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##
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## distribution or <https://octave.org/copyright/>.
##
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########################################################################

## -*- texinfo -*-
## @deftypefn  {} {} view (@var{azimuth}, @var{elevation})
## @deftypefnx {} {} view ([@var{azimuth} @var{elevation}])
## @deftypefnx {} {} view ([@var{x} @var{y} @var{z}])
## @deftypefnx {} {} view (2)
## @deftypefnx {} {} view (3)
## @deftypefnx {} {} view (@var{hax}, @dots{})
## @deftypefnx {} {[@var{azimuth}, @var{elevation}] =} view ()
## Query or set the viewpoint for the current axes.
##
## The parameters @var{azimuth} and @var{elevation} can be given as two
## arguments or as 2-element vector.  The viewpoint can also be specified with
## Cartesian coordinates @var{x}, @var{y}, and @var{z}.
##
## The call @code{view (2)} sets the viewpoint to
## @w{@var{azimuth} = 0}@ and @w{@var{elevation} = 90}, which is the default
## for 2-D graphs.
##
## The call @code{view (3)} sets the viewpoint to
## @w{@var{azimuth} = -37.5}@ and @w{@var{elevation} = 30}, which is the
## default for 3-D graphs.
##
## If the first argument @var{hax} is an axes handle, then operate on
## this axes rather than the current axes returned by @code{gca}.
##
## If no inputs are given, return the current @var{azimuth} and
## @var{elevation}.
## @end deftypefn

function [azimuth, elevation] = view (varargin)

  [hax, varargin, nargin] = __plt_get_axis_arg__ ("view", varargin{:});

  if (nargin > 2)
    print_usage ();
  endif

  if (nargout > 0 && nargin > 0)
    error ("view: cannot simultaneously get and set viewpoint");
  endif

  if (isempty (hax))
    hax = gca ();
  endif

  if (nargin == 0)
    vw = get (hax, "view");
    az = vw(1);
    el = vw(2);
  elseif (numel (varargin) == 1)
    x = varargin{1};
    if (numel (x) == 2)
      az = x(1);
      el = x(2);
    elseif (numel (x) == 3)
      if (x(2) == 0)
        ## special case for negative 0
        [az, el] = cart2sph (x(2), x(1), x(3));

        if (x(1) == 0)
          ## Matlab Compatibility: Force +0 azimuth instead of +/-0 or
          ## +/-180deg azimuth for z-aligned vector.
          az = 0;
        endif

      else
        [az, el] = cart2sph (-x(2), x(1), x(3));
      endif
      az *= 180/pi;
      el *= 180/pi;
    elseif (x == 2)
      az = 0;
      el = 90;
    elseif (x == 3)
      az = -37.5;
      el = 30;
    else
      print_usage ();
    endif
  elseif (numel (varargin) == 2)
    az = varargin{1};
    el = varargin{2};
  endif

  if (nargin > 0)
    set (hax, "view", [az, el]);
  else
    if (nargout == 1)
      azimuth = [az, el];
    elseif (nargout == 2)
      azimuth = az;
      elevation = el;
    endif
  endif

endfunction


%!test
%! hf = figure ("visible", "off");
%! unwind_protect
%!   plot3 ([0,1], [0,1], [0,1]);
%!   [az, el] = view ();
%!   assert ([az, el], [-37.5, 30], eps);
%!   view (2);
%!   [az, el] = view ();
%!   assert ([az, el], [0, 90], eps);
%!   view ([1 1 0]);
%!   [az, el] = view ();
%!   assert ([az, el], [135, 0], eps);
%! unwind_protect_cleanup
%!   close (hf);
%! end_unwind_protect

%!test
%! hf = figure ("visible", "off");
%! unwind_protect
%!   line ();
%!   [az, el] = view ();
%!   assert ([az, el], [0, 90], eps);
%!   view (3);
%!   [az, el] = view ();
%!   assert ([az, el], [-37.5, 30], eps);
%! unwind_protect_cleanup
%!   close (hf);
%! end_unwind_protect

%!test <*57800>
%! hf = figure ("visible", "off");
%! unwind_protect
%!   plot3 ([0,1], [0,1], [0,1]);
%!   view ([0, 0, 1]);
%!   [az, el] = view ();
%!   assert ([az, el], [0, 90], eps);
%! unwind_protect_cleanup
%!   close (hf);
%! end_unwind_protect

%!test <*65641>
%! hf = figure ("visible", "off");
%! unwind_protect
%!   plot3 ([0,1], [0,1], [0,1]);
%!   view ([1, 0, 0]);
%!   [az, el] = view ();
%!   assert ([az, el], [90, 0], eps);
%!   view ([-1, 0, 0]);
%!   [az, el] = view ();
%!   assert ([az, el], [-90, 0], eps);
%!   view ([0, 1, 0]);
%!   [az, el] = view ();
%!   assert ([az, el], [180, 0], eps);
%!   view ([0, -1, 0]);
%!   [az, el] = view ();
%!   assert ([az, el], [0, 0], eps);
%!   view ([0, 0, 1]);
%!   [az, el] = view ();
%!   assert ([az, el], [0, 90], eps);
%!   view ([0, 0, -1]);
%!   [az, el] = view ();
%!   assert ([az, el], [0, -90], eps);
%!   view ([1, 0.001, 0]);
%!   [az, el] = view ();
%!   assert ([az, el], [90 + 0.001*180/pi, 0], eps ("single"));
%! unwind_protect_cleanup
%!   close (hf);
%! end_unwind_protect

%!test <*65641> # Verify compatible z-vector viewpoint.
%! hf = figure ("visible", "off");
%! unwind_protect
%!   ml_out = [0, 90, Inf] .* ones (8, 1);
%!   ml_out(1:2:end-1, 2) = -90;
%!   output = NaN (8, 3);
%!   plot3 ([0,1], [0,1], [0,1]);
%!   idx = 1;
%!   for x1 = [-0, 0]
%!     for x2 = [-0, 0]
%!       for x3 = [-1, 1]
%!         view ([x1, x2, x3]);
%!         [az, el] = view ();
%!         output(idx, :) = [az, el, 1/az];
%!         idx++;
%!       endfor
%!     endfor
%!   endfor
%!   assert (isequaln (output, ml_out));
%! unwind_protect_cleanup
%!   close (hf);
%! end_unwind_protect


## Test input validation
%!error <Invalid call> view (0, 0, 1)
%!error <cannot simultaneously get and set> [a, b] = view ([1, 1, 1])
