function varargout = snapnow(varargin)

%SNAPNOW Force a snapshot of output.

%   SNAPNOW forces checking for figure and system changes when inside

%   publishing, and acts as a DRAWNOW otherwise.

%   DATA = SNAPNOW('get') returns the persistent data which is generated

%   and used during publishing.

%

%   SNAPNOW('set', DATA) sets this persistent data.  If empty, it is

%   assumed that publishing is exiting.  Otherwise it is assumed that

%   publishing is commencing, and other initializations to this data occur.

%

%   F = SNAPNOW('beginCell', iCell, ...) indicates that the cell iCell is

%   being entered during publishing.  SNAPNOW returns false, for its use in

%   conditional breakpoints.

%

%   F = SNAPNOW('endCell', iCell, ...) indicates that the cell iCell is

%   being left.  Again, SNAPNOW returns false, for its use in conditional

%   breakpoints.

%

%   These two forms may be combined:

%

%      snapnow('endCell', 2, 'beginCell', 3)

%

%   such as occurs on a cell-to-cell boundary.

% Matthew J. Simoneau, October 2006

% Copyright 2006-2011 The MathWorks, Inc.

persistent data 

persistent cellStack 

% Return false to continue execution.

if (nargout == 1) 

    varargout = {false}; 

end 

% Because publishing behaves so badly when there is an error in a

% conditional breakpoint (which there shouldn't be), put this all in a

% try-catch.

try 

    % Parse inputs.

    if nargin > 0 

        switch varargin{1} 

            case 'get' 

                varargout = {data};

            case 'set' 

                cellStack = [];

                data = varargin{2};

                if isempty(data)

                    % Leaving publishing.

                    munlock;

                    data = [];

                else

                    % Initializing publishing.

                    mlock;

                    data.counter = makeCounter(0);

                    data.pictureList = {};

                    data.placeList = [];

                    data.options.filenameGenerator = makeFilenameGenerator(data.baseImageName);

                    % Systems.

                    data.plugins(1).check = @hasSimulink;

                    data.plugins(1).classname = 'internal.matlab.publish.PublishSimulinkSystems';

                    data.plugins(1).instance = [];

                    % Figures.

                    data.plugins(2).check = @true;

                    data.plugins(2).classname = 'internal.matlab.publish.PublishFigures';

                    data.plugins(2).instance = [];

                    % This gives us a placement for files with parse errors.

                    data.lastGo = 1;

                end

            case 'append' 

                % Undocumented prototype code for creating animated GIFs.

                %

                % SNAPNOW is being called to createa an animation.

                %

                % For example: snapnow('append')

                if isempty(data)

                    % Running normally, outside the context of publishing.

                    if (nargin > 1)

                        pause(varargin{2})

                    end

                    drawnow

                else

                    % Inside the context of publishing.

                    if (nargin > 1)

                        data.append = varargin{2};

                    else

                        data.append = Inf;

                    end

                    iCell = cellStack(end);

                    data = leavingCell(iCell, data, true);

                    data = enteringCell(iCell, data, false);

                    data = rmfield(data,'append');

                end                

            otherwise 

                % SNAPNOW is being called in a conditional breakpoint at a

                % cell boundary.  Pairs of arguments are processed in turn.

                %

                % For example: snapnow('endCell', 2, 'beginCell', 3);

                % Assume odd inputs are either beginCell or endCell.

                exiting = strcmp(varargin(1:2:end), 'endCell'); 

                iCell = [varargin{2:2:end}]; 

                % We've exited the file, perhaps prematurely.

                iCell(iCell < 0) = data.lastGo; 

                % Short-circuit when this is a redundancy.

                % That is, when entering a cell that is alreay on the stack.

                % or leaving a cell that is not on the stack.

                toRemove = xor(ismember(iCell, cellStack), exiting); 

                exiting(toRemove) = []; 

                iCell(toRemove) = []; 

                % Do a capture/compare on only the first "beginCell" or

                % "endCell".  Subsequent cases would recapture the same info.

                doCapture = false(size(iCell)); 

                doCapture(1) = true; 

                % Take the appropriate action for each pair.

                for k = 1:numel(iCell) 

                    if exiting(k) 

                        cellStack(cellStack == iCell(k)) = []; 

                        data = leavingCell(iCell(k), data, doCapture(k)); 

                    else 

                        cellStack(end + 1) = iCell(k); %#ok<AGROW> 

                        data = enteringCell(iCell(k), data, doCapture(k)); 

                    end 

                end 

        end 

    else

        % Called directly with no arguments from user code.

        if isempty(data)

            % Running normally, outside the context of publishing.

            drawnow

        else

            % Inside the context of publishing.

            iCell = cellStack(end);

            data = leavingCell(iCell, data, true);

            data = enteringCell(iCell, data, false);

        end

    end 

catch e

    % Something went wrong in the publishing infrastructure.

    disp(getReport(e))

end

end