Changes in Thunderbird 83

compose

• ComposeAttachment objects now have a size property with the size of the attachment in bytes.

  This change has been backported to Thunderbird 78.5.0.

contacts

• The onUpdated event now calls listeners with a second argument, containing details of the changes made. For example:

  {
    "FirstName": {
      "oldValue": "Daniel",
      "newValue": "Danielle"
    },
    "DisplayName": {
      "oldValue": "Daniel Smith",
      "newValue": "Danielle Smith"
    }
  }
  

menus

• A compose_attachment context can now be used. This context applies when the user opens a context menu on selected attachments in a compose window. The selected attachments can be accessed from the attachments property in an onShown or onClicked listener.

  This change has been backported to Thunderbird 78.5.0.

• The standard properties available to onShown are now available for messages being displayed, if your extension has the messagesRead permission.

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Bugzilla list of fixed WebExtension API defects in Thunderbird 83.