Maybe another way to put the question is, "when an axes object is deleted, is there any documented guarantee of what order subordinate things get deleted in"? Should its children (e.g., text boxes) always be deleted before its property content (e.g., UserData)?
Matlab 2014b: graphics object deletion
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I am comparing the behavior of the test code below in both R2013b and R2014b. In R2013b, running test.m results in the message 'User Data Present' being printed to the screen. However, when I run the very same code in R2014b, the message 'No User Data' is printed. Can anyone reproduce this and explain why the results are different?
function test
imagesc(ones(100));
options = {'The Text','HorizontalAlignment', 'center',...
'color' , 'yellow','HitTest','off',...
'DeleteFcn',@MyDelete};
text(50,50,options{:});
set(gca,'UserData','User Data Present');
close(gcf)
function MyDelete(~,~)
d=get(gca,'UserData');
if isempty(d)
disp('No User Data')
else
disp(d)
end
Accepted Answer
Rich Ohman
on 21 Nov 2014
It is generally not safe to use gcf, gca, and gca in a callback function since these are both user-settable and could be modified internally if interrupted by another callback. You should use gcbo or gcbf to get the current object or current figure from within a callback function.
If you replace the MyDelete function with the following code, you will get the correct behavior:
function MyDelete(~,~)
obj = gcbo;
ax = get(obj,'Parent');
d=get(ax,'UserData');
if isempty(d)
disp('No User Data')
else
disp(d)
end
3 Comments
Rich Ohman
on 21 Nov 2014
Remember that gca creates a new axes if it cannot use the figure's CurrentAxes property value. In this case, the original axes is being destroyed, so gca created a new one. This is why the UserData was empty, the default value for a new axes.
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