[NTG-pdftex] [ pdftex-Feature Requests-743 ] Fake beginning/end of line for protrusion

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Feature Requests item #743, was opened at 2007-03-06 02:20
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Category: HZ
Group: v1.50
Status: Open
Resolution: Accepted
Priority: 5
Submitted By: Robert (schlcht)
Assigned to: The Thanh Han (hanthethanh)
Summary: Fake beginning/end of line for protrusion

Initial Comment:
Although the situation with missing protrusion has
certainly improved, there are still a lot of cases
where characters will not be protruded (e.g. with
indented paragraphs, at the beginning of list items, or
of table cells).
So I think it would be useful to have some commands
that make pdftex believe that it is at the beginning or
end of a line (e.g. \protchar{left,right}). So that you
could for instance say:
 \item\protcharleft ``...
Difficult?


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>Comment By: The Thanh Han (hanthethanh)
Date: 2007-03-07 09:52

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yes inserting a whatsit node that would be changed to a kern
seems the easiest way. I will give a try soon.

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Comment By: Robert (schlcht)
Date: 2007-03-06 17:21

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Maybe new (whatsit) nodes that can be caught in
find_protchar_left/right?

microtype is quite good in translating characters into slots
(\MT at get@slot), but not really good enough to always allow
natural input, e.g., ligatures and things like "` (German
babel) won't be recognised.
So my current workaround is:

\def\protcharleft#1{%
  {\everypar{}%
   \setbox0\vbox{\noindent#1}%
   \vbadness=10000
   \splittopskip=0pt
   \global\setbox0=\vsplit0 to \baselineskip
   \unvbox0 \global\setbox0=\lastbox}%
  \ifhbox0
    \leavevmode
    \kern\leftmarginkern0
  \fi
  #1}

But this doesn't always work, e.g. in tabulars. Ligatures
and other stuff still have to be enclosed in braces.


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Comment By: Taco Hoekwater (taco)
Date: 2007-03-06 08:00

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I will be experimenting with Aleph's \localleftbox somewhere
next month, that may be a starting point. But it is 
unlikely that any command based on that will be able to
influence line breaking.

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Comment By: The Thanh Han (hanthethanh)
Date: 2007-03-06 07:52

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yes it makes sense. I am not sure whether \protcharleft
could be implemented as macro: one can fetch the next char,
get the lpcode and do a corresponding kern. However I don't
know how to convert a character to its charcode to fetch the
relevant lpcode. Another problem is that if the next char is
part of a ligature (as in your example), it doesn't work.
Looks like a primitive is needed. Does anyone have a
suggestion how it could be implemented?


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