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Cells and windows

Cells and window objects can also emit events and there is no need in cloning event objects to assign multiple handlers (it is done automatically once an EventHandler method is applied).

Cells​

There are following functions are available to extract cell objects RemoteCellObj from the evaluation context

There are following patterns available to attach handlers

  • "Destroy"
  • "State"
  • "Error"

The most practical one is the first one

With[{},
  EventHandler[ResultCell[], {"Destroy" -> (Print["Destroyed!"] &)}];
  "Lovely day"
]

try to reevaluate it multiple times

It can be used to unsubscribe from listeners, stop tasks once a cell has been reevaluated or destroyed.

info

Cell events are supported for all types of cells including WLX, Slides, and etc.

info

Cell events are working as well for projected outputs to new windows

Window​

A WindowObj represents a current window, where the notebook is running. Usually it is used in FrontFetch, FrontSubmit, however it also supports a few patterns for handlers

  • "Closed"
tip

Use "Closed" event to remove tasks running in the background

example

test = {0,1,0};

EventHandler[CurrentWindow[], {"Closed" -> Function[Null,
  test = {1,0,0};
]}];

Graphics[{RGBColor[test // Offload], Disk[{0,0}, 1]}]

Try to reload a page / window and see the changes.

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