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On Tue, Jan 18, 2005 at 10:57:10PM +0100, Hartmut Henkel wrote:
On Mon, 15 Nov 2004, Hans Hagen wrote:
The Thanh Han wrote:
I have been thinking of the question how to make char protrusion work with the first char of a paragraph. The simplest (and quite robust) solution can be as follows: when considering whether a marginal kern should be inserted, we skip certain kinds of `invisible' node (like adjust node, penalty node and the like). Now to make it work with the first char of a par, we also skip null boxes (box with zero dimen and empty contents) at the left margin. The question is whether such behaviour is ``correct'', and what surprises it can bring in certain situations.
there are several solutions possible:
<nothing><null box>text text text text
here it looks safe to me to do as you suggest, it can of course be made into an option, say \pdfprotrudeparstart=1 or so
<something><null box>text text text text
these two cases i tried to handle in the experimental patch 257. At paragraph start the empty \hbox{} inserted by TeX is skipped, if \parindent=0pt. Else, inside the paragraph the discardable items at line start are skipped. Then the cp_skipable things are skipped, while diving in and out \hboxes, if any.
is more tricky since one may use the box in order to prevent protruding; on the other hand, if you ignore all null boxes, then it maybe nice to have something
\noprotrusion, which introduces a special node, which in itself may be tricky, although pdftex introduces new nodes anyway
Also any empty or non-empty box with some height or depth does this, e. g. "\vphantom." Maybe that's enough?
definitively. How to *block* protrusion is trivial. How to make it work is more tricky :)
I can also imagine something \pdfprotrudeleft (and right) that can be inserted manually (or everypar'd; in that case it would be handy to finally have \everyendpar available as well); imagine:
\pdfprotrudeleft \hbox {somechar} some text
\pdfprotrudeleft \hbox {\hbox {somechar}} some text
at least now it would find "somechar" inside the box if this is protrudable.
making char protrusion work with metarial inside boxes is already a bug step and would solve a lot of problems.
how difficult is it to let pdftex in that case follow the list until it finds a char (here 's'); this woudl permit things like
\pdfprotrudeleft \hbox {x\hskip-2pt x} some text
To _hide_ the whole \hbox until "s" is found and active at the margin?
Or should one allow protrusion of "s" in things like \llap{foo}s?
I don't know what it can be good for. If there is a need to protrude something that is not a character, using some virtual character may solve the problem faster. Thanh