function gbprop(action);
%GBPROP Demonstrates the propagation of Gaussian Beams.

%	Victor Jones, 3-5-98

% For reference purposes here is a list of storage locations:
%	set(gcf,'UserData',[tasAxes lasAxes]) - i.e. pair of axes handles
%	set(tasAxes,'UserData',cntlHndl) - i.e. array of uicontro handles
%	set(lasAxes,'UserData',[z; q]) - i.e. a position-q value array
%	set(0,'UserData',region)
%	set(cntlHndl(1),'Value','current region')
%	set(cntlHndl(2),'Value','current region')
%	set(cntlHndl(3),'UserData',plotHndl)
%	set(cntlHndl(8),'Value',device spec)
%	set(cntlHndl(10),''Value'',b) where b is the button of origin
%	set(cntlHndl(10),'String','last entered value')
%	set(cntlHndl(10),'UserData','position of beam minimum');
%	set(cntlHndl(12),'String','last entered value')
%	set(cntlHndl(12),'UserData','Fresnel length');
%	set(cntlHndl(14),'String','last entered value')
%	set(cntlHndl(14),'UserData','beam wavelength');


if nargin<1,
    action='initialize';

end;

%===================================
if strcmp(action,'initialize'),

	set(0,'UserData',[]);
	% Definition of transverse axes space
	tasTop = 0.98;
	tasBottom = 0.35;
	tasLeft = 0.02;
	tasRight = 0.65;
	tasPos = [tasLeft tasBottom tasRight-tasLeft tasTop-tasBottom];
	% Definition of longitudinal axes space
	lasTop = tasBottom - 0.04;
	lasBottom = 0;
	lasLeft = tasLeft;
	lasRight = 1.0;
	lasPos = [lasLeft lasBottom lasRight-lasLeft lasTop-lasBottom];
	% Create a figure with two axes objects
	figNumber = figure( ... 
		'Name','Gaussian Beam Demo', ...
		'NumberTitle','off', ...
		'Color',[0.9 0.9 0.9],...
		'Units','normal',...
		'Position',[0.15 0.15 0.75 0.75],...
		'Visible','off');
	tasAxes = subplot('Position',tasPos);
	set(tasAxes,...	
		'Box','on',...
		'Units','normalized', ...
		'NextPlot','add',...
		'XTick',[],'YTick',[],'ZTick',[], ...
		'Visible','on');
	lasAxes = subplot('Position',lasPos);
	set(lasAxes,...
		'Box','on',...
		'Units','normalized',...
		'Color',[0 0 0],...
		'NextPlot','add',...
		'XTick',[],'YTick',[],'ZTick',[],...
		'Visible','on');
	set(gcf,'UserData',[tasAxes lasAxes])
	% Definition of data entry space
	desTop = tasTop;
	desBottom = tasBottom;
	desLeft = tasRight + 0.02;
	desRight = lasRight;
	desPos = [desLeft desBottom desRight-desLeft desTop-desBottom];
	frmBorder = 0.015;
	cntlTop = desTop - frmBorder;
	cntlWid = 0.14; cntlHt = 0.08; cntlSpacing = 0.02;
	% Create a frame for the data entry space
	set(gcf,'CurrentAxes',tasAxes);
	frmHndl = uicontrol( ...
		'Style','frame', ...
		'Units','normalized', ...
		'Position',desPos, ...
		'BackgroundColor',[0.5 0.5 0.5]);

	%====================================
	% Create the "Initialize beam" control button
	cntlNumber = 1;
	yPos = cntlTop-(round(cntlNumber./2)-1)*(cntlHt+cntlSpacing);
	if rem(cntlNumber,2) == 0
		xPos = desRight - frmBorder - cntlWid;
	else
		xPos = desLeft + frmBorder;
	end
	labelStr = 'Initialize beam';
	callbackStr = [...
 		'axes = get(gcf,''UserData'');',...
 		'cntlHndl = get(axes(1),''UserData'');',...
		'set(cntlHndl(1),''Value'',1),',...
 		'set(cntlHndl(10),''Value'',1);',...
 		'gbprop(''get info_1'')'];

	cntlPos = [xPos yPos-cntlHt cntlWid cntlHt];
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','pushbutton', ...
		'Units','normalized', ...
		'String',labelStr, ...
		'Position',cntlPos, ...
		'Callback',callbackStr);

	%====================================
	% Create the "Add device" control button
	cntlNumber = 2;
	yPos = cntlTop-(round(cntlNumber./2)-1)*(cntlHt+cntlSpacing);
	if rem(cntlNumber,2) == 0
		xPos = desRight - frmBorder - cntlWid;
	else
		xPos = desLeft + frmBorder;
	end
	labelStr = 'Add device';
	callbackStr = [...
 		'axes = get(gcf,''UserData'');',...
 		'cntlHndl = get(axes(1),''UserData'');',...
		'set(cntlHndl(1),''Value'',1),',...
 		'set(cntlHndl(10),''Value'',2);',...
		'gbprop(''get device'');'];

	cntlPos = [xPos yPos-cntlHt cntlWid cntlHt];
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','pushbutton', ...
		'Units','normalized', ...
		'String',labelStr, ...
		'Position',cntlPos, ...
		'Callback',callbackStr);

	%====================================
	% Create the "Launch beam" control button
	cntlNumber = 3;
	yPos = cntlTop-(round(cntlNumber./2)-1)*(cntlHt+cntlSpacing);
	if rem(cntlNumber,2) == 0
		xPos = desRight - frmBorder - cntlWid;
	else
		xPos = desLeft + frmBorder;
	end
	labelStr = 'Launch again';
     callbackStr = [...
		'axes = get(gcf,''UserData'');',...
 		'cntlHndl = get(axes(1),''UserData'');',...
		'set(cntlHndl(1),''Value'',1),',...
 		'set(cntlHndl(10),''Value'',3);',...
 		'gbprop(''las plot'')'];

	cntlPos = [xPos yPos-cntlHt cntlWid cntlHt];
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','pushbutton', ...
		'Units','normalized', ...
		'String',labelStr, ...
		'Position',cntlPos, ...
		'Callback',callbackStr);

	%====================================
	% Create an "Remove device" control button
	cntlNumber = 4;
	yPos = cntlTop-(round(cntlNumber./2)-1)*(cntlHt+cntlSpacing);
	if rem(cntlNumber,2) == 0
		xPos = desRight - frmBorder - cntlWid;
	else
		xPos = desLeft + frmBorder;
	end
	labelStr = 'Remove device';
	callbackStr = [...
		'axes = get(gcf,''UserData'');',...
 		'cntlHndl = get(axes(1),''UserData'');',...
 		'set(cntlHndl(10),''Value'',4);',...
		'set(gcf,''WindowButtonDownFcn'',''gbprop(''''kill device'''')'');'];

	cntlPos = [xPos yPos-cntlHt cntlWid cntlHt];
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','pushbutton', ...
		'Units','normalized', ...
		'String',labelStr, ...
		'Position',cntlPos, ...
		'Callback',callbackStr);

	%====================================
	% Create an "Profile beam" control button
	cntlNumber = 5;
	yPos = cntlTop-(round(cntlNumber./2)-1)*(cntlHt+cntlSpacing);
	if rem(cntlNumber,2) == 0
		xPos = desRight - frmBorder - cntlWid;
	else
		xPos = desLeft + frmBorder;
	end
	labelStr = 'Profile beam';
     callbackStr = [...
		'axes = get(gcf,''UserData'');',...
 		'cntlHndl = get(axes(1),''UserData'');',...
		'set(cntlHndl(1),''Value'',1),',...
 		'set(cntlHndl(10),''Value'',5);',...
 		'gbprop(''get info_1'')'];

	cntlPos = [xPos yPos-cntlHt cntlWid cntlHt];
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','pushbutton', ...
		'Units','normalized', ...
		'String',labelStr, ...
		'Position',cntlPos, ...
		'Callback',callbackStr);

	%====================================
	% Create the "Reset" control button
	cntlNumber = 6;
	yPos = cntlTop-(round(cntlNumber./2)-1)*(cntlHt+cntlSpacing);
	if rem(cntlNumber,2) == 0
		xPos = desRight - frmBorder - cntlWid;
	else
		xPos = desLeft + frmBorder;
	end
	labelStr = 'Reset';
	callbackStr=[...
		'delete(gcf);',...
		'gbprop(''initialize'')'];
    
	cntlPos = [xPos yPos-cntlHt cntlWid cntlHt];
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','pushbutton', ...
		'Units','normalized', ...
		'Position',cntlPos, ...
		'String',labelStr, ...
		'Callback',callbackStr);
	
	%====================================
	% Create the "Device entry" static text control
	cntlNumber = 7;
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','text', ...
		'Units','normalized', ...
		'Visible','off',...
		'BackgroundColor',[0.5 0.5 0.5],...
		'FontWeight','bold',...
		'ForegroundColor',[1 1 1],...	
		'HorizontalAlignment','Left');

	%====================================
	% Create "Popup" control
	cntlNumber = 8;

	popupStr = [...
		'positive lens|'...
		'negative lens|plane mirror|'...
		'concave mirror|convex mirror|'...
		'grin rod'];
	callbackStr = [...
 		'A = get(gcf,''UserData'');',...
 		'cntlHndl = get(A(1),''UserData'');',...
 		'set(cntlHndl(12),''Value'',8);',...
 		'gbprop(''get info_1'')'];
  
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','popup', ...
		'Units','normalized', ...
		'Visible','off',...
		'String',popupStr, ...
		'FontSize',[12],...
		'Position',cntlPos, ...
		'Callback',callbackStr);
	
	%====================================
	% Create the "First entry" static text control
	cntlNumber = 9;

	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','text', ...
		'Units','normalized', ...
		'Visible','off',...
		'HorizontalAlignment','Left',...
		'BackgroundColor',[1 1 1]);

	%====================================
	% Create the "First entry" editable text control
	cntlNumber = 10;

	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','edit', ...
		'Units','normalized', ...
		'HorizontalAlignment','Right',...
		'Visible','off',...
		'BackgroundColor',[1 1 1]);	

	%====================================
	% Create the "Second entry" static text control
	cntlNumber = 11;

	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','text', ...
		'Units','normalized', ...
		'Visible','off',...
		'HorizontalAlignment','Left',...
		'BackgroundColor',[1 1 1]);

	%====================================
	% Create the "Second entry" editable text control
	cntlNumber = 12;

	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','edit', ...
		'Units','normalized', ...
		'HorizontalAlignment','Right',...
		'Visible','off',...
		'BackgroundColor',[1 1 1]);	

	%====================================
	% Create the "Third entry" static text control
	cntlNumber = 13;

	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','text', ...
		'Units','normalized', ...
		'HorizontalAlignment','Left',...
		'Visible','off',...
		'BackgroundColor',[1 1 1]);
    
	%====================================
	% Create the "Third entry" editable text control
	cntlNumber = 14;
    
	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','edit', ...
		'Units','normalized', ...
		'HorizontalAlignment','Right',...
		'Visible','off',...
		'BackgroundColor',[1 1 1],'Max', 1);	

	%====================================
	% Create the "Data entry" static text control
	cntlNumber = 9;

	cntlHndl(cntlNumber) = uicontrol( ...
		'Style','text', ...
		'Units','normalized', ...
		'Visible','off');

	%==================================== 
	% The CLOSE button
	 uicontrol( ...
		'Style','push', ...
		'Units','normalized', ...
		'Position',[desRight-frmBorder-cntlWid...
			desBottom+frmBorder cntlWid cntlHt], ...
		'String','Close', ...
		'Callback','close(gcf)');

	% Save all of these handles for future use
	set(gca,'UserData',cntlHndl);
	% and make an initial presentation
	set(gcf,'Visible','on');	
	
		
%===================================
elseif strcmp(action,'get device')
	axes = get(gcf,'UserData');
 	cntlHndl = get(axes(1),'UserData');
	cntlPos = get(cntlHndl(5),'Position');
	Pos_1 = cntlPos - [0 cntlPos(4)+0.04 0 0];
	Pos_2 = Pos_1 + [cntlPos(3)+0.02 0 0 0];
	set(cntlHndl(7),...
		'String','Select a device',...
		'Position',Pos_1,...
		'Visible','on');
	set(cntlHndl(8),...
		'Position',Pos_2,...
		'Visible','on',...
		'CallBack','gbprop(''get info_1'')');
		
%===================================
elseif strcmp(action,'kill device')
	axes = get(gcf,'UserData');
 	cntlHndl = get(axes(1),'UserData');
 	region = get(0,'UserData');
	maxIndex = size(region,2);
	set(gco,'Selected','on');
	for index = 2:2:maxIndex-1
		if gco == region(index).pictHndl
			break
		end
	end
	set(cntlHndl(2),'Value',index);
	gbprop('get info_1');
	
%===================================
elseif strcmp(action,'get info_1')
	axes = get(gcf,'UserData');
	xLim = get(axes(2),'XLim');
 	cntlHndl = get(axes(1),'UserData');
	Pos_A = get(cntlHndl(5),'Position');
	Pos_B = get(cntlHndl(6),'Position');
	Pos_1 = [Pos_A(1) (Pos_A(1)-0.9*Pos_A(4))...
				1.55*Pos_A(3) 0.7*Pos_A(4)];
	Pos_2 = [Pos_B(1)+Pos_B(3)-0.6*Pos_B(3) Pos_1(2)...
				0.6*Pos_B(3) 0.5*Pos_B(4)];

	% Next action varies with button origin
	switch get(cntlHndl(10),'Value')
		case 1 % 'Initialize beam' button
			instrStr = 'Enter the position (cm) of the minimum beam width';
			numStr = sprintf('%2.1f',xLim(1));
			callStr = 'gbprop(''get info_2'')';
		
		case 2 % 'Add device' button 
 			xDim = xLim(2) - xLim(1);
			set(cntlHndl(7),'Visible','off');
			set(cntlHndl(8),'Visible','off');
			gbprop('mouse meter on');
			callStr = 'gbprop(''get info_2'')';
			switch get(cntlHndl(8),'Value')
				case 1
					instrStr = 'Where is the positive lens located?';
					numStr = sprintf('%2.1f',10*fix(xDim./20));
				case 2
					instrStr = 'Where is the negative lens located?';
					numStr = sprintf('%2.1f',10*fix(xDim./20));
				case 3
					instrStr = 'Where is the plane mirror located?';
					numStr = sprintf('%2.1f',10*fix(xDim./20));
					callStr ='gbprop(''make space'')';
				case 4
					instrStr = 'Where is the concave mirror located?';
					numStr = sprintf('%2.1f',10*fix(xDim./20));
				case 5
					numStr = sprintf('%2.1f',10*fix(xDim./20));
					instrStr = 'Where is the convex mirror located?';
				case 6
					numStr = sprintf('%2.1f',xLim(1));
					instrStr = 'Where does the "grin rod" region start?';
			end
	
		case 4 % 'Remove device' button 
			set(gcf,'WindowButtonDownFcn','default');
			instrStr = 'Remove the selected device?';
			numStr = 'yes';
			callStr ='gbprop(''make space'')';
	
		case 5 % 'Profile beam' button 
			gbprop('mouse meter on');
			instrStr = 'Where do you want to profile?';
			callStr = 'gbprop(''tas plot'')';
			numStr = sprintf('%2.1f',0);
	
	end
	set(cntlHndl(9),...
		'BackgroundColor',[0.5 0.5 0.5],...
		'ForegroundColor',[1 1 1],...				
		'String',instrStr,...
		'HorizontalAlignment','Left',...
		'Visible','on',...
		'Position',Pos_1);
	set(cntlHndl(10),...
		'HorizontalAlignment','Right',...
		'CallBack',callStr,...
		'Visible','on',...
		'Position',Pos_2,...
		'String',numStr)
	set(cntlHndl(1),'Value',2);


%===================================
elseif strcmp(action,'get info_2')
	axes = get(gcf,'UserData');
	set(gcf,'CurrentAxes',axes(2));
 	cntlHndl = get(axes(1),'UserData');
	cntlPos = get(cntlHndl(5),'Position');
	Pos_A = get(cntlHndl(9),'Position');
	Pos_B = get(cntlHndl(10),'Position');
	Pos_1 = [Pos_A(1) Pos_A(2)-Pos_A(4)-0.01...
				Pos_A(3) Pos_A(4)];
	Pos_2 = [Pos_B(1) Pos_1(2) Pos_B(3) Pos_B(4)];

	% Next action varies with button of origin
	switch get(cntlHndl(10),'Value')
		case 1 % 'Initialize beam' button
			gbprop('mouse meter off');
			callStr = 'gbprop(''get info_3'')' ;
			instrStr = 'Enter a value for the minimum beam width (cm)';
			numStr = sprintf('%2.1f',20);

		case 2 % 'Add device' button
			callStr = 'gbprop(''make space'')' ;
			gbprop('mouse meter off');
			xLim = get(axes(2),'XLim');
			xDim = xLim(2) - xLim(1);
			switch get(cntlHndl(8),'Value')
				case 1
					instrStr = 'What is the focal length of the lens?';
					numStr = sprintf('%2.1f',10*fix(xDim./100));
				case 2
					instrStr = 'What is the focal length of the lens?';
					numStr = sprintf('%2.1f',-10*fix(xDim./100));
				case 4
					instrStr = 'What is the focal length of the mirror?';
					numStr = sprintf('%2.1f',10*fix(xDim./100));
				case 5
					instrStr = 'What is the focal length of the mirror?';
					numStr = sprintf('%2.1f',-10*fix(xDim./100));
				case 6
					gbprop('mouse meter on');
					instrStr = 'Where does the "grin rod" region end?';
					numStr = sprintf('%2.1f',10*fix(xLim(2)./10));
					callStr = 'gbprop(''get info_3'')';
			end

	end
	set(cntlHndl(11),...
		'BackgroundColor',[0.5 0.5 0.5],...
		'ForegroundColor',[1 1 1],...				
		'String',instrStr,...
		'HorizontalAlignment','Left',...
		'Visible','on',...
		'Position',Pos_1);
	set(cntlHndl(12),...
		'HorizontalAlignment','Right',...
		'CallBack',callStr,...
		'Visible','on',...
		'Position',Pos_2,...
		'String',numStr )
	set(cntlHndl(1),'Value',3);

%===================================
elseif strcmp(action,'get info_3')
	gbprop('mouse meter off');
	axes = get(gcf,'UserData');
	set(gcf,'CurrentAxes',axes(2));
 	cntlHndl = get(axes(1),'UserData');
	callStr = 'gbprop(''make space'')';
	Pos_A = get(cntlHndl(11),'Position');
	Pos_B = get(cntlHndl(12),'Position');
	Pos_1 = [Pos_A(1) Pos_A(2)-Pos_A(4)-0.01...
				Pos_A(3) Pos_A(4)];
	Pos_2 = [Pos_B(1) Pos_1(2) Pos_B(3) Pos_B(4)];
	
	% Next action varies with button of origin
	switch get(cntlHndl(10),'Value')
		case 1 % 'Initialize beam' button
			instrStr = 'Enter a value for the wavelength (cm)';
			numStr = sprintf('%2.1f',1);

		case 2 % 'Add device' button
			if get(cntlHndl(8),'Value') == 6
					gbprop('mouse meter on');
					xLim = get(axes(2),'XLim');
					xDim = xLim(2) - xLim(1);
					instrStr = 'What is the spatial period of the grin rod';
					numStr = sprintf('%2.1f',20*round(xDim./100));
			end

	end
	set(cntlHndl(13),...
		'BackgroundColor',[0.5 0.5 0.5],...
		'ForegroundColor',[1 1 1],...				
		'String',instrStr,...
		'HorizontalAlignment','Left',...
		'Visible','on',...
		'Position',Pos_1);
	set(cntlHndl(14),...
		'HorizontalAlignment','Right',...
		'CallBack',callStr,...
		'Visible','on',...
		'Position',Pos_2,...
		'String',numStr )
	set(cntlHndl(1),'Value',4);
	
%===================================
elseif strcmp(action,'button motion')|strcmp(action,'button up')
	axes = get(gcf,'UserData');
	set(gcf,'CurrentAxes',axes(2));
	yLim = get(gca,'YLim');
 	cntlHndl = get(axes(1),'UserData');
	pt=get(gca,'CurrentPoint');
	if pt(1,2)<yLim(2) & pt(1,2)>yLim(1)
		set(gcf,'Pointer','crosshair');
		if 	get(cntlHndl(1),'Value') == 2
			set(cntlHndl(10),...
				'String',sprintf('%2.1f',pt(1,1)));
		elseif 	get(cntlHndl(1),'Value') == 3
			set(cntlHndl(12),...
				'String',sprintf('%2.1f',pt(1,1)));
		end
	else
		set(gcf,'Pointer','arrow');			
	end
	if strcmp(action,'button up')
		set(gcf,...
			'Pointer','arrow',...
			'WindowButtonMotionFcn','default');
	end	
	
%===================================
elseif strcmp(action,'make space')
	gbprop('mouse meter off');
	axes = get(gcf,'UserData');
	tasAxes = axes(1); lasAxes = axes(2);
	cntlHndl = get(tasAxes,'UserData');
	% Erase all of the data dialogs
	i = 0:7;
	set(cntlHndl(7 + i),'Visible','off');
	
	% Next action varies with button of origin
	switch get(cntlHndl(10),'Value')
		case 1 % 'Initialize beam' button
			set(cntlHndl(10),'UserData',...
				str2num(get(cntlHndl(10),'String')));
			% Calculate and save the Fresnel length
			W = str2num(get(cntlHndl(12),'String'));
			lamda = str2num(get(cntlHndl(14),'String'));
			set(cntlHndl(14),'UserData',lamda);
			L = (pi*W.^2)./lamda;
			set(cntlHndl(12),'UserData',L);
			set(lasAxes,...
				'XLim',[0 8*L],...
				'YLim',[-8*W 8*W]);		
			% Initialize propagation space
			region(1) = struct(...
				'name','free space',...
				'position',get(lasAxes,'XLim'),...
				'parameter',[],...
				'pictHndl',[]);
			set(0,'UserData',region);
			gbprop('las plot');

		case 2 % 'Add device' button
			xLim = get(lasAxes,'XLim');
			yLim = get(lasAxes,'YLim');
 			region = get(0,'UserData');
			maxIndex = size(region,2);
			devPos = str2num(get(cntlHndl(10),'String'));
			endPos = devPos;
			% We need to make sure space is free for the device
			for index = 1:maxIndex
				if strcmp(region(index).name,'grin rod')
					if devPos >= region(index).position(1) &...
							devPos <= region(index).position(2)
						error('The device overlaps a GRIN rod!');
						gbprop('get info_1');
					end
				end
			end
			switch get(cntlHndl(8),'Value')
				case 1
					rgnName = 'pos lens';
					rgnParam = str2num(get(cntlHndl(12),'String'));
				case 2
					rgnName = 'neg lens';
					rgnParam = str2num(get(cntlHndl(12),'String'));
				case 3
					rgnName = 'pln mirr';
					rgnParam = [];
				case 4
					rgnName = 'concv mirr';
					rgnParam = str2num(get(cntlHndl(12),'String'));
				case 5
					rgnName = 'convx mirr';
					rgnParam = str2num(get(cntlHndl(12),'String'));
				case 6
					rgnName = 'grin rod';
					endPos = str2num(get(cntlHndl(12),'String')); 
					rgnParam = str2num(get(cntlHndl(14),'String'));
					for index = 2:2:maxIndex-1
						if region(index).position(1) >= devPos &...
										region(index).position(2) <= endPos 
							error('The GRIN rod overlaps another device');
							gbprop('get info_1');
						end
					end
			end
			% Now we start sort out the order of things
			% First we get the starting positions in order
			switch maxIndex
				case 1
					region(3) = region(1);
					region(2).position = [devPos endPos];
					region(1).position(2) = devPos;
					region(3).position(1) = endPos;
					nuIndex = 2;
				
				case 3
					region(5) = region(3);
					if devPos > region(2).position(1)
						region(4).position = [devPos endPos];
						region(3).position(2) = devPos;
						region(5).position(1) = endPos;
						nuIndex = 4;
					else
						region(4) = region(2);
						region(2).position = [devPos endPos];
						region(1).position(2) = devPos;
						region(3).position(1) = endPos;
						region(3).position(2) = region(4).position(1);
						nuIndex = 2;
					end
			
				otherwise
					for nuIndex = 2:2:maxIndex-1
						if devPos < region(nuIndex).position(1)
							break
						end
					end
					if nuIndex == maxIndex-1
						nuIndex = maxIndex + 1;
						region(nuIndex+1) = region(nuIndex-1);
						region(nuIndex).position = [devPos endPos];
						region(nuIndex-1).position(2) = devPos;
						region(nuIndex+1).position(1) = endPos;
					else
						for i = nuIndex:maxIndex 
							region(maxIndex+nuIndex-i+2)...
								= region(maxIndex+nuIndex-i);
						end
						region(nuIndex).position = [devPos endPos];
						region(nuIndex-1).position(2) = devPos;
						region(nuIndex+1).position(1) = endPos;
						region(nuIndex+1).position(2) =...
								region(nuIndex+2).position(1);
					end
			
				end
				region(nuIndex).name = rgnName;
				region(nuIndex).parameter = rgnParam;
				set(cntlHndl(2),'Value',nuIndex);
				set(0,'UserData',region);
				gbprop('device plot');
				
			case 4 % 'Remove device' button 
				devNum = get(cntlHndl(2),'Value');
 				region = get(0,'UserData');
				maxIndex = size(region,2);
				if strcmp(get(cntlHndl(10),'String'),'yes')
					pictHndl = region(devNum).pictHndl;
					for index = devNum+2:maxIndex
						region(index-2) = region(index);
					end
					region(devNum-1).position(2) =...
							region(devNum).position(1);
					region = region(1:maxIndex-2);
					delete(pictHndl);
				else
					set(region(devNum).pictHndl,'Selected','off');
				end
				set(0,'UserData',region);
			
		end

%===================================
elseif strcmp(action,'las plot')
	axes = get(gcf,'UserData');
	tasAxes = axes(1); lasAxes = axes(2);
	cntlHndl = get(tasAxes,'UserData');
	L = get(cntlHndl(12),'UserData');
	z0 = get(cntlHndl(10),'UserData');
	maxPts = 201;
	xLim = get(lasAxes,'XLim');
	yLim = get(lasAxes,'YLim');
	xDim = xLim(2) - xLim(1);
	xDiff = xDim/(maxPts - 1);
	ticNum = xDim./L - 1;

	% Action varies with button origin
	switch get(cntlHndl(10),'Value')
		case 1 % 'Initialize beam' button
			X=linspace(0,xDim,ticNum+2);
			for n =4:3*(ticNum+2)
				x(n)=X(round((n+1)./3));
				if rem(n,3)==2
					y(n)=yLim(2)/20;
				else
					y(n)=0;
				end
			end
			plot(x,y,'w')
			index = 1:maxPts;
			z = xDiff*(index - 1);
			q = (z - z0) + j*L;

		case 3 % 'Launch beam' button
			delete(get(cntlHndl(3),'UserData'));
			region = get(0,'UserData');
			maxRgn = size(region,2);
			m =1; n = 1;
			bakProp = 1;
			q(1) = -z0 + j*L;
			z(1) = 0;
			while n <= maxRgn,
				if bakProp < 0
					while z(m) > region(n).position(1),
						z(m+1) = z(m) - xDiff;
						q(m+1) = q(m) + xDiff;
						m = m + 1;
					end
					n = n - 1;
				else
					while z(m) < region(n).position(2),
						z(m+1) = z(m) + xDiff;
						q(m+1) = q(m) + xDiff;
						m = m + 1;
					end
					n = n + 1;
				end			
				if n >= maxRgn | n <= 0
					break
				end
				switch region(n).name
					case {'pos lens', 'neg lens'}
						z(m+1) = z(m);
						q(m+1) = q(m)./(1-q(m)./region(n).parameter);
						m = m + 1;
						n = n + 1;
					case 'pln mirr'
						z(m+1) = z(m);
						q(m+1) = q(m);
						m = m + 1;
						n = n - 1;
						bakProp = -bakProp;
					case {'concv mirr', 'convx mirr'}
						z(m+1) = z(m);
						q(m+1) = q(m)./(1-q(m)./region(n).parameter);
						m = m + 1;
						n = n - 1;
						bakProp = -bakProp;
					case 'grin rod'
						fac1 = 2*pi./region(n).parameter;
						fac2 = tan(fac1*xDiff);
						while z(m) < region(n).position(2),
							z(m+1) = z(m) + xDiff;
							q(m+1) = (q(m)+fac2./fac1)./(-fac1*fac2*q(m)+1);
							m = m + 1;
						end
						n = n + 1;
				end
			end
			maxPts = size(z,2);
	end

	set(gca,'UserData',[z; q]); % Save data array for transverse plots
	lamda = get(cntlHndl(14),'UserData');
	qInv = 1./q;
	W = sqrt(-lamda./(pi*imag(qInv)));
	F = (pi*L./lamda)./8; % Aspect ratio factor
	plotHndl(1) = plot(z,W,'r-','LineWidth',[2]);
	plotHndl(2) = plot(z,-W,'r-','LineWidth',[2]);
	tic = 1; index = 1;
	while tic <= ticNum+1 & get(cntlHndl(10),'Value') == 1
		while 1,
			if z(index) > rem(z0,L) + (tic-1)*L
				break
			end
			index = index + 1;
		end
		if real(qInv(index-1)) ~= 0
			R = 1./real(qInv(index-1));
			m = 1:10;
			y = (m-1)*W(index)/9;
			if R > 0
				x = z(index-1)-F*(R-sqrt(R.^2-y.^2));
			else
				x = z(index-1)-F*(R+sqrt(R.^2-y.^2));
			end
			next = size(plotHndl,2);
			plotHndl(next+1) = plot(x,y,'g');
			plotHndl(next+2) = plot(x,-y,'g');
		end
		tic = tic + 1;
	end
	set(cntlHndl(3),'UserData',plotHndl); % Save for erase

%===================================
elseif strcmp(action,'device plot')
	axes = get(gcf,'UserData');
	tasAxes = axes(1); lasAxes = axes(2);
	cntlHndl = get(tasAxes,'UserData');
	xLim = get(lasAxes,'XLim');
	yLim = get(lasAxes,'YLim');
	xDim = xLim(2) - xLim(1);
	region = get(0,'UserData');
	set(gcf,'CurrentAxes',lasAxes);
	devPos = str2num(get(cntlHndl(10),'String'));
	devParam = str2num(get(cntlHndl(14),'String'));
	devNum = get(cntlHndl(2),'Value');
	D=xDim./50;
	R=xDim./6;
	H=1.9*yLim(1);
	switch get(cntlHndl(8),'Value')
		case 1
			x1=devPos+linspace(-D,0,20);
			y1=H*real(sqrt(1-((x1-devPos+D)./R-1).^2));
			x2=devPos+linspace(0,D,20);
			y2=H*real(sqrt(1-((x2-devPos-D)./R+1).^2));
			x3=devPos+linspace(D,0,20);
			y3=-H*real(sqrt(1-((x3-devPos-D)./R+1).^2));
			x4=devPos+linspace(0,-D,20);
			y4=-H*real(sqrt(1-((x4-devPos+D)./R-1).^2));;
			shape=[[y1; x1] [y2; x2] [y3;x3]  [y4;x4]];
		case 2
			x1=devPos+linspace(-D,0,20);
			y1=H*sqrt(1-((-x1+devPos)./R-1).^2);
			x2=devPos+linspace(0,-D,20);
			y2=-H*sqrt(1-((-x2+devPos)./R-1).^2);;
			x3=devPos+linspace(D,0,20);
			y3=-H*sqrt(1-((-x3+devPos)./R+1).^2);
			x4=devPos+linspace(0,D,20);
			y4=H*sqrt(1-((-x4+devPos)./R+1).^2);
			x0=devPos+D;
			y0=H*sqrt(1-(D./R-1).^2);
			shape=[[y0; x0] [y1; x1] [y2; x2] [y3;x3] [y4;x4]];
		case 3
			x0=devPos-D./6;
			y0=H./2;
			x1=devPos+D./6;
			shape=[[y0; x0] [y0; x1] [-y0; x1] [-y0;x0] [y0;x0]];
		case 4
			x0=devPos-D; 
			y0=H*sqrt(1-(D./R-1).^2);
			x1=devPos+linspace(-D,0,20);
			y1=H*sqrt(1-((-x1+devPos)./R-1).^2);
			x2=devPos+linspace(0,-D,20);
			y2=-H*sqrt(1-((-x2+devPos)./R-1).^2);;
			shape=[[y1; x1] [y2; x2]...
						[-y1; x1+D./3] [-y2; x2+D./3]];
		case 5
			x0=devPos+D;
			y0=H*sqrt(1-(D./R-1).^2);
			x3=devPos+linspace(D,0,20);
			y3=-H*sqrt(1-((-x3+devPos)./R+1).^2);
			x4=devPos+linspace(0,D,20);
			y4=H*sqrt(1-((-x4+devPos)./R+1).^2);
			shape=[[y3; x3] [y4; x4]...
						[-y3; x3+D./3] [-y4;x4+D./3]];
		case 6
			endPos = str2num(get(cntlHndl(12),'String'));
			x0=devPos;
			y0=H./2;
			x1=endPos;
			shape=[[y0; x0] [y0; x1] [-y0; x1] [-y0;x0] [y0;x0]];
	end
	region(devNum).pictHndl = patch(shape(2,:),shape(1,:),'c','EdgeColor','c');
	set(0,'UserData',region);

%===================================
elseif strcmp(action,'tas plot')
	axes = get(gcf,'UserData');
	tasAxes = axes(1); lasAxes = axes(2);
	cntlHndl = get(tasAxes,'UserData');
	lasData = get(lasAxes,'UserData');
	for i = 0:7
		set(cntlHndl(7 + i),'Visible','off');
	end
	set(gcf,'CurrentAxes',tasAxes);
	set(gca,'View',[30 30]);
	z = lasData(1,:); q = lasData(2,:);
	maxIndex = size(z,2);
	for i = 1:maxIndex
		if z(i) > str2num(get(cntlHndl(10),'String'))
			break;
		end
	end
	qInv = 1./q(i);
	W=sqrt(-1./imag(qInv));
	x = linspace(-2*W,2*W,30);
	y = x;
	[X,Y] = meshgrid(x,y);
	Z=exp(imag(qInv)*(X.^2 + Y.^2));
	surf(X,Y,Z)
	

%===================================
elseif strcmp(action,'mouse meter on')
	set(gcf,...
		'Pointer','crosshair',...
		'WindowButtonUpFcn','gbprop(''button up'')',...
		'WindowButtonMotionFcn','gbprop(''button motion'')');

%===================================	
elseif strcmp(action,'mouse meter off')
	set(gcf,...
		'Pointer','arrow',...
		'WindowButtonUpFcn','default',...
		'WindowButtonMotionFcn','default');

%===================================	
end		% if strcmp(action, ...