Re: Font selection algorithm / how do fonts work / what do you suggest for mono font?

[Oleksandr Gavenko <gavenkoa@gmail.com>]

On 2016-09-26, Eli Zaretskii wrote:

>> Actually I have a problem, as I wrote ``terminus`` font missed some glyphs and
>> I expect that:
>> 
>>   (set-fontset-font nil nil "-misc-fixed-*-*-*--13-*-*-*-*-*-*-*")
>> 
>> was as fallback. But it has no effect. Fix with range resolve issue:
>> 
>>   ;; MODIFIER LETTER is not present in terminus, this includes ˌːˈ characters.
>>   (set-fontset-font nil '(#x02C0 . #x02FF) "-misc-fixed-*-*-*--13-*-*-*-*-*-*-*")
>> 
>> Do I need file bug or I am wrong with (set-fontset-font nil nil ...)?
>
> On my system these characters display well by default.  If the problem
> is that these characters are displayed, but you don't like the font
> Emacs selects, I think that's something you should customize 9as you
> did), and not a bug you should report.

I was confused with:

  (set-fontset-font NAME TARGET FONT-SPEC &optional FRAME ADD)

  TARGET may be nil.  In that case, use FONT-SPEC for any characters for
  that no FONT-SPEC is specified.

With "emacs -Q" and:

  (set-frame-font "-*-terminus-medium-r-*--14-*-*-*-c-*-*-*")
  (describe-fontset "default-fontset")

for symbol:

  ː
  code point in charset: 0x02D0

I got at least such ranges that contain 0x02D0:

  ¼ .. Ѐ (#xBC .. #x400)
      -*-*-*-*-*-*-*-*-*-*-*-*-microsoft-cp1251
      [-xos4-terminus-medium-r-normal--14-140-72-72-c-80-microsoft-cp1251]

  ː (#x2D0)
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-1
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-2
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-3
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-4
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-9
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-10
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-13
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-14
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-15
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso8859-16
      [-xos4-Terminus-normal-normal-normal-*-14-*-*-*-c-80-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-viscii1.1-1
      [-unknown-Gentium-normal-normal-normal-*-14-*-*-*-*-0-iso10646-1]
      -*-*-*-*-*-*-*-*-*-*-*-*-iso10646-1
      -*-*-*-*-*-*-*-*-*-*-*-*-ksc5601.1987-0

C-u C-x = shown that "Gentium" font is used for displaying character.

Is that mean that for "ː" character font is defined and so

  (set-fontset-font nil **nil** FONT-SPEC &optional FRAME ADD)

isn't taken in account (when TARGET == nil)?

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