Proposal: MailExtensions API to allow UI overlays, but no script injection

Philipp Kewisch kewisch at
Sat Oct 12 13:42:19 UTC 2019

> On 12. Oct 2019, at 2:56 PM, ace <acelists at> wrote:
> Dňa 12. 10. 2019 o 14:41 Philipp Kewisch napísal(a):
>>>> On 12. Oct 2019, at 12:55 PM, ace <acelists at> wrote:
>>> Hi. We recently added a feature in Thundebird that allows addons to
>>> listen when specific windows are opened (by specifying document URLs
>>> they are interested in). When that happens, the addon specified code can
>>> run on that window. Then you could change the appearance of UI elements
>>> using standard DOM methods, instead of a XUL overlay file.
>>> See registerWindowListener() at
>>> This could cover some of the addon use-cases.
>>> aceman
>> Note this api isn't available to MailExtensions, just the experiments.
> Thanks for the info. Surely it could be added to the MailExtensions API
> to expose it to WE addons, as it is actually intended to be used by
> addons? We use it e.g. for the mozmill addon.
We do because we have it now, but it would be too broad access to fit into the concepts WebExtensions can provide. You wouldn't have an api that gives arbitrary access to window load events, you'd have an api that allows manipulating specific parts of the windows.


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