Inaccuracy in NEWS.28

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Robert Pluim <rpluim@gmail.com>
>> Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org
>> Date: Tue, 01 Mar 2022 14:47:31 +0100
>> 
>>     Po>  ** The Cairo graphics library is now used by default if present.
>>     Po> -'--with-cairo' is now the default, if the appropriate development files
>>     Po> -are found by 'configure'.  Note that building with Cairo means using
>>     Po> -Pango instead of libXFT for font support.  Since Pango 1.44 has
>>     Po> -removed support for bitmapped fonts, this may require you to adjust
>>     Po> -your font settings.
>>     Po> +'--with-cairo' is now the default, if the appropriate development
>>     Po> +files are found by 'configure'.  Building with Cairo is known to cause
>>     Po> +some problems with bitmap fonts.  This may require you to adjust your
>>     Po> +font settings, or to build with Xft support instead.
>>  
>>     Po>  Note also that 'FontBackend' settings in ".Xdefaults" or
>>     Po>  ".Xresources", or 'font-backend' frame parameter settings in your init
>> 
>> I think this is fine. Note we do call some Pango api's when using the
>> GTK font chooser, but I suspect you could never choose a bitmapped
>> font that way anyway.
>
> OK, so let's install this on the emacs-28 branch.

Could Robert or you install this instead, because I don't have a
convenient checkout of the emacs-28 branch lying around right now?

Thanks in advance.

Re: Inaccuracy in NEWS.28

[Robert Pluim]

>>>>> On Wed, 02 Mar 2022 08:56:25 +0800, Po Lu <luangruo@yahoo.com> said:

    Po> Could Robert or you install this instead, because I don't have a
    Po> convenient checkout of the emacs-28 branch lying around right now?

Done. I have worktrees lying around going back to emacs-26 since Iʼm
too lazy to remove them :-)

    Po> Thanks in advance.

np

Robert
-- 

Re: Inaccuracy in NEWS.28

[Po Lu]

Robert Pluim <rpluim@gmail.com> writes:

> Done. I have worktrees lying around going back to emacs-26 since Iʼm
> too lazy to remove them :-)

Thanks.