FROM thTex.mp
point label definition
############################################################

vardef p_label@#(expr txt,pos,rot,mode) =
  if (mode=1) or (mode=7): interim labeloffset:=(u/8) fi;
  lab:=thelabel@#(txt, pos);
  if mode>1: pickup PenD fi;
  if mode=1:
    pickup pencircle scaled (u/6);
    drawdot(pos);
    process_label(pos,0);
  elseif mode=2: process_uplabel;       
  elseif mode=3: process_downlabel;
  elseif mode=4: process_updownlabel;
  elseif mode=5: process_circledlabel;
  elseif mode=6: process_boxedlabel;
  elseif mode=7: process_label(pos,rot);  % station name
  elseif mode=8: process_filledlabel(pos, rot);
  else: process_label(pos,rot); fi;
enddef;

FROM therion.mp
low level process_ various label types
############################################################

def fonts_setup (expr t,s,m,l,h) =
  write "\def\updown#1#2{\vbox{" &
        "\offinterlineskip" &
        "\setbox100=\hbox{#1}" &
        "\setbox101=\hbox{#2}" &
        "\ifnum\wd100>\wd101\hsize=\wd100\else\hsize=\wd101\fi" &
        "\centerline{\box100}\vskip4pt" &
        "\centerline{\box101}}}" &
        "\def\thlabel{\thnormalsize}" &
        "\def\thremark{\thsmallsize\si}" &
        "\def\thcomment{\thsmallsize}" &
        "\def\thentrance{\thsmallsize}" &
        "\def\thaltitude{\thsmallsize}" &
        "\def\thstationname{\thsmallsize}" &
        "\def\thdate{\thsmallsize}" &
        "\def\thheight{\thsmallsize}" &
        "\def\thheightpos{+\ignorespaces}" &
        "\def\thheightneg{-\ignorespaces}" &
        "\def\thframed{\thsmallsize}" &
        "\def\thwallaltitude{\thtinysize}"
  to "mptexpre.tex";
  write "\def\thtinysize{\size[" & decimal max(optical_zoom*t,0) & "]}" & 
        "\def\thsmallsize{\size[" & decimal max(optical_zoom*s,0) & "]}" & 
        "\def\thnormalsize{\size[" & decimal max(optical_zoom*m,0) & "]}" & 
        "\def\thlargesize{\size[" & decimal max(optical_zoom*l,0) & "]}" & 
        "\def\thhugesize{\size[" & decimal max(optical_zoom*h,0) & "]}" 
  to "mptexpre.tex";
  write EOF to "mptexpre.tex";
enddef;

% @MACRO
% process_label --
%
% draws a label saved in <I>lab</I> picture variable and calls 
% <A HREF="#write_bbox">write_bbox</A> macro.


def process_label (expr cent, rot) =
  begingroup;
    interim bboxmargin:=0.8bp;
    q:=((bbox lab) smoothed 2) rotatedaround (cent, rot);
    draw lab rotatedaround (cent, rot);
    write_circ_bbox(q);  % without corners smoothing it was enough to use
                         % write_bbox(q);
  endgroup;
enddef;

% @MACRO
% process_uplabel --
%
% draws a label into semicircular box and writes clipping path to a file

def process_uplabel =
  begingroup;
    interim bboxmargin := 0.8 bp;
    q:=bbox lab;
  endgroup;
    alef:=.8-.02*(xpart lrcorner q - xpart llcorner q);
%    show alef;
    q:=alef[llcorner q,ulcorner q]{up} .. {down}alef[lrcorner q, urcorner q] --
        lrcorner q -- llcorner q -- cycle;
    draw lab;
    draw q;
    q:=reverse q;
    write_circ_bbox(q);
enddef;

% @MACRO
% process_downlabel --
%
% draws a label into down oriented semicircular box and writes
% clipping path to a file

def process_downlabel =
  begingroup;
    interim bboxmargin := 0.8 bp;
    q:=bbox lab;
  endgroup;
    alef:=1-(.8-.02*(xpart lrcorner q - xpart llcorner q));
    q:=alef[llcorner q,ulcorner q]{down} .. 
        {up}alef[lrcorner q, urcorner q] --
        urcorner q -- ulcorner q -- cycle;
    draw lab;
    draw q;
    write_circ_bbox(q);
enddef;

% @MACRO
% process_updownlabel --
%
% draws a label splitted into down and up oriented semicircular boxes and 
% writes clipping path to a file

def process_updownlabel =
  begingroup;
    interim bboxmargin := 0.8 bp;
    p:=bbox lab;
  endgroup;
    leftside:=xpart llcorner p;
    rightside:=xpart lrcorner p;
    draw (xpart llcorner p,.5[ypart llcorner p,ypart ulcorner p]) -- 
         (xpart lrcorner p,.5[ypart llcorner p,ypart ulcorner p]);
    alef:=1.05-.02*(xpart lrcorner p - xpart llcorner p);
%    alef:=.8-.02*(rightside-leftside);
    p:=alef[(leftside, ypart llcorner p),(leftside, ypart ulcorner p)]{up} .. 
       {down}alef[(rightside, ypart lrcorner p), (rightside, ypart urcorner p)]
        -- alef[(rightside, ypart urcorner p), (rightside, ypart lrcorner p)]{down}
        .. {up}alef[(leftside, ypart ulcorner p),(leftside, ypart llcorner p)]
        -- cycle;
%    p:=alef[llcorner p,ulcorner p]{up} .. {down}alef[lrcorner p, urcorner p] --
%        aleff[llcorner p,ulcorner p]{down} .. 
%        {up}aleff[lrcorner p, urcorner p] -- cycle;
    draw lab;
    draw p;
    p:=reverse p;
    write_circ_bbox(p);
enddef;

def process_updownlabel_OLD =
    p:=bbox lab;
    q:=bbox Lab;
    leftside:=min(xpart llcorner p, xpart ulcorner q);
    rightside:=max(xpart lrcorner p, xpart urcorner q);
    draw .5[(leftside, ypart llcorner p),(leftside, ypart ulcorner q)] -- 
         .5[(rightside,ypart lrcorner p),(rightside,ypart urcorner q)];
    alef:=.8-.02*(rightside-leftside);
    q:=alef[(leftside, ypart llcorner p),(leftside, ypart ulcorner p)]{up} .. 
       {down}alef[(rightside, ypart lrcorner p), (rightside, ypart urcorner p)]
        -- alef[(rightside, ypart urcorner q), (rightside, ypart lrcorner q)]{down}
        .. {up}alef[(leftside, ypart ulcorner q),(leftside, ypart llcorner q)]
        -- cycle;
    draw lab;
    draw Lab;
    draw q;
    q:=reverse q;
    write_circ_bbox(q);
enddef;

% @MACRO
% process_boxedlabel --
%
% draws a label into circular box and writes
% clipping path to a file

def process_boxedlabel =
    q:=bbox lab;
    draw lab;
    draw q;
    write_bbox(q);
enddef;

% @MACRO
% process_circledlabel --
%
% draws a label into circular box and writes
% clipping path to a file

def process_circledlabel =
  begingroup;
    interim bboxmargin := 0.4 bp;
    q:=bbox lab;
  endgroup;
    q:=point 0 of q .. point 1 of q .. point 2 of q .. point 3 of q .. cycle;
    draw lab;
    draw q;
    write_circ_bbox(q);
enddef;


% @MACRO
% write_bbox --
%
% Arguments:
%   <I>path</I> variable -- rectangular bounding box of a label;
%   assumptions: path is cyclic, counterclockwise oriented, with four points,
%   composed from linear segments;
%   see general <A HREF="#write_circ_bbox">write_circ_bbox</A> macro
% Results:
%   one file per figure which uses labels with a clipping path in pseudo-pdf 
%   format

def write_bbox (expr q) =
    file_name := jobname & "." & decimal(charcode) & "bbox";
    for i:=4 downto 0:
        s  :=  decimal(roundone(xpart point i of q)) & " " 
             & decimal(roundone(ypart point i of q)) 
             & if i=4: " m " else: " l" fi;
        write s to file_name;
    endfor;
    last_write := charcode;
enddef;

% @MACRO
% write_circ_bbox --
%
% Arguments:
%   <I>path</I> variable, only assumption is that <I>path</I> is cyclic
%   and counterclockwise oriented.
% Results:
%   one file per figure which uses labels with a clipping path in pseudo-pdf 
%   format

def write_circ_bbox expr q =
    file_name := jobname & "." & decimal(charcode) & "bbox";
    tmp:=length q;
    s :=  decimal(roundone(xpart point tmp of q)) & " " 
             & decimal(roundone(ypart point tmp of q)) & " m";
    write s to file_name;
    for i:=tmp downto 1:
        s :=  decimal(roundone(xpart precontrol i of q)) & " " 
             & decimal(roundone(ypart precontrol i of q)) & " "
             & decimal(roundone(xpart postcontrol i-1 of q)) & " " 
             & decimal(roundone(ypart postcontrol i-1 of q)) & " "
             & decimal(roundone(xpart point i-1 of q)) & " " 
             & decimal(roundone(ypart point i-1 of q)) & " c";
        write s to file_name;
    endfor;
    last_write := charcode;
enddef;


FROM thpoint.cxx
C code for labels, including height
############################################################
...from line 242

    // if not found, try to set fathers properties  
    default:
      if (cod.id == TT_2DOBJ_CLIP) {
        switch (this->type) {
          case TT_POINT_TYPE_STATION_NAME:
          case TT_POINT_TYPE_LABEL:
          case TT_POINT_TYPE_REMARK:
          case TT_POINT_TYPE_DATE:
          case TT_POINT_TYPE_ALTITUDE:
          case TT_POINT_TYPE_HEIGHT:
          case TT_POINT_TYPE_DIMENSIONS:
          case TT_POINT_TYPE_MAP_CONNECTION:
          case TT_POINT_TYPE_PASSAGE_HEIGHT:
            ththrow(("-clip not valid with type %s", thmatch_string(this->type,thtt_point_types)))
            break;
        }
      }
      th2ddataobject::set(cod, args, argenc, indataline);
	

...from line 399 Sets postprocess_label (aka process_label aka mode) = -1 ie default mode = -1 when none of the label modes are applicable

...from line 457 Sets postprocess_label values for points label, remark and station-name
	
...from line 574  Deals with point height variants, and near the bottom of this snippet sets postprocess_label to 7

    case TT_POINT_TYPE_HEIGHT:
      if ((this->tags & (TT_POINT_TAG_HEIGHT_P |
          TT_POINT_TAG_HEIGHT_N | TT_POINT_TAG_HEIGHT_U)) != 0) {        

        switch (this->tags & (TT_POINT_TAG_HEIGHT_P |
        TT_POINT_TAG_HEIGHT_N | TT_POINT_TAG_HEIGHT_U)) {
          case TT_POINT_TAG_HEIGHT_P:
            macroid = SYMP_HEIGHT_POSITIVE;
            break;
          case TT_POINT_TAG_HEIGHT_N:
            macroid = SYMP_HEIGHT_NEGATIVE;
            break;
          case TT_POINT_TAG_HEIGHT_U:
            macroid = SYMP_HEIGHT_UNSIGNED;
            break;
          default:
            return(false);
        }
        
        omacroid = macroid;
        if (this->context >= 0) 
          macroid = this->context;
        if (!out->symset->is_assigned(macroid))
          return(false);
        if (out->file == NULL)
          return(true);

        out->symset->get_mp_macro(omacroid);
        out->symset->export_mp_symbol_options(out->file, omacroid);
        fprintf(out->file,"p_label%s(btex \\thheight ",thpoint_export_mp_align2mp(thdb2d_rotate_align(this->align, xrr)));
        out->layout->export_mptex_font_size(out->file, this, false);


        if ((this->tags & TT_POINT_TAG_HEIGHT_P) != 0)
          fprintf(out->file,"\\thheightpos ");
        else if ((this->tags & TT_POINT_TAG_HEIGHT_N) != 0)
          fprintf(out->file,"\\thheightneg ");

        if (!thisnan(this->xsize)) {
          //if (double(int(this->xsize)) != this->xsize)
          //  sprintf(buff,"%.1f",this->xsize);
          //else
          //  sprintf(buff,"%.0f",this->xsize);
          fprintf(out->file,"%s",utf2tex(out->layout->units.format_human_length(this->xsize)));
        }
        this->db->buff_enc.strcpy((this->tags & (TT_POINT_TAG_HEIGHT_PQ |
            TT_POINT_TAG_HEIGHT_NQ | TT_POINT_TAG_HEIGHT_UQ)) != 0 ? "?" : "" );
        fprintf(out->file,"%s etex,",utf2tex(this->db->buff_enc.get_buffer()));
        postprocess_label = 7;
      }
      postprocess = false;
      break;