Return of handle, which was selected with 'ButtonDownFcn'

Hey there,

I plotted some data in just one figure, after that, I want to select some plots by mouse in the figure and I want to highlight it by increasing the 'LineWidth' and get the information, which of the plotted object has been selected.

In my main script, I use the following code to call the function (dxf.handle contains all the handles, which have been plotted before):

selected_entities = sub_select(dxf.handle);

Unable to resolve the name 'dxf.handle'.

The function has the following code:

function selected_object = sub_select(H)
set(H, 'ButtonDownFcn', selected_object = @LineSelected)
end

function ObjectH = LineSelected(ObjectH, EventData)
set(ObjectH, 'LineWidth', 2.5);
end

In general the code works and it's possible to highlight the objects, but I didn't get the information, which handle was selected. This information should be stored in selected_entities. At the moment, I just get this:

selected_object = @LineSelected

Thanks in advance for your help.

Best regards

Daniel

Answer 1

[Walter Roberson]

function selected_object = sub_select(H)
set(H, 'ButtonDownFcn', selected_object = @LineSelected)
end

That code attempts to call

set(H, 'ButtonDownFcn', 'selected_object', '@LineSelected')

which is going to fail because '@LineSelected' is not a name-value pair.

If you were to use

function selected_object = sub_select(H)
set(H, 'ButtonDownFcn', 'selected_object = @LineSelected')
end

then that might not be rejected immediately, but it also would not work: text entries for functions are evaluated in the base workspace, so selected_object would be set in the base workspace, where it would not be available to be returned by the sub_select function.

You have the further issue that you expect sub_select to return the selected object, but sub_select is instead just setting the button down fnc callback (which will be invoked at some later point.)

You would have to do something like have sub_select set the button down function, and then uiwait or waitfor some property to be changed, and then pull out the value of that property.

[Daniel Ludwig]

Hi Walter,

thanks for your reply, I unterstand.

Do you have any idea, how to "pull out the value"?

[Walter Roberson]

function selected_object = sub_select(H)
    ax = ancestor(H(1), 'axes');
    ax.UserData = [];
    set(H, 'ButtonDownFcn', @(src,~) set(ax.UserData, src));
    waitfor(ax, 'UserData');
    selected_object = ax.UserData;
    set(H, 'ButtonDownFcn', '')
end