# HG changeset patch
# User Rik <rik@octave.org>
# Date 1380053810 25200
# Node ID 576cf0589c6d312b9693ae2888dfa3b9bfd2efd7
# Parent  710b3d5fe9666c0469be166f737a81f3b3fa140f
Overhaul contour labeling functions.

* scripts/plot/clabel.m: Use 'h', rather than 'retval', to match variables to
documentation.  Improve performance of input processing by using try/catch block
and eliminating for loops.

* scripts/plot/private/__clabel__.m: Get X and Y spacing in points from axis
rather than assuming 4"x3" plot figure.  Fix incorrect determination of axis limits
if no contour handle provided.  Rename loop vars i1, j1 to i,j.  Performance
improvement by using bsxfun over repmat.  Use find to replace while loop (slow).
Keep label rotation in the range [-90, 90] for readability.

diff --git a/scripts/plot/clabel.m b/scripts/plot/clabel.m
--- a/scripts/plot/clabel.m
+++ b/scripts/plot/clabel.m
@@ -61,11 +61,11 @@
 ## @seealso{contour, contourf, contour3, meshc, surfc, text}
 ## @end deftypefn
 
-function retval = clabel (c, varargin)
+function h = clabel (c, varargin)
 
-  label_spacing = 2 * 72;
   have_hg = false;
   have_labelspacing = false;
+  label_spacing = 144;  # 2 inches in points
 
   if (nargin < 1)
     print_usage ();
@@ -75,12 +75,13 @@
     arg = varargin{1};
     if (isscalar (arg) && ishandle (arg)
         && strcmp (get (arg, "type"), "hggroup"))
-      obj = get (arg);
-      if (! isfield (obj, "contourmatrix"))
-        error ("clabel: expecting the handle to be a contour group");
-      endif
+      try
+        get (arg, "contourmatrix");
+      catch
+        error ("clabel: H must be a handle to a contour group");
+      end_try_catch
+      have_hg = true;
       hg = arg;
-      have_hg = true;
       varargin(1) = [];
     else
       hparent = gca ();
@@ -94,44 +95,43 @@
     v = [];
   endif
 
-  for i = 1 : length (varargin) - 1
-    arg = varargin{i};
-    if (strcmpi (arg, "labelspacing"))
-      label_spacing = varargin{i+1};
-      have_labelspacing = true;
-      varargin(i:i+1) = [];
-      break;
-    endif
-  endfor
+  idx = strcmpi (varargin(1:2:end), "manual");
+  if (any (idx))
+    error ('clabel: "manual" contour mode is not supported');
+  endif
 
-  for i = 1 : length (varargin)
-    arg = varargin{i};
-    if (strcmpi (arg, "manual"))
-      error ("clabel: manual contouring mode not supported");
-    endif
-  endfor
+  idx = find (strcmpi (varargin(1:2:end), "labelspacing"), 1);
+  if (! isempty (idx))
+    have_labelspacing = true;
+    label_spacing = varargin{2*idx};
+    varargin(2*idx+(-1:0)) = [];
+  endif    
 
   if (have_hg)
     if (! isempty (v))
       if (have_labelspacing)
         set (hg, "textlistmode", "manual", "textlist", v,
-             "labelspacing", label_spacing, "showtext", "on");
+                 "labelspacing", label_spacing, "showtext", "on");
       else
         set (hg, "textlistmode", "manual", "textlist", v, "showtext", "on");
       endif
     else
       if (have_labelspacing)
-        set (hg,"showtext", "on", "labelspacing", label_spacing);
+        set (hg, "showtext", "on", "labelspacing", label_spacing);
       else
-        set (hg,"showtext", "on");
+        set (hg, "showtext", "on");
       endif
     endif
-    retval = findobj (hg, "type", "text");
+    htmp = findobj (hg, "type", "text");
     if (! isempty (varargin))
-      set (retval, varargin {:});
+      set (htmp, varargin{:});
     endif
   else
-    retval =  __clabel__ (c, v, hparent, label_spacing, [], varargin{:});
+    htmp =  __clabel__ (c, v, hparent, label_spacing, [], varargin{:});
+  endif
+
+  if (nargout > 0)
+    h = htmp;
   endif
 
 endfunction
diff --git a/scripts/plot/private/__clabel__.m b/scripts/plot/private/__clabel__.m
--- a/scripts/plot/private/__clabel__.m
+++ b/scripts/plot/private/__clabel__.m
@@ -23,11 +23,14 @@
 
 function h = __clabel__ (c, v, hparent, label_spacing, z, varargin)
 
-  ## FIXME: Why assume?  Can get position in points directly from axis.
-  ## Assume that the plot size is 4 by 3 inches.
+  hax = ancestor (hparent, "axes");
+  units = get (hax, "units");
+  set (hax, "units", "points");
+  axpos = get (hax, "position");
+  set (hax, "units", units);
   lims = axis ();
-  xspacing = 72 * 4 / abs (lims(1) - lims(2));
-  yspacing = 72 * 3 / abs (lims(3) - lims(4));
+  xspacing = axpos(3) / (lims(2) - lims (1));
+  yspacing = axpos(4) / (lims(4) - lims (3));
 
   if (isscalar (hparent) && ishandle (hparent)
       && strcmp (get (hparent, "type"), "hggroup"))
@@ -38,80 +41,89 @@
     ymin = min (y(:));
     ymax = max (y(:));
   else
-    i1 = 1;
-    while (i1 < length (c))
-      clev = c(1,i1);
-      clen = c(2,i1);
-      p = c(:, i1+1:i1+clen);
+    xmin = xmax = ymin = ymax = NaN;
+    i = 1;
+    while (i < length (c))
+      clen = c(2,i);
+      data = c(:, i+(1:clen));
 
-      xmin = min (c(1,:));
-      xmax = max (c(1,:));
-      ymin = min (c(2,:));
-      ymax = max (c(2,:));
+      xmin = min ([xmin, data(1,:)]);
+      xmax = max ([xmax, data(1,:)]);
+      ymin = min ([ymin, data(2,:)]);
+      ymax = max ([ymax, data(2,:)]);
 
-      i1 += clen+1;
+      i += clen+1;
     endwhile
   endif
 
   ## Decode contourc output format and place labels.
-  i1 = 1;
   h = [];
-  while (i1 < length (c))
-    clev = c(1,i1);
-    clen = c(2,i1);
+  i = 1;
+  while (i < length (c))
+    clev = c(1,i);
+    clen = c(2,i);
 
-    if (!isempty (v) && ! any (find (clev == v)))
-      i1 += clen+1;
+    if (! isempty (v) && ! any (v == clev))
+      i += clen+1;
       continue;
     endif
 
-    p = c(:, i1+1:i1+clen) .* repmat ([xspacing; yspacing], 1, clen);
+    p = bsxfun (@times, c(:, i+(1:clen)), [xspacing; yspacing]);
     d = sqrt (sumsq (diff (p, 1, 2)));
     cumd = cumsum (d);
-    td = sum (d);
+    td = cumd(end);
     ntag = ceil (td / label_spacing);
 
-    if (all (c(:,i1+1) == c(:,i1+clen)))
-      Spacing = td / ntag;
-      pos = Spacing / 2 + [0:ntag-1] * Spacing;
+    if (all (c(:,i+1) == c(:,i+clen)))
+      ## Closed contour
+      ## FIXME: This spreads the tags uniformly around the contour which
+      ## looks nice, but it does not respect the label_spacing attribute.
+      ## Should we follow user input, which can result in two labels being
+      ## quite close to each other?
+      spacing = td / ntag;
+      pos = spacing/2 + spacing*[0:ntag-1];
     else
+      ## Open contour
       pos = zeros (1, ntag);
-      pos(1) = (td - label_spacing * (ntag - 1)) ./ 2;
-      pos(2:ntag) = pos(1) + [1:ntag-1] * label_spacing;
+      pos(1) = (td - label_spacing*(ntag - 1)) / 2;
+      pos(2:ntag) = pos(1) + label_spacing*[1:ntag-1];
     endif
 
-    j1 = 2;
-    tlabel = sprintf ("%g", clev);
-    for i = 1 : ntag
-      tagpos = pos(i);
+    tlabel = sprintf ("%.5g", clev);
+
+    for tagpos = pos
 
-      while (j1 < clen && cumd(j1) < tagpos)
-        j1++;
-      endwhile
-      tpos = sum (c(:,i1+j1-1:i1+j1), 2) ./ 2;
+      j = find (cumd > tagpos, 1);
+      if (isempty (j))
+        j = clen;
+      endif
+      tpos = sum (c(:,i+j-1:i+j), 2) / 2;
 
       if (   tpos(1) != xmin && tpos(1) != xmax
           && tpos(2) != ymin && tpos(2) != ymax)
-        trot = 180 / pi * atan2 (diff (c(2,i1+j1-1:i1+j1)),
-                                 diff (c(1,i1+j1-1:i1+j1)));
-
+        trot = 180 / pi * atan2 (diff (c(2,i+j-1:i+j)),
+                                 diff (c(1,i+j-1:i+j)));
+        if (abs (trot) > 90)
+          trot += 180;
+        endif
         if (ischar (z))
           ht = text (tpos(1), tpos(2), clev, tlabel, "rotation", trot,
-                     "parent", hparent, "horizontalalignment", "center",
-                     "userdata", clev, varargin{:});
-        elseif (!isempty (z))
+                     "horizontalalignment", "center", "userdata", clev,
+                     "parent", hparent, varargin{:});
+        elseif (! isempty (z))
           ht = text (tpos(1), tpos(2), z, tlabel, "rotation", trot,
-                     "parent", hparent, "horizontalalignment", "center",
-                     "userdata", clev, varargin{:});
+                     "horizontalalignment", "center", "userdata", clev,
+                     "parent", hparent, varargin{:});
         else
           ht = text (tpos(1), tpos(2), tlabel, "rotation", trot,
-                     "parent", hparent, "horizontalalignment", "center",
-                     "userdata", clev, varargin{:});
+                     "horizontalalignment", "center", "userdata", clev,
+                     "parent", hparent, varargin{:});
         endif
         h = [h; ht];
       endif
     endfor
-    i1 += clen+1;
+    i += clen+1;
   endwhile
+
 endfunction