How to put a timeout to ginput.

I want to show user a figure, and ask them to click somewhere within a stipulated time limit, like 2 seconds.

I am using ginput as follows, but it seems to be pausing the execution before a button is pressed. I went to check in the ginput function and indeed it was using waitforbuttonpress. I tried some hands in getting a workaround but wasn't much succesfull to interrup ginput (specifically it's wfbp function).

I am attaching a sample code what i need.

I am okay in getting to know some work-arounds, even if they don't use ginput, but i'd still love to know what exactly could ba a solution if I were to use ginput.

Thanks in advanced

x = linspace(0,4*pi,2000);
y=sin(x);
plot(x,y);

timeout=2;
tic;
[xt,yt]=ginput(1);
if toc>2
    xt=NaN;
    yt=NaN;
end

Answer 1

[Sudarsanan A K]

Hi Akshat,

I understand that your goal is to show a figure and ask the user to click somewhere within a stipulated time limit (e.g., 2 seconds). The following approach would enable you achieve this:

1. Plot the Figure: Plot the figure you wish to show the customer.
2. Initialize Coordinates: Initialize "xt" and "yt" to "NaN".
3. Create Click Flag: Create a flag "clicked" to check if the user has clicked.
4. Create Timer: Create a timer object "t" with a "StartDelay" of "timeout" seconds. Set the "TimerFcn" to "uiresume(gcbf)", which resumes the figure's execution when the timer elapses.
5. Start Timer: Start the timer with "start(t)".
6. Set Mouse Click Callback: Set the "WindowButtonDownFcn" to "mouseClickFcn", which sets the "clicked" flag to "true" and resumes the figure's execution when the user clicks.
7. Wait for User Input or Timeout: Use the "uiwait(gcf, timeout)" function to wait for the figure to be resumed by either the timer or the mouse click.
8. Clean Up Timer: Stop and delete the timer object with "stop(t)" and "delete(t)".
9. Check Click Flag: Check if the "clicked" flag is "true" to determine if the user clicked within the timeout period.
10. Display Coordinates: Print the clicked coordinates to the console.

Here is an example:

timed_example();

function timed_example()
    x = linspace(0, 4*pi, 2000);
    y = sin(x);
    plot(x, y);

    timeout = 2;
    [xt, yt] = deal(NaN);  % Initialize the coordinates

    % Create a flag to check if the user has clicked
    clicked = false;

    % Create a timer object to interrupt the execution after the timeout
    t = timer('StartDelay', timeout, 'TimerFcn', @(~,~) uiresume(gcbf));
    start(t);

    % Set the WindowButtonDownFcn to capture the click and resume the figure
    set(gcf, 'WindowButtonDownFcn', @mouseClickFcn);

    % Wait for the figure to be resumed by either the timer or the mouse click
    uiwait(gcf, timeout);

    % Clean up the timer object
    stop(t);
    delete(t);

    % Display the clicked coordinates if clicked within the timeout
    if clicked
        fprintf('Clicked coordinates: (%f, %f)\n', xt, yt);
    else
        fprintf('No click detected within the timeout period.\n');
    end

    function mouseClickFcn(~, ~)
        % Capture the coordinates of the click
        coords = get(gca, 'CurrentPoint');
        xt = coords(1, 1);
        yt = coords(1, 2);
        clicked = true;
        uiresume(gcbf);
    end
end

The following resources are useful for further explorations:

• https://www.mathworks.com/help/matlab/creating_plots/capturing-mouse-clicks.html
• https://www.mathworks.com/help/matlab/creating_plots/create-callbacks-for-graphics-objects.html
• "uiwait": https://www.mathworks.com/help/matlab/ref/uiwait.html
• "uiresume": https://www.mathworks.com/help/matlab/ref/uiresume.html

I hope this helps!

[Akshat]

It worked, though i was looking for a one line solution like ginput only, this will do for now I guess. thanks.