Get a GUI to update while a loop is running

I have a GUI with a "Run" button that runs a filter on a continuous stream of images. The "Run" button callback function is "interruptible" = "on" and the "BusyAction" is "queue". I then adjust a slider which adjusts the filter that the "Run" loop is using and updates the GuiData handles variable. The problem is that the filter update is not recognised, until I stop the "Run" loop, and repress the "Run" button. Does anyone know how to get a running loop to use the latest version of a variable in the GuiData handles structure?

For example, the Run Function

function run_pushbutton_Callback(hObject, eventdata, handles)

if get(handles.run_pushbutton,'UserData')==1, return; end
set(handles.run_pushbutton,'UserData',1);
while (get(handles.run_pushbutton,'UserData') ~= 0)
    % Increment the image number
    handles.curImgNum = handles.curImgNum + 1;
    guidata(hObject,handles);    % Save the data      
    tempFiltWgt = handles.temporalFiltWeight/100
    % Run the filter weight on the images...
    % ...
end

Stop Function

function stop_pushbutton_Callback(hObject, eventdata, handles)

disp('STOP pressed.')
set(handles.run_pushbutton,'UserData',0);

Slider Function

function temporal_slider_Callback(hObject, eventdata, handles)

%obtains the slider value from the slider component
handles.temporalFiltWeight = get(handles.temporal_slider,'Value');

% Update handles structure
guidata(hObject, handles);

I have taken out all of the non-essentials to make the code clear. I am constantly updating the GuiData handles structure to try to keep everything up to date, but it won't seem to be updated in a function that has been interrupted. Is there any solution?

Answer 1

[Teja Muppirala]

Instead of having this

%obtains the slider value from the slider component
handles.temporalFiltWeight = get(handles.temporal_slider,'Value');

in the slider callback, you could put this code as the first line inside the while loop in the run_pushbutton callback. Would that work?

[MechtEngineer]

Absolutely spot on Teja! It works brilliantly. Before I had to actually stop the loop and then change the value and then restart, now I can change the setting live and view the results! Thanks a lot.

Answer 2

[Titus Edelhofer]

Try to put a drawnow into the loop to allow the event queue to be processed.

Titus

[Jan]

Exactly.

[MechtEngineer]

Could you advise where I put the drawnow? I have tried putting the drawnow at various spots within the "run" loop and it hasn't made any difference.

I put in

drawnow;

and

drawnow; pause(0.1);

Neither worked, and I put them in multiple places within the "run" and "slider" loops. I was a bit surprised when it didn't work.

If you don't know why, don't worry about it, as Teja Muppirala's advice down below works a treat! But I would like to see the performance with drawnow too.

[Lance Darragh]

I had a similar issue as in this post. Adding the drawnow command as the second line (the first being the one suggested as the original solution) fixed the problem, both were needed. Neither one by itself fixed the problem. Thank you all for your suggestions. By the way, it doesn't hurt to keep the statement in the slider callback function as well, in case it is needed outside of this while loop.

Answer 3

[Robert Cumming]

As well as the drawnow command you could try putting a pause (0.1) in - this can help refresh graphics in the queue.

[Jan]

Some Java updates are performed after PAUSE(0.02) only, e.g. to get the contents of UICONTROLs by GETFRAME. But in the OP's problem 0.1 sec would mean a remarkable slowdown, so I'd prefer DRAWNOW.

[Robert Cumming]

To be honest I didn't examine the OP code, only the general problem - and my answer was to complement the drawnow if it didn;t do it (for whatever reason), and do agree that it could cause a slow down if called a lot!