Observe graphics object added to the axes

I have an axes object which contains several child objects (lines, patches, etc.). I have a function which sets the callback function for these objects. What I want is that whenever the user adds another object to the axes, an event is activated and sets the callback for the newly added object. My idea was to look when the number of the children of axes grow as it indicates a new object. Unfortunately, axes.Children is not a SetObservable property, so listeners cannot be attached to the axes object. Any ideas how to solve this problem?

Answer 1

[Roman Müller-Hainbach]

Maybe the 'LegendableObjectsUpdated' event could be used for your purposes. I retrieved this from

events('matlab.graphics.axis.Axes')

[Jan Kappen]

This does not work anymore, since most of the events are hidden.

Workaround:

m = ?matlab.graphics.axis.Axes;
e = m.EventList

Try it out, there are tons of events.

[Zoltán Csáti]

Thank you. I will try it out once I have access to MATLAB. On this computer, I don't have a license, and on the other computer, I have R2015b. The poor backward compatibility in MATLAB is a pity...

Answer 2

[uno]

You can use a wrapper to change an observable property every time you plot

function main()
    ax = axes;
    propListener = addlistener(ax, 'UserData', 'PostSet', @(src,evnt)mycallback(evnt.AffectedObject)); % Attach the callback to the UserData property
    myplot(ax,1,1) % Wrapper of plot(), 1st argument must be the target
end

function mycallback(ax)
    % Do something with ax.Children
end

function myplot(varargin) % Wrapper function
    plot(varargin{:});
    varargin{1}.UserData = 1; % Overwrite UserData to trigger the listener event
end

Or just ditch the callbacks entirely and save yourself a lot of troubles..

function myplot(varargin)
    h = plot(varargin{:});
    % Do something with the new objects
end