AppDesinger Expand UI Tree Node not always working

Using AppDesinger we are creating a tree node with checks. In our startup function of the AppDesigner we want the node to be expanded. However, the framework due to loading issues sometimes expands the tree node, sometimes it does not. This is frustrating and customer pain.

Example: (left bad behaviour, right correct behaviour)

Initalized, but Run All node did not expand Initialized and fully expaneded, as desired

As I understood the GUI initialization is somehow asynchronous, hence we added a timer in the end of the startup function. Yet, the problem persists SOMETIMES.

End of the startupFcn in AppDesinger

% Refresh the display of tree nodes to reflect initial counts and status icons.
reload_nodes(app, app.Tree)
drawnow;
% ------------------------------------------------------------
% ASYNC: Expand tree AFTER UI created all nodes
% ------------------------------------------------------------

% Expand the main 'Run All' node to show all sub-checks by default.
app.ExpansionTimer = timer( ...
    'StartDelay', 1.0, ...            % short delay so UI event queue finishes
    'ExecutionMode', 'singleShot', ... % only run once
    'BusyMode', 'queue', ...           % ensures execution is queued
    'TimerFcn', @(~,~) expand_tree_async(app) ...
    );
start(app.ExpansionTimer);

The expand_tree_async Function that is called.

function expand_tree_async(app)
% expand_tree_async Expand the main tree node after UI rendering completes.
%
% This function is called asynchronously from a timer after the tree nodes
% have been created and rendered. Some UI components in App Designer are
% constructed asynchronously, so expanding tree nodes immediately after
% reload does not always work on the first try. By running this function
% on a short delay, the function ensures that all tree nodes exist before
% calling EXPAND on the main 'Run All' node.
%
% The function also performs basic validity checks and cleans up the timer
% handle used to invoke the expansion.
try
    % Make sure the node exists
    if isvalid(app.RunAllNode)
        expand(app.RunAllNode, 'all');  % Expand all categories
        drawnow;                        % Force UI update
    end
catch
    % ignore errors (e.g. app closed)
end
% Clean up the timer so MATLAB doesn't leak handles
try
    if ~isempty(app.ExpansionTimer) && isvalid(app.ExpansionTimer)
        stop(app.ExpansionTimer);
        delete(app.ExpansionTimer);
    end
catch
end
app.ExpansionTimer = [];
% Clean up the Progress Dialog
try
    if isvalid(app.StartUpProgressBar)
        drawnow;
        delete(app.StartUpProgressBar);
    end
catch
end
app.StartUpProgressBar = [];
end

Is there something I am missing, or how can consistent loading and expanding of the UI Interface be safely done? Thank you.

[dpb]

try
    % Make sure the node exists
    if isvalid(app.RunAllNode)
        expand(app.RunAllNode, 'all');  % Expand all categories
        drawnow;                        % Force UI update
    end
catch
    % ignore errors (e.g. app closed)
end

Your try-catch block doesn't even tell you if isvalid() fails -- if, for some reason that is not True on these odd occurrences, then you would see the symptoms you do.

Why that might be so, I don't know, but at least while you're trying to track this down have some way of knowing that the expand() call didn't occur. As a patch, I'd add a MsgBox warning popup and then probably a waitfor or just a pause and try again.

Similarily, if the catch block executes for some reason and you ignore everything, then a valid error that prevented the expansion is being ignored and you don't know about it -- again, until you can discover what is actually happening here you need to be able to know what occurs on every possible path in order to be able to take whatever action(s) is(are) needed.

Answer 1

[dpb]

app.ExpansionTimer = timer( ...
    'StartDelay', 1.0, ...            % short delay so UI event queue finishes
    'ExecutionMode', 'singleShot', ... % only run once
    'BusyMode', 'queue', ...           % ensures execution is queued
    'TimerFcn', @(~,~) expand_tree_async(app) ...
    );

is your assignment of the callback function, but expand_tree_async expects the app object argument.

The timer event passes the timer object and which event id; not the app and having app in the argument list doesn't refer to the global app struct; you need to pass it as an additional argument so the callback function has access to it.

Use

function expand_tree_async(~,~,app)

as the callback function prototype and then

app.ExpansionTimer = timer( ...
    'StartDelay', 1.0, ...            % short delay so UI event queue finishes
    'ExecutionMode', 'singleShot', ... % only run once
    'BusyMode', 'queue', ...           % ensures execution is queued
    'TimerFcn', {@expand_tree_async,app} ...
    );

instead so the app object is actually passed.

[Ravindra Goyal]

Thank you dpb! The app object is passed with the previous logic also, I feel the object instatiation we do also in the startup is too computational heavy. We moved all heavy non UI work into the timer function. This seems to work, yet a full understanding on our side as to why some PCs render it smoothly (the faster ones) and why do not (the slower ones) we can not gain,.