Re: What happened to the fonts?

On Tue, 1 Feb 2005, Ivan Pascal wrote:

> Marc Aurele La France wrote:
>> I don't know enough about this stuff to answer.  Perhaps someone else will,
>> and deal with http://www.mail-archive.com/devel%40xfree86.org/msg06114.html.

>> In the meantime I've backed out the change that's causing this.

> I investigated this issue.
> In one of next messages Barry Scott mentioned
> " I recall I was seeing code behind XutfTextExtents fail to
>  return any info without the patch - I think it was Xutf8TextExtents."
> Therefore I guess he has problem with Xutf8* ouput functions in non-UTF8
> locale.  And it is a real issue.  These functions don't work without changes
> he proposed.  But after such changes Xmb* output functions don't work.

> Obviously, there is some difference in the interpretation of XLC_LOCALE data
> between these two families (Xutf8* and Xmb*).

> The traditional iso2022 based font system requires that any input string
> be separated into portions where all chars belong to one charset.
> Corresponded converters cut out such portions from a text, label them with
> charset name and pass to the next procedure that finds an appropriate font
> for this portion drawing.

> XLC_LOCALE file contains 'codeset' and 'fontset' records. The 'codeset' records
> describe rules for distinguishing chars of different charsets and chaset names
> suitable for each type of chars.  The 'fontset' records just defines pairs
> 'charset name' <-> 'font encoding name' that tell what font should be used
> for each charset (the string labeled with this chaset name).

> What we see in iso8859-15 locale file (and in many other one-byte encoding
> locales)?
> There are two codeset records

> cs0     { side            GL:Default
> ......
>          ct_encoding     ISO8859-15:GL; ISO8859-1:GL }
> cs1     { side            GR:Default
> ......
>          ct_encoding     ISO8859-15:GR }

> and two fontset records

> fs0     { charset { name            ISO8859-1:GL }
>          font    { primary         ISO8859-15:GL
>                                             .... } }
> fs1     { charset { name            ISO8859-15:GR }
>          font    { primary         ISO8859-15:GR } }

> The second records in both pairs is the simplest case. The codeset record says
> that all 'right side' chars (codes > 127) belongs to the right side of
> ISO8859-15 charset and the fontset record says that the text portion labeled
> with 'right side of ISO8859-15 charset' can be drawn with some ISO8859-15
> encoded font.

> The first fontset record is simple too.  It says that 'ISO8859-1 left side'
> labeled string can be writen with ISO8859-15 encoded font.

> But the first codeset record is more complex.  It contains two charset names
> for the same kind of chars ('left side', i.e. codes < 128).  And Xutf8* and
> Xmb* functions use different names from this pair.  (I know why, and can
> explain.  But here I omit those details.)

> Thus if one wants to output simple ASCII string like 'abcd', the 'mb' converter
> labels it as 'ISO8859-1: GL' whereas the 'utf8' converter labels it as
> 'ISO8859-15:GL'.
> And if the fontset record looks like 'charset: ISO8859-1 -> font: ISO8859-15'
> the second step procedure successfuly finds appropriate font for 'mb' converter
> output string but can do nothing for 'utf8' converter output.  And after Barry's
> changes we got a reverse situation: the first fontset record became
> 'charset: ISO8859-15 -> font: ISO8859-15' that means that 'utf8' converter
> output has appropriate font but there is nothing useful for the 'mb' converter
> results.

> The worst thing is that there is significant difference in these converters
> internals and if even we force the 'utf8' converter to choose ISO8859-1
> charset we will not get the the behavior similar to 'mb' converters one.
> In this case the 'utf8' converter makes the 'right side' chars labeled with
> ISO8859-1:GR (execept the Euro sign).  But such name also has not appropriate
> chaset->font pair among fontset records.

> I would suggest a simple workaround: instead of changing the first fontset
> record add a similar one but with another charset name.  I.e. the fontset
> section of XLC_LOCALE will look like:

> fs0     { charset {  name            ISO8859-1:GL  }
>          font    {  primary         ISO8859-15:GL   }}
> fs1     { charset {  name            ISO8859-15:GR  }
>          font    {  primary         ISO8859-15:GR   }}
> fs2     { charset {  name            ISO8859-15:GL  }
>          font    {  primary         ISO8859-15:GL   }}
> In such case the first record would satisfy Xmb* functions and the third record
> would make Xutf8* functions happy.
> (Of course, I tested this solution.  It works.)

OK.  This makes some sense to me.  But should something like this be done to 
all affected locates?

Marc.

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