@x
{margin int_pars go here}
@y
@d default_margin_char_code=81
@z

@x
@d error_context_lines==int_par(error_context_lines_code)
@y
@d error_context_lines==int_par(error_context_lines_code)
@d default_margin_char==int_par(default_margin_char_code)
@z

@x
error_context_lines_code:print_esc("errorcontextlines");
@y
error_context_lines_code:print_esc("errorcontextlines");
default_margin_char_code:print_esc("defaultmarginchar");
@z

@x
primitive("errorcontextlines",assign_int,int_base+error_context_lines_code);@/
@!@:error_context_lines_}{\.{\\errorcontextlines} primitive@>
@y
primitive("errorcontextlines",assign_int,int_base+error_context_lines_code);@/
@!@:error_context_lines_}{\.{\\errorcontextlines} primitive@>
primitive("defaultmarginchar",assign_int,int_base+default_margin_char_code);@/
@!@:default_margin_char_}{\.{\\defaultmarginchar} primitive@>
@z

@x
@!font_false_bchar:array[internal_font_number] of min_quarterword..non_char;
 {|font_bchar| if it doesn't exist in the font, otherwise |non_char|}
@y
@!font_false_bchar:array[internal_font_number] of min_quarterword..non_char;
 {|font_bchar| if it doesn't exist in the font, otherwise |non_char|}
@!margin_char:array[internal_font_number] of integer;
 {current \.{\\marginchar} values}
@z

@x
for k:=0 to 6 do font_info[k].sc:=0;
@y
for k:=0 to 6 do font_info[k].sc:=0;
margin_char[null_font]:=-1;
@z

@x
hyphen_char[f]:=default_hyphen_char; skew_char[f]:=default_skew_char;
@y
hyphen_char[f]:=default_hyphen_char; skew_char[f]:=default_skew_char;
margin_char[f]:=default_margin_char;
@z

@x
@d copy_to_cur_active(#)==cur_active_width[#]:=active_width[#]
@d deactivate=60 {go here when node |r| should be deactivated}

@<Declare subprocedures for |line_break|@>=
@y
The function |kerning| returns the kerning between the characters
|cl| and |cr| in font |f|, or zero if there is none.

@d copy_to_cur_active(#)==cur_active_width[#]:=active_width[#]
@d deactivate=60 {go here when node |r| should be deactivated}

@<Declare subprocedures for |line_break|@>=
function kerning(f,cl,cr:eight_bits):scaled;
label done;
var s:scaled;
i:four_quarters;
a:integer;
begin
 s:=0;
 i:=char_info(f)(cl);
 if char_tag(i)=lig_tag then begin
   a:=lig_kern_start(f)(i);
   i:=font_info[a].qqqq;
   if skip_byte(i)>stop_flag then begin
     a:=lig_kern_restart(f)(i);
     i:=font_info[a].qqqq;
   end;
   loop@+ begin
     if next_char(i)=cr then begin
       if op_byte(i)>=kern_flag then
         if skip_byte(i)<=stop_flag then s:=char_kern(f)(i);
       goto done;
     end;
     if skip_byte(i)>=stop_flag then goto done;
     a:=a+qo(skip_byte(i))+1;
     i:=font_info[a].qqqq;
   end;
 end;
done: kerning:=s;
end;

@ The function |margin_correction| expects an active node |r| and
a |cur_p| pointing directly into the horizontal list with the tentative
line to be broken extending from |r| to |cur_p|.

It returns the sum of the margin corrections for the line between them. It
does so by finding the first node in the line, skipping everything that would
be dropped after a break (including a possible |\parindent| box), and
calculating the kern between the |marginchar| and it. Similarly, the last node
of the line is used to find the kern between it and the |marginchar|. This
routine could be made more efficient by avoiding the list traversal. The main
loop of |try_break| could remember the last node before |cur_p|.

@<Declare subprocedures for |line_break|@>=
function margin_correction(r,cur_p:pointer):scaled;
label done;
var left_kern,right_kern:scaled;
sl,s:pointer;
f,c:eight_bits;
ii:four_quarters;
rc,a:integer;
begin
 left_kern:=0;
 right_kern:=0;
 if break_node(r)=null then begin
   sl:=temp_head;
   if (type(link(sl))=hlist_node)and
          (list_ptr(link(sl))=null) then begin
     sl:=link(sl); { skip |\parindent| box }
   end;
 end else sl:=cur_break(break_node(r));
 s:=sl;
 if type(s)=disc_node then begin
   if post_break(s)<>null then s:=post_break(s)
   else begin
     rc:=replace_count(s);
     s:=link(s);
     while rc>0 do begin
       if link(s)<>null then s:=link(s);
       decr(rc);
     end;
   end;
 end;
 f:=null_font; c:=qi(0);
 while s<>null do begin
   if is_char_node(s) then begin
     f:=font(s); c:=character(s);
     s:=null;
   end else case type(s) of
     glue_node: s:=link(s);
     penalty_node: s:=link(s);
     ligature_node: begin
       f:=font(lig_char(s));
       c:=character(lig_char(s));
       s:=null;
     end;
     math_node: s:=link(s);
     kern_node: if subtype(s)<>explicit then s:=null else s:=link(s);
     othercases s:=null;
   endcases;@/
 end;
 { if we reach this point, |(f,c)| is the font-char pair starting the line }
 if (0<=margin_char[f])and(margin_char[f]<=255) then begin
   left_kern:=kerning(f,qi(margin_char[f]),c);
 end;

 s:=null;
 if cur_p then
   if type(cur_p)=disc_node then begin
     if pre_break(cur_p)<>null then begin
       s:=pre_break(cur_p);
       while link(s)<>null do s:=link(s); { unnecessary list traversal! }
       goto done;
     end;
   end;
 s:=sl;
 while link(s)<>cur_p do begin
   s:=link(s);
   if s=null then goto done;
 end;
done:
 f:=null_font; c:=qi(0);
 if s<>null then if is_char_node(s) then begin
   f:=font(s); c:=character(s);
 end else if type(s)=ligature_node then begin
   f:=font(lig_char(s));
   c:=character(lig_char(s));
 end;
 { if we reach this point, |(f,c)| is the font-char pair ending the line }
 if (0<=margin_char[f])and(margin_char[f]<=255) then begin
   right_kern:=kerning(f,c,qi(margin_char[f]));
 end;
margin_correction:=left_kern+right_kern;
end;
@z

@x
@!line_width:scaled; {the current line will be justified to this width}
@y
@!line_width:scaled; {the current line will be justified to this width}
@!local_line_width:scaled; {|line_width| including |marginchar| kerning}
@z

@x
if hz_en then begin
 if cur_active_width[1]+cur_active_width[7]<line_width then
   shortfall:=line_width-(cur_active_width[1]+cur_active_width[7])
 else if cur_active_width[1]-cur_active_width[8]>line_width then
   shortfall:=line_width-(cur_active_width[1]-cur_active_width[8])
 else shortfall:=0;
end else shortfall:=line_width-cur_active_width[1]; {we're this much too short}
@y
local_line_width:=line_width-margin_correction(r,cur_p);
if hz_en then begin
 if cur_active_width[1]+cur_active_width[7]<local_line_width then
   shortfall:=line_width-(cur_active_width[1]+cur_active_width[7])
 else if cur_active_width[1]-cur_active_width[8]>local_line_width then
   shortfall:=line_width-(cur_active_width[1]-cur_active_width[8])
 else shortfall:=0;
end else shortfall:=local_line_width-cur_active_width[1]; {we're this much too short}
@z

@x
procedure post_line_break(@!final_widow_penalty:integer);
label done,done1;
var q,@!r,@!s:pointer; {temporary registers for list manipulation}
@y
procedure post_line_break(@!final_widow_penalty:integer);
label done,done1,done2,done3;
var q,@!r,@!s:pointer; {temporary registers for list manipulation}
f,c:eight_bits;
ss:scaled;
@z

@x
@<Modify the end of the line to reflect the nature of the break and to include
 \.{\\rightskip}; also set the proper value of |disc_break|@>;
@<Put the \(l)\.{\\leftskip} glue at the left and detach this line@>;
@y
@<Modify the end of the line to reflect the nature of the break and to include
 \.{\\rightskip}; also set the proper value of |disc_break|@>;
@<Put the \(l)\.{\\leftskip} glue at the left and detach this line@>;
@<Deal with the \.{\\marginchar} kerning@>;
@z

@x
@<Put the \(l)\.{\\leftskip} glue at the left...@>=
r:=link(q); link(q):=null; q:=link(temp_head); link(temp_head):=r;
if left_skip<>zero_glue then
 begin r:=new_param_glue(left_skip_code);
 link(r):=q; q:=r;
 end
@y
We change this code to always insert the \.{\\leftskip}.

@<Put the \(l)\.{\\leftskip} glue at the left...@>=
r:=link(q); link(q):=null; q:=link(temp_head); link(temp_head):=r;
r:=new_param_glue(left_skip_code);
link(r):=q; q:=r

@ When we reach this code, |q| points to the line in question. The line starts
with \.{\\leftskip} glue and ends with \.{\\rightskip} glue. If the first node
after the |leftskip| is a character~|c| whose font has a |marginchar|~|m|, we
insert the kerning |m|--|c| between the |leftskip| node and charnode~|c|.

If the last node before the |rightskip is a character~|c'| whose font has a
|marginchar|~|m'|, we insert the kerning |c'|--|m'| between charnode~|c'|
and the |rightskip| node.

@<Deal with the \.{\\marginchar} kerning@>=
s:=q; r:=link(s);
if cur_line=prev_graf+1 then begin {treat the first line specially}
 if (type(r)=hlist_node)and(list_ptr(r)=null) then begin {skip |parindent| box}
   s:=r; r:=link(s);
 end;
end;
ss:=0;
if is_char_node(r) then begin
 f:=font(r); c:=character(r);
end else if type(r)=ligature_node then begin
 f:=font(lig_char(r)); c:=character(lig_char(r));
end else goto done2;
if (0<=margin_char[f])and(margin_char[f]<=255) then begin
 ss:=kerning(f,qi(margin_char[f]),c);
end;
done2:
if ss<>0 then begin
 s:=new_kern(ss); link(q):=s; link(s):=r;
 s:=link(q);
end;
while link(r)<>null do begin
 s:=r; r:=link(r); { unnecessary list traversal! }
end;
ss:=0;
if is_char_node(s) then begin
 f:=font(s); c:=character(s);
end else if type(s)=ligature_node then begin
 f:=font(lig_char(s)); c:=character(lig_char(s));
end else goto done3;
if (0<=margin_char[f])and(margin_char[f]<=255) then begin
 ss:=kerning(f,c,qi(margin_char[f]));
end;
done3:
if ss<>0 then begin
 link(s):=new_kern(ss);
 link(link(s)):=r;
end;
@z

@x
assign_font_int: begin n:=cur_chr; scan_font_ident; f:=cur_val;
 scan_optional_equals; scan_int;
 if n=0 then hyphen_char[f]:=cur_val@+else skew_char[f]:=cur_val;
 end;
@y
assign_font_int: begin n:=cur_chr; scan_font_ident; f:=cur_val;
 scan_optional_equals; scan_int;
 case n of
  0: hyphen_char[f]:=cur_val;
  1: skew_char[f]:=cur_val;
  othercases margin_char[f]:=cur_val;
 endcases;
 end;
@z

@x
primitive("skewchar",assign_font_int,1);
@!@:skew_char_}{\.{\\skewchar} primitive@>
@y
primitive("skewchar",assign_font_int,1);
@!@:skew_char_}{\.{\\skewchar} primitive@>
primitive("marginchar",assign_font_int,2);
@!@:margin_char_}{\.{\\marginchar} primitive@>
@z

@x
assign_font_int: if chr_code=0 then print_esc("hyphenchar")
 else print_esc("skewchar");
@y
assign_font_int: case chr_code of
 0: print_esc("hyphenchar");
 1: print_esc("skewchar");
 othercases print_esc("marginchar");
 endcases;
@z

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