How to get previous value before interactions?

[irecsys]

For example,

for one component (such as a bool to indicate visibility of a UI component), the value could be T or F.

When previous value is T, current value is T, a specific action is needed.
When previous value is F, current value is T, another action is needed.

Now, in the callback function, we can only know the current value.

[AIMPED]

@irecsys here an example how to to this:

Creating shapes (annotations) with Patch() method, how to do if no shapes exist in initial fig?

Hi there, I really like the Patch() method but I came a cross an issue. I wanted to add a shape in a figure which does not have a initial shape in it. Problem here is, that the Patch() method does not work as the shape list in the figure layout does not exist. So I can’t use the list specific methods such as extend or append. I tried setting an empty shape list in the initial figure but this is getting interpreted as none by the JS so it throws an error. undefined does not have a method name…