Block GUI in Callback

Dear all,

how can I block interaction with a GUI, while a callback is executed. I'd like to create a GUI where by clicking a button a dialog to select a file opens and afterwards something is done to the file that is pretty time-consuming. Suprisingly, the callback is somehow executed in parallel, so it doesn't automatically block execution and this leads to undesired behaviour, because you could open the file-open-dialog again and I'd prefer to make this less annoying.

For illustration I created a small class:

classdef testGUI < handle
    properties(Access = private)
        hMainFigure
    end
    methods(Access = public)
        function this = testGUI()
            this.hMainFigure = figure('Visible', 'off');
            uicontrol('Style', 'pushbutton', 'String', 'Test', 'Callback', @this.testCallback, 'Parent', this.hMainFigure, 'Units', 'normalized', 'Position', [0,0,1,1]);
            this.hMainFigure.Visible = 'on';
        end
    end
    methods(Access = private)
        function testCallback(~, ~, ~)
            % -- deactivate main figure
            pause(2);
            % -- activate main figure
            fprintf('test\n');
        end
    end
end

If you click the button, the callback is executed and you can immediately click the button again - I would like to block the entire GUI until the callback (here the pause) is finished.

Thanks in advance,

Torsten

Answer 1

[Geoff Hayes]

Torsten - you could disable the button so that it can't be pressed again

        function testCallback(~, hButtonObj, ~)
            % -- deactivate main figure
            set(hButtonObj, 'Enable', 'off');   % <----- disable button
            pause(2);
            % -- activate main figure
            fprintf('test\n');
            set(hButtonObj, 'Enable', 'on');    % <----- enable button
        end

Of course, if you have several buttons or fields, you would need to block all of them too. Or consider using a Indeterminate Progress Bar....I think it is modal so while it is present, the user shouldn't be able to interact with your GUI.

[Torsten Knüppel]

Hi Geoff,

thanks for the quick reply. Unfortunately, I have some more controls in my actual GUI and I would like to avoid writing a separate function taking care of (de)activating each. Your suggestion with the indeterminate progress bar would have been very nice - unfortunately it doesn't seem to work with normal figures and this entire uifigure stuff is not working properly in my release (R2018a).

Thanks a lot and best regards!

[Geoff Hayes]

hmmm..what about a regular dialog

function testCallback(gui, ~, ~)
    % -- deactivate main figure
    hDialog = dialog('Units', 'normalized','Position',[0.45 0.45 0.2 0.1],...
        'Name','Calculation in progress...', 'CloseRequestFcn', '');
    get(hDialog)
    pause(5);
    % -- activate main figure
    set(hDialog, 'CloseRequestFcn','closereq');
    close(hDialog);
    fprintf('test\n');
end

Note that the CloseRequestFcn property is set to an empty string to prevent the user from closing the dialog via the x button in the top-left or top-right of the dialog. We then need to reset this before calling close(hDialog).

[Torsten Knüppel]

Thanks again for the suggestion - I played around with it and it does work with the 'pause', but unfortunately not with normal calculations. If I run the following script, the dialog window doesn't show up (proably because it is immediately closed) and the GUI is not blocked.

classdef testGUI < handle
    properties(Access = private)
        hMainFigure
    end
    methods(Access = public)
        function this = testGUI()
            this.hMainFigure = figure('Visible', 'off');
            uicontrol('Style', 'pushbutton', 'String', 'Test', 'Callback', @this.testCallback, 'Parent', this.hMainFigure, 'Units', 'normalized', 'Position', [0,0,1,1]);
            this.hMainFigure.Visible = 'on';
        end
    end
    methods(Access = private)
        function testCallback(this, ~, ~)
            hDialog = dialog('Units', 'normalized','Position',[0.45 0.45 0.2 0.1], 'Name','Calculation in progress...', 'CloseRequestFcn', '');
            get(hDialog);
            
            this.doSomething();
            
            set(hDialog, 'CloseRequestFcn','closereq');
            close(hDialog);

            fprintf('test\n');
        end
        function doSomething(~)
            n = 0;
            for i = 1:1e3
                n = n + sum(rand(1e5, 1));
            end
            fprintf('%d\n', n);
        end
    end
end

[Geoff Hayes]

I suppose if the doSomething function returned a value that your testCallback was "waiting" for then the dialog would stay visible.

[Torsten Knüppel]

Unfortunately, this didn't work as expected. If I return n in the above example, nothing changes.

[Torsten Knüppel]

I went with your first suggestions and introduced a small function to enable and disable all controls in a figure:

function disableGraphicsObjects(hGraphics, flag)
    if(isprop(hGraphics, 'Enable'))
        hGraphics.Enable = flag;
    end
    
    if(isprop(hGraphics, 'Children'))
        for child = hGraphics.Children(:)'
            disableGraphicsObjects(child, flag);
        end
    end
end

It does the trick for controls that are direct children of a figure - but I still need to test, if it also propagates to objects contained in a panel.

Answer 2

[Rik]

This is the way I solved it in my PhotoAnnotation tool:

%appdata is the guidata struct (which I now think was a poor choice as a name)
ButtonCallbackBuzy=appdata.ButtonCallbackBuzy;
if ButtonCallbackBuzy
    return%ignore key presses if a callback is already in progress
else
    appdata.ButtonCallbackBuzy=true;
    guidata(appdata.fig,appdata);
end

You do need to carefully keep track of when you load and save the guidata struct.

It might be a better idea to write a getter and setter function to do it:

%in your functions that need to check if the busy flag is set:
if getIfBusyFlag(gcbf)
    return%ignore
else
    setIfBusyFlag(gcbf,true)
end
%long running code
setIfBusyFlag(gcbf,false)

%getter and setter
function isBusy=getIfBusyFlag(hfig)
isBusy=false;
if ~isappdata(hfig,'isBusy')
    setappdata(hfig,'isBusy',isBusy);
else
    isBusy=getappdata(hfig,'isBusy');
end
end
function setIfBusyFlag(hfig,isBusy)
setappdata(hfig,'isBusy',isBusy);
end

[Rik]

I you're using a class-based GUI this is of course trivial with a property.

[Torsten Knüppel]

Very interesting suggestion, thanks a lot. But I went with something along the lines of Geoff's first answer - because your idea was not really applicable in my case (at least not so easily). I have a button that loads a file and a couple of controls to change parameters. On the one hand, if these parameters are changed the data from the file is processed and on the other hand, the ranges of the controls are affected by the data in the file. So I really would like to disable the entire GUI until the file is loaded, so that all values can be properly set and I don't run into an inconsistent state. Following your idea, I could introduce a flag "fileIsLoading" that I check whenever something is changed, but that would probably mean quite some overhead, that I'd like to avoid.

[Rik]

That is of course your call, although I doubt this will cause a lot of overhead. You could time how long these function take, but it is up to you to decide if that performance penalty is worth it.