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xlim listener for zoom reset and linkaxes strange behavior

16 vues (au cours des 30 derniers jours)
Jim Hokanson
Jim Hokanson le 26 Nov 2017
Commenté : Jim Hokanson le 15 Avr 2021
I've attached a 'XLim' listener to an axes object.
I had been previously using a timer due to issues with catching the events appropriately (for reasons I can't exactly remember). Now they're starting to come back to me ...
Here's some basic test code (from 2017b):
ax = gca;
L1 = addlistener(ax, 'XLim', 'PostSet', @(x,y)disp(y.AffectedObject.XLim));
When I zoom in my listener fires properly. However, when I double-click to reset the zoom (or right click and reset) no listener is fired! The 'XLim' property clearly changed but Matlab doesn't seem to care to inform me of this fact.
This seems like a bug to me. Looking at SO there is a suggestion that I listen to the zoom callback, but I'd rather not touch any callbacks since I might need 2 or more callbacks for a single axes.
Even more surprising is that by linking the axes an event is now fired on resetting the zoom. This seems to persist even if I turn the linking off.
ax = gca;
L1 = addlistener(ax, 'XLim', 'PostSet', @(x,y)disp(y.AffectedObject.XLim));
linkaxes(ax,'x') %reset works as desired
linkaxes(ax,'x','off') %reset still works as desired
Questions are:
  1. How can I get a listener event for zoom reset (and pan reset) that is resistant to accidental overwriting (i.e. most likely by avoiding a single callback property)
  2. If the behavior is not a bug, why? See remark below on blog post.
  3. Why does running linkaxes fix this problem?
  4. Is there a way of accomplishing whatever the linkaxes function is doing without actually needing to modify the linkaxes behavior of the axes?
The following blog post comes to mind but it seems like a reset-zoom should trigger an event. In the linked example plotting new data that expands the x-limits doesn't throw an event. https://blogs.mathworks.com/loren/2015/12/14/axes-limits-scream-louder-i-cant-hear-you/
If you plot again the event stops getting thrown in response to resetting the zoom. ¯\_(ツ)_/¯
ax = gca;
L1 = addlistener(ax, 'XLim', 'PostSet', @(x,y)disp(y.AffectedObject.XLim));
plot(1:100) %reset not working as desired

Réponse acceptée

Jim Hokanson
Jim Hokanson le 27 Nov 2017
Modifié(e) : Jim Hokanson le 27 Nov 2017
It turns out that there is a lot of publicly readable code behind linkaxes, or really, linkprop. After some debugging I discovered the MarkedClean event. More info on this interesting event can be found at: https://undocumentedmatlab.com/blog/undocumented-hg2-graphics-events
I now have the following code:
%Updated to point to XRuler instead of just axes_handle
%per Yair's recommendation
obj.L3 = ...
addlistener(axes_handle.XRuler,'MarkedClean',@(~,~) obj.cleanListen);
function cleanListen(obj)
if isequal(obj.xlim,get(obj.axes_handle,'XLim'))
It seems like MarkedClean is perhaps one of the ultimate 'Always tell me about things' events.
I'm not entirely sure what the answers to my questions are, but this serves as a decent workaround for what I need.
  3 commentaires
Jim Hokanson
Jim Hokanson le 27 Nov 2017
Thanks Yair. I'm not familiar with XRuler but a quick search turned up this info from your site:
Yair Altman
Yair Altman le 27 Nov 2017
of course, where else? :-)

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Plus de réponses (1)

Adam Danz
Adam Danz le 15 Avr 2021
Starting in r2021a, you can supply a LimitsChangedFcn function the x-axes (or any of the x/y/z axes). This callback function overcomes the problems described with the XLim change event listener.
Specifically, the LimitsChangedFcn overcomes the problem mentioned by OP: "when I double-click to reset the zoom (or right click and reset) no listener is fired!"


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