Tidy and HTML tab spacing

[Warren Block]

On Thu, 19 Jan 2012, Hiroki Sato wrote:

> It is difficult to solve this issue completely because the result
> text can be obtained only by a complete HTML processor such as www
> browsers.  I don't have a good idea, but I think it is not a bad idea
> to use a tab character (or replacing it to 	) in the result text
> by modifying Tidy and leave the processing to www browsers.

The suggestion of 	 is interesting.  The problem is that tidy is 
changing tabs to spaces while still reading the file, when it really 
should be treating the tab as a special entity while processings tags.

So preprocessing still might be a way to preserve tabs.  Just convert 
them all to 	 before tidy has a chance to change them.

   perl -i -pe 's/\t/	/g' book.html

sed works also, but beware of the binary tab necessary for sed's 
paleolithic regexes:

   sed -i -e 's/	/\	/g' book.html

Initial testing shows this does seem to work.  The output has genuine
tabs which display fine in Firefox but ought to be tested in other 
browsers.  Note that there are some invisible tabs in the HTML output 
that come from the SGML source.  For example, the copyright notice in 
the Porter's Handbook:

       <holder role="mailto:doc at FreeBSD.org">The FreeBSD Documentation
 	Project</holder>

That leading tab on the second line is in the HTML file.  Still, 
replacing those invisible tabs with 	 instead of spaces should 
render the same.


Finally, before picking up on the idea of tab-as-an-entity, I worked up 
a patch to www/tidy-devel which uses the magic value of --tab-size 255 
to mean "don't replace tabs".  Attached, but I think the 	 is 
better.
-------------- next part --------------
--- src/streamio.c.orig	2008-03-22 15:00:18.000000000 -0600
+++ src/streamio.c	2012-01-20 12:25:58.000000000 -0700
@@ -351,11 +351,18 @@
             added = yes;
             TY_(AddCharToOriginalText)(in, (tchar)c);
 #endif
-            in->tabs = tabsize > 0 ?
-                tabsize - ((in->curcol - 1) % tabsize) - 1
-                : 0;
-            in->curcol++;
-            c = ' ';
+            if (tabsize == 255) {
+                in->curcol++;
+                c = '\t';
+            }
+            else
+            {
+                in->tabs = tabsize > 0 ?
+                    tabsize - ((in->curcol - 1) % tabsize) - 1
+                    : 0;
+                in->curcol++;
+                c = ' ';
+            }
             break;
         }