function spm_ovhelper_3Dreg(cmd, varargin)
% Helper function to register spm_orthviews plugins via spm_XYZreg
% FORMAT spm_ovhelper_3Dreg('register', h, V)
% Register a (3D) graphics with the main spm_orthviews display. This will
% draw 3D crosshairs at the current spm_orthviews position and update
% them whenever the spm_orthviews cursor moves.
% h - a graphics handle or a tag of graphics handle to register
% V - a volume handle (or equivalent) containing dimensions and
%     voxel-to-world mapping information
%
% FORMAT spm_ovhelper_3Dreg('unregister', h)
% h - a graphics handle or a tag of graphics handle to unregister
%
% FORMAT spm_ovhelper_3Dreg('setcoords', xyz, h)
% Update position of crosshairs in 3D display
% xyz - new crosshair coordinates (in mm)
% h - a graphics handle or a tag of graphics handle to update
%
% FORMAT spm_ovhelper_3Dreg('xhairson', h)
% FORMAT spm_ovhelper_3Dreg('xhairsoff', h)
% Toggle display of crosshairs in 3D display.
% h - a graphics handle or a tag of graphics handle 
%__________________________________________________________________________
% Copyright (C) 2008-2013 Wellcome Trust Centre for Neuroimaging

% Volkmar Glauche
% $Id: spm_ovhelper_3Dreg.m 5219 2013-01-29 17:07:07Z spm $

if ishandle(varargin{1})
    h = varargin{1};
elseif ischar(varargin{1})
    h = findobj(0, 'Tag',varargin{1});
    if ~ishandle(h)
        warning([mfilename ':InvalidHandle'], ...
            'No valid graphics handle found');
        return;
    else
        h = get(h(ishandle(h)),'parent');
    end
end

switch lower(cmd)
    case 'register'
        register(h,varargin{2:end});
        return;
    case 'setcoords'
        setcoords(varargin{1:end});
        return;
    case 'unregister',
        unregister(h,varargin{2:end});
        return;
    case 'xhairson'
        xhairs(h,'on',varargin{2:end});
        return;
    case 'xhairsoff'
        xhairs(h,'off',varargin{2:end});
        return;
end

%==========================================================================
function register(h,V,varargin)
try
    global st;
    if isstruct(st)
        xyz=spm_orthviews('pos');
        if isfield(st,'registry')
            hreg = st.registry.hReg;
        else
            [hreg,xyz]=spm_XYZreg('InitReg', h, V.mat, ...
                V.dim(1:3)',xyz);
            spm_orthviews('register',hreg);
        end
        spm_XYZreg('Add2Reg',hreg,h,mfilename);
        feval(mfilename,'setcoords',xyz,h);
        set(h, 'DeleteFcn', ...
            sprintf('%s(''unregister'',%f);', mfilename, h));
    end
catch
    warning([mfilename ':XYZreg'],...
        'Unable to register to spm_orthviews display');
    disp(lasterror);
end

%==========================================================================
function setcoords(xyz,h,varargin)
spm('pointer','watch');
Xh = findobj(h,'Tag', 'Xhairs');
if ishandle(Xh)
    vis = get(Xh(1),'Visible');
    delete(Xh);
else
    vis = 'on';
end
axes(findobj(h,'Type','axes'));
lim = axis;
Xh = line([xyz(1), xyz(1), lim(1);...
       xyz(1), xyz(1), lim(2)],...
      [lim(3), xyz(2), xyz(2);...
       lim(4), xyz(2), xyz(2)],...
      [xyz(3), lim(5), xyz(3);...
       xyz(3), lim(6), xyz(3)],...
      'Color','b', 'Tag','Xhairs', 'Visible',vis,...
      'Linewidth',2, 'HitTest','off');
spm('pointer','arrow');

%==========================================================================
function xhairs(h,val,varargin)
Xh = findobj(h, 'Tag', 'Xhairs');
if ~isempty(Xh)
    set(Xh,'Visible',val);
end

%==========================================================================
function unregister(h,varargin)
try
    global st;
    if isfield(st,'registry')
        hreg = st.registry.hReg;
    else
        hreg = findobj(0,'Tag','hReg');
    end
    if h == hreg
        spm_XYZreg('UnInitReg',hreg);
        st = rmfield(st, 'registry');
    else
        spm_XYZreg('Del2Reg',hreg,h);
    end
catch
    warning([mfilename ':XYZreg'],...
        'Unable to unregister');
    disp(lasterror);
end