Account for varargin being a struct

When called from places like optmagstr, varargin is actually a struct.
Also, the struct contains many other additional parameters to do with
fitting, so before calling genmagstr in optmagstr,
warning('off','sw_readparam:UnreadInput') is called. This stops
sw_readparam from issuing warnings. This also stops the
`spinw:genmagstr:UnreadInput` warning from being triggered, which
is why its name has been changed to UnreadInput, to avoid ugly
unecessary warnings.

+sw_tests/+unit_tests/unittest_spinw_genmagstr.m

@@ -46,8 +46,8 @@
              {'n', [0 1 1], 'mode', 'direct', 'S', [1; 0; 0]}, ...
              {'mode', 'tile', 'k', [0 0 1/2], 'n', [0 0 1], 'S', [1; 0; 0]}, ...
              {'mode', 'helical', 'k', [0 0 1/3], 'S', [1; 0; 0;], 'x0', []}, ...
-             {'mode', 'func', 'x0', [pi/2 -pi/4 0 0 [0 0 1/3] pi pi/2], 'unit', 'lu'}, ...
-             {'mode', 'fourier', 'S',[1; i; 0], 'n', [1 0 0]}
+             {'mode', 'func', 'x0', [pi/2 -pi/4 0 0 [0 0 1/3] pi pi/2], 'unit', 'lu', 'next', [1 2 1]}, ...
+             {'mode', 'fourier', 'S', [1; i; 0], 'n', [1 0 0]}
              };
          complex_n_input = {[1 1+i 0], [i 0 0]};
          rotate_phi_inputs = {{'phi', pi/4}, {'phid', 45}, {'phi', pi/4, 'phid', 90}};
@@ -110,15 +110,15 @@ function test_tile_too_few_S_raises_error(testCase)
         function test_ignored_input_warns(testCase, ignored_inputs)
             testCase.verifyWarning(...
                 @() testCase.swobj.genmagstr(ignored_inputs{:}), ...
-                'spinw:genmagstr:UnusedInput')
+                'spinw:genmagstr:UnreadInput')
         end
         function test_rotate_ignored_input_warns(testCase)
             swobj = copy(testCase.swobj);
             % Need to initialise structure before rotating it
             swobj.genmagstr('mode', 'direct', 'S', [1; 0; 0]);
             testCase.verifyWarning(...
                 @() swobj.genmagstr('mode', 'rotate', 'k', [0 0 1/3]), ...
-                'spinw:genmagstr:UnusedInput')
+                'spinw:genmagstr:UnreadInput')
         end
         function test_helical_spin_size_incomm_with_nExt_warns(testCase)
             swobj = copy(testCase.swobj);

swfiles/@spinw/genmagstr.m

@@ -230,10 +230,16 @@ function genmagstr(obj, varargin)
 % Error if S or k is provided but is empty. This means it has failed the
 % input validation, but hasn't caused an error because soft=True
 err_str = [];
-if any(strcmp(varargin, 'S')) && isempty(param.S)
+if isstruct(varargin{1})
+    varargin_struct = varargin{1};
+else
+    varargin_struct = struct(varargin{:});
+end
+varargin_names = fields(varargin_struct);
+if any(strcmpi(varargin_names, 'S')) && isempty(param.S)
     err_str = ["S"];
 end
-if any(strcmp(varargin, 'k')) && isempty(param.k)
+if any(strcmpi(varargin_names, 'k')) && isempty(param.k)
     err_str = [err_str "k"];
 end
 if length(err_str) > 0
@@ -286,13 +292,13 @@ function genmagstr(obj, varargin)
 if ~any(strcmp(fields(mode_args), param.mode))
     error('spinw:genmagstr:WrongMode','Wrong param.mode value!');
 else
-    input_arg_names = varargin(1:2:end);
-    input_arg_names(ismember(input_arg_names, ["mode" "norm"])) = [];
-    unused_args = setdiff(input_arg_names, mode_args.(param.mode));
+    unused_args = {varargin_names{:}};
+    unused_args(ismember(lower(unused_args), ["mode" "norm"])) = [];
+    unused_args(ismember(lower(unused_args), lower(mode_args.(lower(param.mode))))) = [];
     if ~isempty(unused_args)
-        warning('spinw:genmagstr:UnusedInput', ...
+        warning('spinw:genmagstr:UnreadInput', ...
                 'Input(s) %s will be ignored in %s mode', ...
-                join(unused_args, ', '), param.mode)
+                string(join(unused_args', ', ')), param.mode)
     end
 end