beta 2011.10.20 11:44

2 files changed, 202 insertions, 146 deletions

diff --git a/metapost/context/base/mp-char.mpiv b/metapost/context/base/mp-char.mpiv
index 83fa20155..91d50b912 100644
--- a/metapost/context/base/mp-char.mpiv
+++ b/metapost/context/base/mp-char.mpiv
@@ -11,7 +11,10 @@
 %C therefore copyrighted by \PRAGMA. See licen-en.pdf for
 %C details.
 
-%D This is ancient code .. but I see no need to rewrite it.
+%D This is ancient code .. but I see no need to rewrite it. This is
+%D already a partial rewrite but more could be delegated to \LUA\
+%D when used in \CONTEXT\ but it does not pay off now to look into
+%D that.
 
 if unknown context_shap : input "mp-shap.mpiv" ; fi ;
 if   known context_flow : endinput ; fi ;
@@ -119,38 +122,41 @@ def flow_new_chart =
 
     flow_dash_pattern           := nullpicture ;
 
-    numeric flow_xypoint       ; flow_xypoint := 0 ;
-    numeric flow_cpath         ; flow_cpath   := 0 ;
-
-    pair    flow_xypoints []   ;
-    boolean flow_xyfree   [][] ;
-    path    flow_xypath   [][] ;
-    numeric flow_xysx     [][] ;
-    numeric flow_xysy     [][] ;
-    color   flow_xyfill   [][] ;
-    color   flow_xydraw   [][] ;
-    numeric flow_xyline   [][] ;
-    boolean flow_xypeep   [][] ;
-    picture flow_xytext   [][] ;
-    picture flow_xylabel_l[][] ;
-    picture flow_xylabel_r[][] ;
-    picture flow_xylabel_t[][] ;
-    picture flow_xylabel_b[][] ;
-    picture flow_xyexit_l [][] ;
-    picture flow_xyexit_r [][] ;
-    picture flow_xyexit_t [][] ;
-    picture flow_xyexit_b [][] ;
-    path    flow_cpaths   []   ;
-    numeric flow_cline    []   ;
-    color   flow_ccolor   []   ;
-    boolean flow_carrow   []   ;
-    boolean flow_cdash    []   ;
-    boolean flow_ccross   []   ;
-
-    picture flow_tpicture[][]  ;
-    picture flow_bpicture[][]  ;
-    picture flow_lpicture[][]  ;
-    picture flow_rpicture[][]  ;
+    numeric flow_xypoint   ; flow_xypoint   := 0 ;
+    numeric flow_cpath     ; flow_cpath     := 0 ;
+
+    pair    flow_xypoints   []   ;
+    boolean flow_xyfree     [][] ;
+    path    flow_xypath     [][] ;
+    numeric flow_xysx       [][] ;
+    numeric flow_xysy       [][] ;
+    color   flow_xyfill     [][] ;
+    color   flow_xydraw     [][] ;
+    numeric flow_xyline     [][] ;
+    boolean flow_xypeep     [][] ;
+    picture flow_xytext     [][] ;
+    picture flow_xylabel_l  [][] ;
+    picture flow_xylabel_r  [][] ;
+    picture flow_xylabel_t  [][] ;
+    picture flow_xylabel_b  [][] ;
+    picture flow_xyexit_l   [][] ;
+    picture flow_xyexit_r   [][] ;
+    picture flow_xyexit_t   [][] ;
+    picture flow_xyexit_b   [][] ;
+    picture flow_xycomment_txt[][][][] ;
+    string  flow_xycomment_loc[][][][] ;
+    numeric flow_xycomment_len[][][][] ;
+    path    flow_cpaths     [] ;
+    numeric flow_cline      [] ;
+    color   flow_ccolor     [] ;
+    boolean flow_carrow     [] ;
+    boolean flow_cdash      [] ;
+    boolean flow_ccross     [] ;
+    picture flow_tpicture   [][] ;
+    picture flow_bpicture   [][] ;
+    picture flow_lpicture   [][] ;
+    picture flow_rpicture   [][] ;
+    path    flow_centers    [][][] ;
 
     predefined_shapes[61] := (fullcircle scaled (1.5*predefined_shapes_yradius) xscaled (flow_grid_height/flow_grid_width)) ;
     predefined_shapes[62] := (fullcircle scaled (2.0*predefined_shapes_yradius) xscaled (flow_grid_height/flow_grid_width)) ;
@@ -160,11 +166,11 @@ enddef ;
 flow_new_chart ;
 
 def flow_y_pos(expr y) =
-    if flow_reverse_y :
+%     if flow_reverse_y :
         flow_max_y + 1 - y
-    else :
-        y
-    fi
+%     else :
+%         y
+%     fi
 enddef ;
 
 def flow_initialize_grid(expr maxx, maxy) =
@@ -381,17 +387,22 @@ vardef flow_connection_path =
     flow_xypoints[flow_xypoint])
 enddef ;
 
-def flow_draw_connection =
+def flow_draw_connection(expr i,xfrom,yfrom,xto,yto) = % 'i' is a comment reference
     if flow_xypoint > 0 :
         flow_collapse_points ;
         flow_trim_points ;
-        flow_cpath := flow_cpath + 1 ;
+        flow_cpath := flow_cpath + 1 ; % maybe also store as x,y
         flow_cpaths[flow_cpath] := flow_connection_path flow_scaled_to_grid ;
         flow_cline[flow_cpath]  := flow_connection_line_width ;
         flow_ccolor[flow_cpath] := flow_connection_line_color ;
         flow_carrow[flow_cpath] := flow_arrowtip ;
         flow_cdash[flow_cpath]  := flow_dashline ;
         flow_ccross[flow_cpath] := flow_showcrossing ;
+        if flow_reverse_connection :
+            flow_centers[xto]  [yto]  [i] := flow_cpaths[flow_cpath] ;
+        else :
+            flow_centers[xfrom][yfrom][i] := flow_cpaths[flow_cpath] ;
+        fi ;
     else :
         message("no connection defined") ;
     fi ;
@@ -450,46 +461,85 @@ def flow_draw_midpoint (expr n) =
     endgroup ;
 enddef ;
 
-def flow_flush_picture(expr x, yy) =
-    begingroup ; save y ; numeric y ;
+def flow_flush_picture(expr x, yy) = % more in lua
+    begingroup ;
+    save y ; numeric y ;
     y := flow_y_pos(yy) ;
-    if known flow_xytext[x][y] :
+    if known flow_xytext[x][y] : % maybe test on path for comments
         begingroup ;
             % flow_xypath[x][y]
             save p, offset ; path p ; pair offset ;
             offset := flow_xy_offset((x+0.5)*flow_grid_width,(flow_max_y-y+1.5)*flow_grid_height) ;
             offset := offset shifted (-flow_xyline[x][y]/4,-flow_xyline[x][y]/4) ; % terrible hack (some compensation)
-            p := fullsquare
-                xscaled flow_grid_width
-                yscaled flow_grid_height
-                shifted offset ;
-            if known flow_xytext[x][y]:
-                draw flow_xytext[x][y] shifted offset ;
+            p := fullsquare xscaled flow_grid_width yscaled flow_grid_height shifted offset ;
+            %
+            save loc ; string  loc ;
+            save len ; numeric len ;
+            save txt ; picture txt ;
+            save cen ; path    cen ;
+            %
+            txt := flow_xytext[x][y] ; if known txt :
+                draw txt shifted offset ;
             fi ;
-            if known flow_xylabel_t[x][y] :
-                label.urt(flow_xylabel_t[x][y],0.5[ulcorner p,urcorner p]) ;
+            % is simple comment (sort of obsolete)
+            txt := flow_xylabel_t[x][y] ; if known txt :
+                label.urt(txt,0.5[ulcorner p,urcorner p]) ;
             fi ;
-            if known flow_xylabel_b[x][y] :
-                label.lrt(flow_xylabel_b[x][y],0.5[llcorner p,lrcorner p]) ;
+            txt := flow_xylabel_b[x][y] ; if known txt :
+                label.lrt(txt,0.5[llcorner p,lrcorner p]) ;
             fi ;
-            if known flow_xylabel_l[x][y] :
-                label.ulft(flow_xylabel_l[x][y],0.5[ulcorner p,llcorner p]) ;
+            txt := flow_xylabel_l[x][y] ; if known txt :
+                label.ulft(txt,0.5[ulcorner p,llcorner p]) ;
             fi ;
-            if known flow_xylabel_r[x][y] :
-                label.urt (flow_xylabel_r[x][y],0.5[urcorner p,lrcorner p]) ;
+            txt := flow_xylabel_r[x][y] ; if known txt :
+                label.urt (txt,0.5[urcorner p,lrcorner p]) ;
             fi ;
-            if known flow_xyexit_t[x][y] :
-                label.top(flow_xyexit_t[x][y],0.5[ulcorner p,urcorner p] shifted (0, flow_grid_height/2)) ;
+            % is shifted comment
+            txt := flow_xyexit_t[x][y] ; if known txt :
+                label.top(txt,0.5[ulcorner p,urcorner p] shifted (0, flow_grid_height/2)) ;
             fi ;
-            if known flow_xyexit_b[x][y] :
-                label.bot(flow_xyexit_b[x][y],0.5[llcorner p,lrcorner p] shifted (0,-flow_grid_height/2)) ;
+            txt := flow_xyexit_b[x][y] ; if known txt :
+                label.bot(txt,0.5[llcorner p,lrcorner p] shifted (0,-flow_grid_height/2)) ;
             fi ;
-            if known flow_xyexit_l[x][y] :
-                label.lft(flow_xyexit_l[x][y],0.5[ulcorner p,llcorner p] shifted (-flow_grid_width/2,0)) ;
+            txt := flow_xyexit_l[x][y] ; if known txt :
+                label.lft(txt,0.5[ulcorner p,llcorner p] shifted (-flow_grid_width/2,0)) ;
             fi ;
-            if known flow_xyexit_r[x][y] :
-                label.rt (flow_xyexit_r[x][y],0.5[urcorner p,lrcorner p] shifted ( flow_grid_width/2,0)) ;
+            txt := flow_xyexit_r[x][y] ; if known txt :
+                label.rt (txt,0.5[urcorner p,lrcorner p] shifted ( flow_grid_width/2,0)) ;
             fi ;
+            % along the path or anchored
+            for i=1 upto infinity :
+                cen := flow_centers[x][y][i] ;
+                if unknown cen :
+                    break ;
+                else :
+                    for j=1 upto infinity :
+                        txt := flow_xycomment_txt[x][y][i][j] ;
+                        if unknown txt :
+                            break ;
+                        else : % todo: see how we can store suffix
+                            loc := flow_xycomment_loc[x][y][i][j] ;
+                            len := flow_xycomment_len[x][y][i][j] ;
+                            pair a ;
+                            if len <> 0 :
+                                a := point len along cen ;
+                            fi ;
+                            if     loc = "tl" : label.ulft(txt,if len = 0 : 0.5[ulcorner p,urcorner p] else : a fi) ;
+                            elseif loc = "t"  : label.top (txt,if len = 0 : 0.5[ulcorner p,urcorner p] else : a fi) ;
+                            elseif loc = "tr" : label.urt (txt,if len = 0 : 0.5[ulcorner p,urcorner p] else : a fi) ;
+                            elseif loc = "bl" : label.llft(txt,if len = 0 : 0.5[llcorner p,lrcorner p] else : a fi) ;
+                            elseif loc = "b"  : label.bot (txt,if len = 0 : 0.5[llcorner p,lrcorner p] else : a fi) ;
+                            elseif loc = "br" : label.lrt (txt,if len = 0 : 0.5[llcorner p,lrcorner p] else : a fi) ;
+                            elseif loc = "lt" : label.ulft(txt,if len = 0 : 0.5[ulcorner p,llcorner p] else : a fi) ;
+                            elseif loc = "l"  : label.lft (txt,if len = 0 : 0.5[ulcorner p,llcorner p] else : a fi) ;
+                            elseif loc = "lb" : label.lrt (txt,if len = 0 : 0.5[ulcorner p,llcorner p] else : a fi) ;
+                            elseif loc = "rt" : label.urt (txt,if len = 0 : 0.5[urcorner p,lrcorner p] else : a fi) ;
+                            elseif loc = "r"  : label.rt  (txt,if len = 0 : 0.5[urcorner p,lrcorner p] else : a fi) ;
+                            elseif loc = "rb" : label.lrt (txt,if len = 0 : 0.5[urcorner p,lrcorner p] else : a fi) ; fi ;
+                        fi ;
+                    endfor ;
+                fi ;
+            endfor ;
         endgroup ;
     fi ;
     endgroup ;
@@ -499,15 +549,21 @@ def flow_chart_draw_text(expr x, y, p) =
     flow_xytext[x][y] := p ;
 enddef ;
 
-def flow_chart_draw_label_t(expr x, y, p) = flow_xylabel_t[x][y] := p ; enddef ;
-def flow_chart_draw_label_b(expr x, y, p) = flow_xylabel_b[x][y] := p ; enddef ;
-def flow_chart_draw_label_l(expr x, y, p) = flow_xylabel_l[x][y] := p ; enddef ;
-def flow_chart_draw_label_r(expr x, y, p) = flow_xylabel_r[x][y] := p ; enddef ;
+def flow_chart_draw_label_t   (expr x, y, p) = flow_xylabel_t  [x][y] := p ; enddef ;
+def flow_chart_draw_label_b   (expr x, y, p) = flow_xylabel_b  [x][y] := p ; enddef ;
+def flow_chart_draw_label_l   (expr x, y, p) = flow_xylabel_l  [x][y] := p ; enddef ;
+def flow_chart_draw_label_r   (expr x, y, p) = flow_xylabel_r  [x][y] := p ; enddef ;
 
-def flow_chart_draw_exit_t (expr x, y, p) = flow_xyexit_t [x][y] := p ; enddef ;
-def flow_chart_draw_exit_b (expr x, y, p) = flow_xyexit_b [x][y] := p ; enddef ;
-def flow_chart_draw_exit_l (expr x, y, p) = flow_xyexit_l [x][y] := p ; enddef ;
-def flow_chart_draw_exit_r (expr x, y, p) = flow_xyexit_r [x][y] := p ; enddef ;
+def flow_chart_draw_exit_t    (expr x, y, p) = flow_xyexit_t   [x][y] := p ; enddef ;
+def flow_chart_draw_exit_b    (expr x, y, p) = flow_xyexit_b   [x][y] := p ; enddef ;
+def flow_chart_draw_exit_l    (expr x, y, p) = flow_xyexit_l   [x][y] := p ; enddef ;
+def flow_chart_draw_exit_r    (expr x, y, p) = flow_xyexit_r   [x][y] := p ; enddef ;
+
+def flow_chart_draw_comment (expr x, y, i, j, p, l, n) =
+    flow_xycomment_txt[x][y][i][j] := p ;
+    flow_xycomment_loc[x][y][i][j] := l ;
+    flow_xycomment_len[x][y][i][j] := n ;
+enddef ;
 
 boolean flow_reverse_connection ; flow_reverse_connection := false ;
 
@@ -613,7 +669,7 @@ vardef flow_valid_connection (expr xfrom, yfrom, xto, yto) =
     endgroup
 enddef ;
 
-def flow_connect_top_bottom (expr xfrom, yyfrom, zfrom) (expr xto, yyto, zto) =
+def flow_connect_top_bottom (expr n) (expr xfrom, yyfrom, zfrom) (expr xto, yyto, zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,6) :
@@ -638,11 +694,11 @@ def flow_connect_top_bottom (expr xfrom, yyfrom, zfrom) (expr xto, yyto, zto) =
             flow_xypoints[5] := flow_xypoints[5] shifted (0,flow_dsp_y) ;
         fi
         %%%% end experiment
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_left_right (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_left_right (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,6) :
@@ -662,11 +718,11 @@ def flow_connect_left_right (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
             flow_xypoints[4] := flow_xypoints[4] shifted (0,-flow_dsp_y) ;
         fi ;
         %%%% end experiment
-        flow_draw_connection ;
-  fi ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
+    fi ;
 enddef ;
 
-def flow_connect_left_top (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_left_top (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,5) :
@@ -678,11 +734,11 @@ def flow_connect_left_top (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
         if not flow_valid_connection(xfrom,yfrom,xto,yto) :
             flow_xypoints[3] := flow_xy_on_grid(2,4) ;
         fi ;
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_left_bottom (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_left_bottom (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,5) :
@@ -694,11 +750,11 @@ def flow_connect_left_bottom (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
         if not flow_valid_connection(xfrom,yfrom,xto,yto) :
             flow_xypoints[3] := flow_xy_on_grid(2,4) ;
         fi ;
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_right_top (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_right_top (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,5) :
@@ -710,11 +766,11 @@ def flow_connect_right_top (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
         if not flow_valid_connection(xfrom,yfrom,xto,yto) :
             flow_xypoints[3] := flow_xy_on_grid(2,4) ;
         fi ;
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_right_bottom (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_right_bottom (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,5) :
@@ -737,11 +793,11 @@ def flow_connect_right_bottom (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
           flow_xypoints[4] := flow_xypoints[4] shifted (0,flow_dsp_y) ;
         fi
         %%%% end experiment
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_left_left (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_left_left (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,6) :
@@ -755,11 +811,11 @@ def flow_connect_left_left (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
             flow_xypoints[3] := flow_y_on_grid(2,yfrom,yto,zfrom) ;
             flow_xypoints[4] := flow_xy_on_grid(5,3) ;
         fi ;
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_right_right (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_right_right (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,6) :
@@ -773,11 +829,11 @@ def flow_connect_right_right (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
           flow_xypoints[3] := flow_y_on_grid(2,yfrom,yto,zfrom) ;
           flow_xypoints[4] := flow_xy_on_grid(5,3) ;
         fi ;
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_top_top (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_top_top (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,6) :
@@ -799,11 +855,11 @@ def flow_connect_top_top (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
             flow_xypoints[5] := flow_xypoints[5] shifted (0,flow_dsp_y) ;
         fi ;
         %%%% end experiment
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_bottom_bottom (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
+def flow_connect_bottom_bottom (expr n) (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
     yfrom := flow_y_pos(yyfrom) ;
     yto := flow_y_pos(yyto) ;
     if flow_points_initialized(xfrom,yfrom,xto,yto,6) :
@@ -828,38 +884,38 @@ def flow_connect_bottom_bottom (expr xfrom,yyfrom,zfrom) (expr xto,yyto,zto) =
             flow_xypoints[5] := flow_xypoints[5] shifted (0,flow_dsp_y) ;
         fi
         %%%% end experiment
-        flow_draw_connection ;
+        flow_draw_connection(n,xfrom,yyfrom,xto,yyto) ;
     fi ;
 enddef ;
 
-def flow_connect_bottom_top (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
+def flow_connect_bottom_top (expr n) (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
     flow_reverse_connection := true ;
-    flow_connect_top_bottom (xto,yto,zto) (xfrom,yfrom,zfrom) ;
+    flow_connect_top_bottom (n) (xto,yto,zto) (xfrom,yfrom,zfrom) ;
 enddef ;
 
-def flow_connect_right_left (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
+def flow_connect_right_left (expr n) (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
     flow_reverse_connection := true ;
-    flow_connect_left_right (xto,yto,zto) (xfrom,yfrom,zfrom) ;
+    flow_connect_left_right (n) (xto,yto,zto) (xfrom,yfrom,zfrom) ;
 enddef ;
 
-def flow_connect_top_left (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
+def flow_connect_top_left (expr n) (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
     flow_reverse_connection := true ;
-    flow_connect_left_top(xto,yto,zto) (xfrom,yfrom,zfrom) ;
+    flow_connect_left_top (n) (xto,yto,zto) (xfrom,yfrom,zfrom) ;
 enddef ;
 
-def flow_connect_bottom_left (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
+def flow_connect_bottom_left (expr n) (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
     flow_reverse_connection := true ;
-    flow_connect_left_bottom (xto,yto,zto) (xfrom,yfrom,zfrom) ;
+    flow_connect_left_bottom (n) (xto,yto,zto) (xfrom,yfrom,zfrom) ;
 enddef ;
 
-def flow_connect_top_right (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
+def flow_connect_top_right (expr n) (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
     flow_reverse_connection := true ;
-    flow_connect_right_top (xto,yto,zto) (xfrom,yfrom,zfrom) ;
+    flow_connect_right_top (n) (xto,yto,zto) (xfrom,yfrom,zfrom) ;
 enddef ;
 
-def flow_connect_bottom_right (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
+def flow_connect_bottom_right (expr n) (expr xfrom,yfrom,zfrom) (expr xto,yto,zto) =
     flow_reverse_connection := true ;
-    flow_connect_right_bottom (xto,yto,zto) (xfrom,yfrom,zfrom) ;
+    flow_connect_right_bottom (n) (xto,yto,zto) (xfrom,yfrom,zfrom) ;
 enddef ;
 
 def flow_draw_test_shape(expr x, y) =
@@ -895,55 +951,55 @@ def flow_show_connection(expr n, m) =
         flow_draw_test_shape(6,2) ; flow_draw_test_shape(4,6) ;
 
         if     (m=1) :
-            flow_connect_top_bottom (2,2,0) (4,5,0) ;
-            flow_connect_top_bottom (3,3,0) (5,1,0) ;
-            flow_connect_top_bottom (2,5,0) (1,3,0) ;
-            flow_connect_top_bottom (6,2,0) (4,6,0) ;
+            flow_connect_top_bottom    (0) (2,2,0) (4,5,0) ;
+            flow_connect_top_bottom    (0) (3,3,0) (5,1,0) ;
+            flow_connect_top_bottom    (0) (2,5,0) (1,3,0) ;
+            flow_connect_top_bottom    (0) (6,2,0) (4,6,0) ;
         elseif (m=2) :
-            flow_connect_top_top (2,2,0) (4,5,0) ;
-            flow_connect_top_top (3,3,0) (5,1,0) ;
-            flow_connect_top_top (2,5,0) (1,3,0) ;
-            flow_connect_top_top (6,2,0) (4,6,0) ;
+            flow_connect_top_top       (0) (2,2,0) (4,5,0) ;
+            flow_connect_top_top       (0) (3,3,0) (5,1,0) ;
+            flow_connect_top_top       (0) (2,5,0) (1,3,0) ;
+            flow_connect_top_top       (0) (6,2,0) (4,6,0) ;
         elseif (m=3) :
-            flow_connect_bottom_bottom (2,2,0) (4,5,0) ;
-            flow_connect_bottom_bottom (3,3,0) (5,1,0) ;
-            flow_connect_bottom_bottom (2,5,0) (1,3,0) ;
-            flow_connect_bottom_bottom (6,2,0) (4,6,0) ;
+            flow_connect_bottom_bottom (0) (2,2,0) (4,5,0) ;
+            flow_connect_bottom_bottom (0) (3,3,0) (5,1,0) ;
+            flow_connect_bottom_bottom (0) (2,5,0) (1,3,0) ;
+            flow_connect_bottom_bottom (0) (6,2,0) (4,6,0) ;
         elseif (m=4) :
-            flow_connect_left_right (2,2,0) (4,5,0) ;
-            flow_connect_left_right (3,3,0) (5,1,0) ;
-            flow_connect_left_right (2,5,0) (1,3,0) ;
-            flow_connect_left_right (6,2,0) (4,6,0) ;
+            flow_connect_left_right    (0) (2,2,0) (4,5,0) ;
+            flow_connect_left_right    (0) (3,3,0) (5,1,0) ;
+            flow_connect_left_right    (0) (2,5,0) (1,3,0) ;
+            flow_connect_left_right    (0) (6,2,0) (4,6,0) ;
         elseif (m=5) :
-            flow_connect_left_left (2,2,0) (4,5,0) ;
-            flow_connect_left_left (3,3,0) (5,1,0) ;
-            flow_connect_left_left (2,5,0) (1,3,0) ;
-            flow_connect_left_left (6,2,0) (4,6,0) ;
+            flow_connect_left_left     (0) (2,2,0) (4,5,0) ;
+            flow_connect_left_left     (0) (3,3,0) (5,1,0) ;
+            flow_connect_left_left     (0) (2,5,0) (1,3,0) ;
+            flow_connect_left_left     (0) (6,2,0) (4,6,0) ;
         elseif (m=6) :
-            flow_connect_right_right (2,2,0) (4,5,0) ;
-            flow_connect_right_right (3,3,0) (5,1,0) ;
-            flow_connect_right_right (2,5,0) (1,3,0) ;
-            flow_connect_right_right (6,2,0) (4,6,0) ;
+            flow_connect_right_right   (0) (2,2,0) (4,5,0) ;
+            flow_connect_right_right   (0) (3,3,0) (5,1,0) ;
+            flow_connect_right_right   (0) (2,5,0) (1,3,0) ;
+            flow_connect_right_right   (0) (6,2,0) (4,6,0) ;
         elseif (m=7) :
-            flow_connect_left_top (2,2,0) (4,5,0) ;
-            flow_connect_left_top (3,3,0) (5,1,0) ;
-            flow_connect_left_top (2,5,0) (1,3,0) ;
-            flow_connect_left_top (6,2,0) (4,6,0) ;
+            flow_connect_left_top      (0) (2,2,0) (4,5,0) ;
+            flow_connect_left_top      (0) (3,3,0) (5,1,0) ;
+            flow_connect_left_top      (0) (2,5,0) (1,3,0) ;
+            flow_connect_left_top      (0) (6,2,0) (4,6,0) ;
         elseif (m=8) :
-            flow_connect_left_bottom (2,2,0) (4,5,0) ;
-            flow_connect_left_bottom (3,3,0) (5,1,0) ;
-            flow_connect_left_bottom (2,5,0) (1,3,0) ;
-            flow_connect_left_bottom (6,2,0) (4,6,0) ;
+            flow_connect_left_bottom   (0) (2,2,0) (4,5,0) ;
+            flow_connect_left_bottom   (0) (3,3,0) (5,1,0) ;
+            flow_connect_left_bottom   (0) (2,5,0) (1,3,0) ;
+            flow_connect_left_bottom   (0) (6,2,0) (4,6,0) ;
         elseif (m=9) :
-            flow_connect_right_top (2,2,0) (4,5,0) ;
-            flow_connect_right_top (3,3,0) (5,1,0) ;
-            flow_connect_right_top (2,5,0) (1,3,0) ;
-            flow_connect_right_top (6,2,0) (4,6,0) ;
+            flow_connect_right_top     (0) (2,2,0) (4,5,0) ;
+            flow_connect_right_top     (0) (3,3,0) (5,1,0) ;
+            flow_connect_right_top     (0) (2,5,0) (1,3,0) ;
+            flow_connect_right_top     (0) (6,2,0) (4,6,0) ;
         else :
-            flow_connect_right_bottom (2,2,0) (4,5,0) ;
-            flow_connect_right_bottom (3,3,0) (5,1,0) ;
-            flow_connect_right_bottom (2,5,0) (1,3,0) ;
-            flow_connect_right_bottom (6,2,0) (4,6,0) ;
+            flow_connect_right_bottom  (0) (2,2,0) (4,5,0) ;
+            flow_connect_right_bottom  (0) (3,3,0) (5,1,0) ;
+            flow_connect_right_bottom  (0) (2,5,0) (1,3,0) ;
+            flow_connect_right_bottom  (0) (6,2,0) (4,6,0) ;
         fi ;
 
     flow_end_chart ;
diff --git a/metapost/context/base/mp-tool.mpiv b/metapost/context/base/mp-tool.mpiv
index 79110e752..65a76f8fa 100644
--- a/metapost/context/base/mp-tool.mpiv
+++ b/metapost/context/base/mp-tool.mpiv
@@ -1190,7 +1190,7 @@ primarydef pct along pat = % also negative
 enddef ;
 
 primarydef len on pat =
-    (arctime if len>0 : len else : (arclength(pat)+len) fi of pat) of pat
+    ((arctime if len>0 : len else : (arclength(pat)+len) fi of pat) of pat)
 enddef ;
 
 % this cuts of a piece from both ends