Issues with callbacks and large handle structures?

I am working on a gui, and encountered a strange problem. When I pass 'h' to a uicontrol callback and put a breakpoint in the callback, I find that only the first 30 handles are present in the callback instance of 'h'. (i.e. h.figure, h.CCUpanel, h.gammacontrol, etc.)

Since the callback was called by a later uicontrol, errors were generated when I attempted to refer to it.

Has anyone seen this before and/or know how to correct it or work around it?

Thanks, Sean

[Jan]

It is impossible to know the reason without seeing the code, Perhaps you have defined the callback function such, that it contains the only partially created handles struct? Then use the function GUIDATA to get the most recent value.

[Sven]

I agree with Jan, and I can almost guarantee the following:

If you can replicate your problem in a *small* function (ie, with all unnecessary code removed so that it has only code that causes issues), you will actually find and fix the problem before we do.

[Image Analyst]

Perhaps you're only seeing part of it in the popup window when you hover over it but if you type handles into the command window or look at it in the variable editor you will see the rest of the members. Is that a possibility? Either that or like the others said you added members to handles but didn't do anything to make sure those additions are kept around for the next function that expects to see them.

[Sean]

Thank you all...

Jan is correct. Apparently I am only passing a partial handle struct to the callback. I didn't realize that it hardened the input variables when the callback was set (as opposed to sending the designated variables at time of activation).

Jan... If you formally answer, I will accept it.

Also, does anyone know how to set a pointer to the handle structure as an input to a callback (so that a dynamic structure can be used)?

Thanks,

Sean

Answer 1

[Jan]

It is impossible to know the reason without seeing the code. Perhaps you have defined the callback function such, that it contains the only partially created handles struct? Then using the function GUIDATA is equivalent to using a pointer to the handles struct:

% Create the figure and the handles struct:
handles.DlgH = figure;

% Pass an incomplete handles struct:
uicontrol('Style', 'pushbutton', 'Callback', {@Callback, handles});

% Callback function:
function Callback(ObjH, EventData, handles)  % handles is incomplete!
handles = guidata(handles.DlgH);  % handles is complete and uptodate
...
handles.MyData = clock;
guidata(handles);

I'd prefer the following to avoid using the incomplet handles struct:

... 'Callback', {@Callback, DlgH}
...
function Callback(ObjH, EventData, DlgH)