# HG changeset patch
# User Rik <rik@octave.org>
# Date 1380053824 25200
# Node ID bddb9688e41c1daca054d3219e8ba20d494f99c8
# Parent  997b700b6ad448f4ce4c2db3ea5bce3f9aa6dee4
feather.m: Overhaul function for Matlab visual compatibility.

* scripts/plot/feather.m: Reduce length of arrowhead size to 0.20 of arrow
shaft.  Change arrow head angle with shaft from 45 to 30 degrees.  Use variable
'h' instead of 'retval' to match documentation.  Redo input validation.
Add %!error input validation tests.

diff --git a/scripts/plot/feather.m b/scripts/plot/feather.m
--- a/scripts/plot/feather.m
+++ b/scripts/plot/feather.m
@@ -48,54 +48,56 @@
 ## @seealso{plot, quiver, compass}
 ## @end deftypefn
 
-function retval = feather (varargin)
+function h = feather (varargin)
 
   [hax, varargin, nargin] = __plt_get_axis_arg__ ("feather", varargin{:});
 
-  arrowsize = 0.25;
+  if (nargin == 0 || nargin > 3)
+    print_usage ();
+  endif
 
-  if (nargin == 0)
-    print_usage ();
-  elseif (nargin == 1 || (nargin == 2 && ! isnumeric (varargin{2})))
-    ioff = 2;
+  if (nargin == 1 || (nargin == 2 && ! isnumeric (varargin{2})))
     z = varargin{1}(:).';
     u = real (z);
     v = imag (z);
-  elseif (nargin > 1 && isnumeric (varargin{2}))
+    have_line_spec = (nargin == 2);
+  elseif (nargin >= 2 && isnumeric (varargin{2}))
     ioff = 3;
     u = varargin{1}(:).';
     v = varargin{2}(:).';
+    have_line_spec = (nargin == 3);
+  else
+    print_usage ();
   endif
 
-  line_spec = "b-";
-  have_line_spec = false;
-  while (ioff <= nargin)
-    arg = varargin{ioff++};
-    if ((ischar (arg) || iscellstr (arg)) && ! have_line_spec)
-      [linespec, valid] = __pltopt__ ("feather", arg, false);
+  arrowsize = 0.20;
+  line_spec = "-b";
+
+  if (have_line_spec)
+    arg = varargin{end};
+    if (ischar (arg) || iscellstr (arg))
+      [~, valid] = __pltopt__ ("feather", arg, false);
       if (valid)
         line_spec = arg;
-        have_line_spec = false;
-        break;
       else
-        error ("feather: invalid linespec");
+        error ("feather: invalid linestyle STYLE");
       endif
     else
-      error ("feather: unrecognized argument");
+      error ("feather: invalid linestyle STYLE");
     endif
-  endwhile
+  endif
 
   ## Matlab draws feather plots, with the arrow head as one continous
-  ## line, and each arrow separately. This is completely different than
+  ## line, and each arrow separately. This is completely different from
   ## quiver and quite ugly.
   n = length (u);
   xend = [1 : n] + u;
   xtmp = [1 : n] + u .* (1 - arrowsize);
   yend = v;
   ytmp = v .* (1 - arrowsize);
-  x = [[1 : n]; xend; xtmp  - v * arrowsize; xend; ...
-       xtmp + v * arrowsize];
-  y = [zeros(1, n); yend; ytmp  + u * arrowsize / 3; yend; ...
+  x = [[1 : n]; xend; xtmp - v * arrowsize / 3; xend; ...
+       xtmp + v * arrowsize / 3];
+  y = [zeros(1, n); yend; ytmp + u * arrowsize / 3; yend; ...
        ytmp - u * arrowsize / 3];
 
   oldfig = [];
@@ -112,7 +114,7 @@
   end_unwind_protect
 
   if (nargout > 0)
-    retval = hlist;
+    h = hlist;
   endif
 
 endfunction
@@ -125,3 +127,10 @@
 %! axis tight;
 %! title ('feather plot');
 
+%% Test input validation
+%!error feather ()
+%!error feather (1,2,3,4)
+%!error feather (1, "-r", 2)
+%!error <invalid linestyle STYLE> feather (1, "abc")
+%!error <invalid linestyle STYLE> feather (1, {1})
+