Improve CJK support with new values for `.cflags'.

This patch introduces three new values to `.cflags':

  don't break before character: 128
  don't break after character:  256
  allow inter-character break:  512

They are handled differently if compared to other cflags values:

  (1) hcode values are completely ignored
  (2) similar to kern values, and contrary to the other cflags
      values, troff looks at pairs of characters to decide whether a
      break gets inserted

A yet-to-be-written patch should add inter-character spacing if
those flags are active; currently, only zero-width breakpoints are
inserted.

* src/roff/troff/charinfo.h (charinfo): Change type of `flags' to
`int'.  Update callers accordingly.
New enum values `DONT_BREAK_BEFORE', `DONT_BREAK_AFTER', and
`INTER_CHAR_SPACE'.
New member functions `prohibit_break_before',
`prohibit_break_after', and `inter_char_space'.
* src/roff/troff/input.cpp: Updated.

* src/roff/troff/node.cpp (inter_char_space_node): New class similar
to kern_pair_node, collecting charinfo entities with the
abovementioned cflags values.
(break_char_type): Add new enum values.
(glyph_node::merge_glyph_node): Handle abovementioned cflags values
and emit an `inter_char_space_node' if necessary.

* tmac/ja.tmac: Use new cflags values.

* doc/groff.texinfo, NEWS, man/groff_diff.man: Document new values.

1 files changed, 7 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 00a41b47..ce6410cc 100644
--- a/NEWS
+++ b/NEWS
@@ -28,6 +28,13 @@ o The new `class' request assigns a short name to a set of characters
   which can be referred to in the `cflags' request.  This is especially
   useful to control line-breaking and hyphenation rules in CJK languages.
 
+o Three new values for the `cflags' request have been added, which are
+  needed for proper CJK support.
+
+    128  prohibit before but allow break after character
+    256  prohibit after but allow break before character
+    512  allow break before and after character
+
 Tbl
 ---