Re: [webpayments] How are payment instruments registered? (#14)

@rsolomakhin The most concerning part of the installability section of the Web App manifest spec is the following:

> How a user agent makes use of these installability signals to determine if a web application can be installed is left to implementers.

In general, I'm a bit wary of the whole 'payment instrument as app manifest' approach because there is no trigger that a site can call to be sure that the payment instrument was installed. I'm also not sure what the polyfill story for manifest-based payment instruments are.

So, a few questions:

1. What are the upsides and downsides to a manifest-based approach?
2. How does a site that issues payment instruments know if a payment instrument has been installed (or is available)?
3. How would a manifest-based approach be polyfilled?

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/webpayments/issues/14#issuecomment-161508394