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How to implement a 'speed limit' for GUI button press?

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John on 19 Apr 2011
Hi, I have a GUI built to flip through slices of large 3D image matrices and adjust visualization parameters. When changing slices with a slider, if the slider is clicked too fast in succession the GUI lags a lot because it is trying to render each intermediate image. I want to add a button press 'speed limit' such that: if slider clicks > 1 && time < threshold, skip displaying the intermediate images and just generate display for the final slider setting, else, refresh the image for each slider click, end
I don't know what functions I could use to implement that, as it's not really a timeout. Schemes I can think of using tic, toc or uiwait would require a second click which may not be coming. Any ideas would be appreciated! Thanks!
  1 Comment
John on 19 Apr 2011
Thanks to all for the suggestions. While Matt's answer works, it forces the user to wait between clicks whereas Paulo's answer allows the user to click at will and provides them with a smoother experience regardless. Also, I found that adding 'drawnow' at the end of the image generation code made that function a lot more responsive, which alone fixed the problem for small to moderately sized data sets.

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Accepted Answer

Paulo Silva
Paulo Silva on 19 Apr 2011
Use a timer (execution mode 'singleShot') in the slider callback:
  1. Check if the timer is running, if not start it and run the slider code
  2. If the timer is already running ignore all the rest of the slider code
  1 Comment
Sean de Wolski
Sean de Wolski on 19 Apr 2011
Good answer.
You could also have the timer disable the slider until it's done.

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More Answers (2)

Matt Fig
Matt Fig on 19 Apr 2011
Just set the 'enable' property to 'inactive' as the first command of the callback, then as the last command, set the 'enable' property to 'on'.

Malcolm Lidierth
Malcolm Lidierth on 19 Apr 2011
Change the callback mode to to 'cancel' instead of 'queue'. Alternatively, test for multiple calls in the callback using isMultipleCall from the FEX. if isMultipleCall();return;end
Yair Altman
Yair Altman on 21 Jul 2011
Matt - if you add even a short pause(0.1) in your callback string then the busyaction=cancel does indeed run only once, not 3 times. My hunch is that what happens under the hood is that the callback is actually delegated to a separate thread (maybe EDT delegating to the MT?). This delegation happens so quickly that if you double-click the separate clicks do not in fact overlap, and both callbacks will then get executed one after another. However, when you add a pause, it forces the interpreter to use the original thread (instead of delegating), and in this case the clicks *do* overlap and so the second click is discarded.

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