Thunderbird/Add-ons Guide 63

Add-ons Guide for Thunderbird 63 and beyond

(First Draft)

The picture beyond Thunderbird version 60 is rather uncertain, given the continued high rate of change in Firefox platform code. We will work with add-on authors in the coming months to determine a viable post-60 add-on strategy. Here are some general thoughts.

• Work has been undertaken to keep supporting legacy add-ons "somewhat" in Thunderbird 63 and beyond. We implemented an overlay loader that will load XUL overlays for add-ons but may cause graphical glitches or malfunctions. We're tracking this in bug 1476259.

• Legacy add-ons must replace install.rdf file with a WebExtensions style manifest.json file, which includes the key "legacy" set to true. See Lightning as an example https://hg.mozilla.org/comm-central/rev/e81f4b59a00a7d3e18d50fd3851ecbd47762a186#l2.5.
  • Note: The @variables@ are build variables, add-ons need to use fixed strings.
    
  • Note: This only holds for XUL Overlay legacy extensions. Bootstrapped legacy extensions continue to work without a manifest.json file and will in fact break if you add that file.

• The general idea for TB 68 ESR will be to make add-ons restartless, although the replacement for restartless add-ons in TB 68 isn't yet clear, or to WebExtensions, where we still have to define the interface. Further reading on restartless add-ons:
  • https://mail.mozilla.org/pipermail/firefox-dev/2018-June/006503.html
  • https://mail.mozilla.org/pipermail/firefox-dev/2018-June/006507.html
  • https://bugzilla.mozilla.org/show_bug.cgi?id=1413432#c7

Removed in mozilla63

• XUL element listbox together with listboxitem and listcell. -- Replacement: richlistbox.