[XeTeX] Line-breaking algorithms in XeTeX

[John Was]

Dear Jonathan

Thanks for this.  I am getting exactly what you get from the test (adding 
that the \parindent = 1em), which tells me that there is something else 
going on in my definitions to cause the problems I described, but a search 
up and down the header file that gets read in at the start of the job 
doesn't throw up anything obvious - and I didn't expect it to since I just 
took these over from an old implementation of TeX, where the problem never 
arose).  I'll have to go through line by line, I think, and get back to you 
if I track anything down.

One thing I've learnt from your sample, though, is that (Xe)TeX selects 
different hyphenation and line-breaking points when the \looseness is 
reduced to -1, even though that doesn't in fact produce a smaller number of 
lines.  I had always assumed that if the line-count ends up the same as if 
\loosness were 0, then the \looseness-1 would be ignored without causing any 
effect at all.

Best wishes


John

----- Original Message ----- 
From: "Jonathan Kew" <jfkthame at googlemail.com>
To: "Unicode-based TeX for Mac OS X and other platforms" <xetex at tug.org>
Sent: Tuesday, April 28, 2009 4:01 PM
Subject: Re: [XeTeX] Line-breaking algorithms in XeTeX


On Mon, Apr 27, 2009 at 1:38 PM, John Was <john.was at ntlworld.com> wrote:
>
> Dear Jonathan
>
> In the sample paragraph I sent you I neglected to say that I also use 1.5
> letter-spacing when I use the font. The actual font call is:
>
> \font \umirtenpointtwofive =
> "MinionPro-Regular:+onum:mapping=tex-text:letterspace=1.5" at 10.25pt
>
> Could that be the culprit?

I don't know.... so far, I haven't been able to reproduce this. I
think there's still some detail of the format (paragraph indent?
hyphenation settings? ....?) that I don't have in order to match your
results. Here's the test file so far:

% % % % % % % % % % % % % % % % % %
% !TEX TS-program = xetex

\font \umirtenpointtwofive =
"MinionPro-Regular:+onum:mapping=tex-text:letterspace=1.5" at 10.25pt
\umirtenpointtwofive
\spaceskip=0.25em plus 0.25em minus 0.075em
\hsize=29pc
\def\cq{\leavevmode \kern 1sp \hbox{'}}

One consequence of these particular choices is that the attempt to revalue
the later Swinburne remains rather thinly established: the close attention
scarcely extends beyond the 1870s. But the more interesting issue is the
matter of choice itself. Clearly the sympathetic overviews attempted by
Grierson and Fletcher failed to rescue Swinburne{\cq}s reputation: he
remains a marginal figure, with few enthusiastic readers and a minimal
presence in the academic syllabus. Does a highly selective but more closely
observed account of his work provide a more effective argument for his
value?\looseness=-1

One consequence of these particular choices is that the attempt to revalue
the later Swinburne remains rather thinly established: the close attention
scarcely extends beyond the 1870s. But the more interesting issue is the
matter of choice itself. Clearly the sympathetic overviews attempted by
Grierson and Fletcher failed to rescue Swinburne{\cq}s reputation: he
remains a marginal figure, with few enthusiastic readers and a minimal
presence in the academic syllabus. Does a highly selective but more closely
observed account of his work provide a more effective argument for his
value?

\end
% % % % % % % % % % % % % % % % % %

This seems to work fine for me: both versions of the paragraph are set
as 8 lines, although not identically as the first one gets some
hyphenation; but no overfull boxes. Could you try this, and adjust
whatever is necessary until it actually reproduces the problem you're
seeing? I need an actual runnable example if I'm going to get to the
root of this.

Thanks,

Jonathan
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