Disable windowkeypressfcn when specific child is on focus (app designer)

Is there a way to disable windowkeypressfcn when a specific child is on focus

For example,

I have a slider and an edit box and created a windowkeypressfcn to allow me to change the slider value by pressing left and rightarrow button.

I want the slider stay in place while user is adding input into the editbox.

Any ideas?

[Walter Roberson]

No, there is not. However, you can have the callback check if the slider is in focus (with gco) and return if it is.

[JIAYING WU]

Not sure why but gco only returns "0x0 empty GraphicsPlaceholder array" no matter which object I clicked inside the UIFigure.

[Ned]

I suggest you make an addition to the winkdowkeypressfcn where it stops controlling the slide object after a certain key combo has been entered. You can have it reactivate on the same, or another key combo.

Gotta love some of the gymnastics required to use App designer.

Answer 1

[Walter Roberson]

foo = uicontrol('style','slider', 'min', 0, 'max', 1);
foo.Callback = @(hObject, event) fprintf('slider %g gco %g\n', double(hObject), double(gco))
fig = gcf;
fig.WindowKeyPressFcn = @(hObject, event) fprintf('keypressfcn %g gco %g\n', double(hObject), double(gbo));

WIth the above, the behavior is:

• type outside of the slider: keypressfcn fires and hObject and gco both show up as 1 (the figure number)
• type inside the slider when the last item clicked was the arrows of the slider: keypressfcn fires and hObject shows the figure 1 and gco shows the ID of the slider
• type inside the slider when the last item clicked was inside the slider: keypressfcn fires and hObject shows the figure 1 and gco shows the ID of the slider (this is the same behavior as above)
• click on the arrows on the slider when the last item clicked or typed on was the figure: slider callback fires and hObject shows the ID of the slider and gco shows 1 (the figure number)
• click on the arrows on the slider when the last item clicked (other than the arrows) or typed on, was inside the slider: slider callback fires and hObject shows the ID of the slider and gco shows the id of the slider
• click on the arrows of the slider when you have not yet typed on the slider after the figure was in focus, and your clicks on the slider (if any() have been restricted to the arrows of the slider rather than inside the slider: slider callback fires and hObject shows the ID of the slider and gco shows the id of the figure.

To phrase this a different way: when you type, the underlying object is brought into focus and becomes gco but hObject is the figure against which the keypressfcn is registered. When you click on the arrows of the slider when the focus is the figure, then slider callback fires, focus of the figure is not given up and hObject is the slider but gco is the figure. When you click on the arrows of the slider when the focus is on the slider because you either clicked or typed in the slider, then slider callback fires, hObject is the slider and so is gco. When you click insider the slider, then slider callback fires, hObject is the slider and so is gco.

In every case where you type over the arrows or any other part of the slider, then although hObject of the keypressfcn is the figure, gco is the slider.

Therefore you can detect the focus being the slider by checking that gco is the slider; more generally that hObject is not the same as gco (but that would include anything else that the user accidentally typed on while hovering over.)

[JIAYING WU]

Thank you for your answer. It is very clear and helpful. And I'm sure it definitely works with GUIDE. My problem is I don't know how to implement it in App Designer 2019, seems gco is not supported anymore.

[Walter Roberson]

I just tested with App Designer. gco only showed me 1 (the figure number), but was never empty. gcbo showed me 2.something for key presses, and 3.something for slider clicks. This was not sufficient to determine if you were typing above a slider.

I do not know enough about app designer to make further suggestions at this time.

[Ned]

For me, gco is returning a 0x0 empty GraphicsPlaceholder array, and gcbo returns the figure for both outputs.

[Walter Roberson]

Example enclosed. Typing will display information through callback, and moving the slider will display information through callback.

[Ned]

gco is still returning nothing for me. this is what my output looks like

Did some testing and gcbo is actually working properly and giving you the source of the callback that's calling it. So it's always going to return the UIFigure as it's value, because the UIFigure is the ONLY element with a KeyPresssFcn.

Also learnt that the KeyPressFcn only works when the figure has the focus. The WindowKeyPressFcn doesn't discriminate.

[JIAYING WU]

Same here. gco failed. Btw I'm on Matlab 2019a, not sure if 2019b solved the problem.

[Walter Roberson]

Ah, R2019a has the behavior you mention, and R2019b does not.

At the moment the only thing vaguely relevant I see is https://www.mathworks.com/support/bugreports/details/2027094 about gco and datatips, with a workaround offered for that problem. But it also mentions R2019a Update 5 that I did not know about, so I am installing that now and will report back later.

[Ned]

That result was from matlab online which i'm assuming runs it with 2019b code because it always pops up a warning when I open 2019a apps with it. Also, I'm on the latest version of 2019a.

[Walter Roberson]

I just tested and R2019a Update 5 does not solve the problem.

[Walter Roberson]

Bizzare -- I tested in R2019b a moment ago. Then I had to shut it down in order to install R2019a Update 5. Started up R2019b again, and now it does not give a useful response for gco -- even if I go back into App Designer.

Oh, look at that! gco is reporting about the traditional figure that I have open (or not), not about the App Designer figure! There is nothing in the documentation for gco that suggests that will be the case!!

[Ned]

Looks like they stopped being supported in 2017b.

[JIAYING WU]

lol. Okay now we all know gco is not applicable for app designer. And seems there's no way to return or specify the object on focus in app designer....At least I can't find one.

[Walter Roberson]

Not exactly. Those functions were never supported with uifigures: that documentation is saying that as of R2017b, the supported functionality for uifigures has increased to support most things with those notable exemptions. uifigures started out not supporting much.

[Ned]

Well, it's still not supported.