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##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
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## -*- texinfo -*-
## @deftypefn {} {[@var{h}, @var{fail}] =} __patch__ (@var{p}, @dots{})
## Undocumented internal function.
## @end deftypefn

## __patch__ (p, x, y, c)
## Create patch object from x and y with color c and parent p.
## Return handle to patch object.

function [h, failed] = __patch__ (p, varargin)

  h = NaN;
  failed = false;

  is_numeric_arg = cellfun (@isnumeric, varargin);

  if (isempty (varargin))
    args = varargin;
  elseif (is_numeric_arg(1))
    if (nargin < 3 || ! is_numeric_arg(2))
      failed = true;
    else
      if (nargin > 4 && all (is_numeric_arg(1:4)))
        x = varargin{1};
        y = varargin{2};
        z = varargin{3};
        c = varargin{4};
        iarg = 5;
      elseif (nargin > 3 && all (is_numeric_arg(1:3)))
        x = varargin{1};
        y = varargin{2};
        if (nargin > 4 && iscolorspec (varargin{4}))
          z = varargin{3};
          c = varargin{4};
          iarg = 5;
        else
          z = [];
          c = varargin{3};
          iarg = 4;
        endif
      elseif (nargin > 2 && all (is_numeric_arg(1:2)))
        x = varargin{1};
        y = varargin{2};
        z = [];
        if (iscolorspec (varargin{3}))
          c = varargin{3};
          iarg = 4;
        else
          c = [];
          iarg = 3;
        endif
      endif

      if (isvector (x))
        x = x(:);
        y = y(:);
        z = z(:);
        if (isnumeric (c))
          if (isvector (c) && numel (c) == numel (x))
            c = c(:);
          elseif (rows (c) != numel (x) && columns (c) == numel (x))
            c = c.';
          endif
        endif
      endif
      args{1} = "xdata";
      args{2} = x;
      args{3} = "ydata";
      args{4} = y;
      args{5} = "zdata";
      args{6} = z;

      if (isnumeric (c))

        if (ndims (c) == 3 && columns (c) == 1)
          c = permute (c, [1, 3, 2]);
        endif

        if (isvector (c) && numel (c) == columns (x))
          if (isnan (c))
            args{7} = "facecolor";
            args{8} = [1, 1, 1];
            args{9} = "cdata";
            args{10} = c;
          elseif (isnumeric (c))
            args{7} = "facecolor";
            args{8} = "flat";
            args{9} = "cdata";
            args{10} = c;
          else
            error ("patch: color data C must be numeric");
          endif
        elseif (isrow (c) && numel (c) == 3)
          args{7} = "facecolor";
          args{8} = c;
          args{9} = "cdata";
          args{10} = [];
        elseif (ndims (c) == 3 && size (c, 3) == 3)
          ## CDATA is specified as RGB data
          if ((rows (c) == 1 && columns (c) == 1) ...
              || (rows (c) == 1 && columns (c) == columns (x)))
            ## Single patch color or per-face color
            args{7} = "facecolor";
            args{8} = "flat";
            args{9} = "cdata";
            args{10} = c;
          elseif (rows (c) == rows (x) && columns (c) == columns (x))
            ## Per-vertex color
            args{7} = "facecolor";
            args{8} = "interp";
            args{9} = "cdata";
            args{10} = c;
          else
            error ("patch: Invalid TrueColor data C");
          endif
        else
          ## Color Vectors
          if (isempty (c))
            args{7} = "facecolor";
            args{8} = "interp";
            args{9} = "cdata";
            args{10} = [];
          elseif (size_equal (c, x) && size_equal (c, y))
            args{7} = "facecolor";
            args{8} = "interp";
            args{9} = "cdata";
            args{10} = c;
          else
            error ("patch: size of X, Y, and C must be equal");
          endif
        endif
      elseif (iscolorspec (c))
        args{7} = "facecolor";
        args{8} = tolower (c);
        args{9} = "cdata";
        args{10} = [];
      else
        args{7} = "facecolor";
        args{8} = [0, 0, 0];
        args{9} = "cdata";
        args{10} = [];
      endif

      args = [args, varargin(iarg:end)];
    endif
  else
    args = varargin;
  endif

  if (! failed)
    h = __go_patch__ (p, args{:});
  endif

endfunction

function retval = iscolorspec (arg)
  retval = false;
  if (ischar (arg))
    persistent colors = {"y", "yellow", "r", "red", "m", "magenta", ...
                         "c", "cyan", "g", "green", "b", "blue", ...
                         "w", "white", "k", "black"};
    if (any (strcmpi (arg, colors)))
      retval = true;
    endif
  endif
endfunction