edit box properties in app designer

Why do you have to set the properties of an app designer edit box object prior to writing text to it for it to render properly? I am trying to display a very long pathname in an edit box of finite width, so I iteratively change the length until a modified version of the filename fits. Here is my code:

function appSetOutputTxt(container, hObject, dspTxt)
s = get(hObject);
% Why do you have to set the edit box properties that you just retrieved in
% order to render text properly?
set(hObject,'FontAngle',s.FontAngle,'FontName',s.FontName,...
    'FontSize',s.FontSize,'FontWeight',s.FontWeight);
lstop=false;
pos=get(hObject,'InnerPosition');
strl=pos(3);
edtlength=ceil(strl);
OutString=string(dspTxt);
strlength=length(dspTxt);
while ~lstop
    hObject.UserData=dspTxt;
    hTest = text(container,'Interpreter','none','Units','pixels',...
        'FontAngle',s.FontAngle,'FontName',s.FontName,...
        'FontSize',s.FontSize,'FontWeight',s.FontWeight,...
        'FontUnits','pixels','String',OutString);
    textExt = get(hTest,'Extent');
    delete(hTest)
    textWidth = ceil(textExt(3)*1.02);
    if textWidth>edtlength
        strlength=strlength-1;
        % if the string is too long, shorten it by one character and try
        % again.
        OutStringStart=dspTxt(1:floor(strlength*1/3)-3);
        OutStringEnd=dspTxt(length(dspTxt)-(floor(strlength*2/3)-1):length(dspTxt));
        OutString=strcat(OutStringStart,'...',OutStringEnd);
    else
        lstop=true;
    end
end
set(hObject,'Value',OutString,...
    'FontAngle',s.FontAngle,'FontName',s.FontName,...
    'FontSize',s.FontSize,'FontWeight',s.FontWeight);

container is an axes object within the app. hObject is the edit box. dspTxt is the full filename we are resizing.

Example:

We start with a filename 'C:\windows\user\someuser\images\savedimages\example\longpath\image.png' and you end up with something like 'C:\windows\...mple\longpath\image.png'

The text doesn't render properly unless the properties that you retrieve with s = get(hObject) are set with the set command. I don't understand why.

[Luna]

Where do you call appSetOutputTxt function in your app?

[Thomas]

It is in the CallBack for pushing a button (ButtonPushedFcn). I call the function on line 72 (within another custom defined function). The CallBack is defined starting on line 82. I have done nothing to alter what order these functions appear in code. App Designer is placing them when I add a private function, for instance.

[Thomas]

I thought I had the work around with the set command early, but I was wrong. I have to run the function twice for it to set the text properly in the edit box.

[Thomas]

It seems as though my problem is with the following code

textExt = get(hTest,'Extent');

On the first run when the app is executed, this gives some strange answers. I added the following bit to the while loop above to generate the answers below...

    if ~lstop
        writestring = [writestring, num2str(textWidth) ', '];
    else
        writestring = [writestring, num2str(textWidth)];
    end

textWidth = 1069, 1061, 1061, 1047, 1040, 1040, 1026, 1023, 1023, 1013, 1005, 1005, 992, 982, 982, 963, 954, 954, 943, 940, 883, 922, 919, 919, 901, 892, 892, 876, 872, 820

So, even though the string gets smaller, the width of the text box gets bigger. (883 length to 922 for example)

The second run makes more sense and performs as expected.

1005, 997, 997, 984, 977, 977, 964, 961, 961, 951, 944, 944, 932, 922, 922, 904, 896, 896, 886, 883, 883, 866, 862, 862, 846, 839, 839, 823

The second time through with the same string (just running the function above from my original question twice) always produces a string that is equal or decreasing in length. Something funky is going on with units or properties here, and I don't know what.