Updating a string inside a callback - string

Question

The following code is a graphic rendering of the Earth globe spinning eastward. I have two push buttons, Spin and Stop. Both share the same callback function, hAnimaCallback. In particular, this latter does not work. I pretend to use the strings (names) of the push buttons to create a switch that stops the movement. However, I can not get to change the string name inside the while loop and I do not understand why my method is wrong.
function example
fh = figure('Menu','none','Toolbar','none','Units','characters');
T = 0:pi/100:2*pi;
Y = zeros(numel(T),3);
Y(:,1) = 7000*cos(T);
Y(:,2) = 7000*sin(T);
hPanAni = uipanel('parent',fh,'Units','characters','Position',...
[22.6 10.4 53 23],'title','Controls','FontSize',11,...
'FontAngle','italic','FontWeight','bold');
hIniAni = uicontrol(hPanAni,'Style','pushbutton','Units','normalized',...
'Position',[0.14 0.64 0.5 0.12],'String','Spin',...
'FontSize',10,'Callback',#hAnimaCallback);
hFinAni = uicontrol(hPanAni,'Style','pushbutton','Units','normalized',...
'Position',[0.14 0.26 0.5 0.12],'String','Stop',...
'FontSize',10,'Callback',#hAnimaCallback);
hPantSim = uipanel('Parent',fh,'Units','characters',...
'Position',[107.87 8 157.447 42],'BorderType','none','title',...
'Screen','FontSize',11,'FontAngle','italic',...
'FontWeight','bold');
hPantSimInt = uipanel('Parent',hPantSim,'Units','normalized','Position',...
[0 0 1 1],'BorderType','line','BackgroundColor','black');
ah4 = axes('Parent',hPantSimInt,'Units','normalized','Position',...
[0 0 1 1],'Color','none','Visible','off','DataAspectRatio',...
[1 1 1],'NextPlot','add');
rotate3d(ah4);
hgrot = hgtransform('Parent',ah4);
Resf = 6378;
maptext = imread('tierra.jpg');
[X, map] = rgb2ind(maptext,128);
[x,y,z] = sphere(50);
x = Resf*x;
y = Resf*y;
z = Resf*z;
props.FaceColor= 'texture';
props.EdgeColor = 'none';
props.Parent = hgrot;
props.Cdata = flipud(X); % it is necesary to do this for getting the
% appropiate image on the sphere
hsurf = surface(x,y,z,props);
colormap(map);
axis equal;
view([71 14]);
set(gcf,'Renderer','opengl')
drawnow;
line('parent',ah4,'XData',Y(:,1),'YData',Y(:,2),'ZData',...
Y(:,3),'Color','red','LineWidth',2);
line('parent',ah4,'XData',Y(end,1),'YData',Y(end,2),...
'ZData',Y(end,3),'Marker','o','MarkerSize',6,'MarkerFaceColor','b');
axis square equal vis3d;
view(3);
handles.XLim = get(ah4,'XLim');
handles.YLim = get(ah4,'YLim');
handles.ZLim = get(ah4,'ZLim');
xmin = handles.XLim(1);
ymin = handles.YLim(1);
zmin = handles.ZLim(1);
xmax = handles.XLim(2);
ymax = handles.YLim(2);
zmax = handles.ZLim(2);
set(ah4, 'XLim', [xmin xmax],'YLim', [ymin ymax],'Zlim',[zmin zmax]);
az = 0;
function hAnimaCallback(hObject,evt)
while (ishandle(fh))
state = get(hObject,'String'), % state should change between the states of
% Spin and Stop but this does not occur
if (strcmp(state,'Stop'))
break;
else
az = az + 0.01745329252;
set(hgrot,'Matrix',makehgtform('zrotate',az));
drawnow;
end
end
end
end

Answer 1

It seems like you are running into some kind of race condition because of the repeated drawnow calls in the while loop. The state changes to Stop, when you press the Stop button, but it is to quick to notice. Basically, the while loop is running as fast as MATLAB can run. Instead of drawnow using a pause(0.1) command seems to work (with a little bit code logic changes):
az = 0;
spin = false;
function hAnimaCallback(hObject,~)
state = get(hObject,'String')
if strcmp(state, 'Spin')
spin = true;
else
spin = false;
end
while (spin)
az = az + 0.01745329252;
set(hgrot,'Matrix',makehgtform('zrotate',az));
pause(0.1);
end
end