[devel] XLFD font naming convention

[Lucien Gentis]

Le 04/03/2019 à 19:09, Ilya Anfimov a écrit :
> On Mon, Mar 04, 2019 at 07:03:00PM +0100, Lucien Gentis wrote:
>>     Le 04/03/2019 `a 18:18, Ilya Anfimov a ecrit :
>>
> [skipped]
>
>>      "For a scalable font source, a scalable font name for each
>>      character set is included in the list.  In addition to
>>      the scalable font name, specific derived instance names
>>      may also be included in the list."
>>      ...
>>      "Because some existing applications rely on seeing a collection
>>      of point and pixel sizes, server vendors are strongly
>>      encouraged in the near term to provide a mechanism for
>>      including, for each scalable font name, a set of specific
>>      derived instance names. For font sources that contain a set of
>>      specific derived instance names."
>>
>>     So  it  is OK to have that in font list. It must be --0-0-  base
>>   name for every such font, and if it is not -- there is  an  error
>>   somewhere in your X server or font server, and probably should be
>>   fixed. If there are base entries -- then you  don't need them.
>>
> [skipped]
>
>>     I don't really need it, existing choice is big enough !
>>
>   Probably you somewhat misread my description.
>   It  should  be  not big enough, it should contain all that fonts
> with proper fields zeroed.
>   If it does not -- it is some error in server.
>
>
>
>>     But I only wanted to know the signification of "0" field in -adobe-new
>>     century schoolbook-bold-r-normal--0-120-100-100-p-0-iso10646-1
>>
>>     I did these (easy to reproduce) tests with xfontsel and xlsfonts commands
>>     :
>>
>>     xfontsel :
>>
>>     - if we select a point size of 120, it's impossible to select a pixel size
>>     of 0
>>
>>     - if we select a pixel size of 0, we only have the choice between * or 0
>>     for point size
>>
>>     xlsfonts :
>>
>>     - xlsfonts -fn "-*-*-*-*-*-*-0-*-*-*-*-*-*-*" (pixel size of 0) : we can
>>     see scalable fonts and fonts like -adobe-new century
>>     schoolbook-bold-r-normal--0-120-100-100-p-0-iso10646-1
>>
>>     - xlsfonts -fn "-*-*-*-*-*-*-0-120-*-*-*-*-*-*" (pixel size of 0, point
>>     size of 120) : we can see fonts like -adobe-new century
>>     schoolbook-bold-r-normal--0-120-100-100-p-0-iso10646-1
>>
>>     - xlsfonts -fn "-*-*-*-*-*-*-*-120-*-*-*-*-*-*" (point size of 120) :we
>>     don't see anymore fonts like -adobe-new century
>>     schoolbook-bold-r-normal--0-120-100-100-p-0-iso10646-1, which is confusing
>>     because "-*-120-" also matches "-0-120-"
>>
>>
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>
There is no server error.

The answer is at the end of chapter 5 of 
https://www.x.org/releases/X11R7.7/doc/xorg-docs/xlfd/xlfd.html#Scalable_Fonts 
where it is said:

"if the actual pattern argument (of ListFonts X query) has values 
containing no wildcards in scalable fields, then substitute each such 
field into the corresponding field in each scalable font name in the list."

So as I understand, if we call xlsfonts -fn 
"-*-*-*-*-*-*-0-0-*-*-*-0-*-*" (Pixel size, point size and average width 
at 0), we get all scalable fonts, and if we call xlsfonts -fn 
"-*-*-*-*-*-*-0-138-*-*-*-*-*-*" (Pixel size at 0 and point size of 138) 
or xlsfonts -fn "-*-*-*-*-*-*-*-138-*-*-*-0-*-*" (Point size of 138 and 
average size at 0), we get all scalable font *instances* with a point 
size of 138 and some default resolutions.

120 seems to be something like a default point size value and 17 a 
default pixel size when these values are not specified. try to call 
xlsfonts -fn "-*-*-*-*-*-*-0-*-*-*-*-*-*-*" or xlsfonts -fn 
"-*-*-*-*-*-*-*-0-*-*-*-*-*-*"

I already thank you Ilya for your help and spoting to the XLFD doc that 
is not easy to find

Lucien

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