Re: [paymentrequest] Payment instrument installation is platform-dependent (#5)

Somewhat related to: https://github.com/w3c/webpayments/issues/26
(We should consider closing one of these issues)

My suggestion is that we consider the minimum data requirements for registration/installation of a payment app (not a payment instrument) and as a minimum allow websites to request installation of a payment app via the API by supplying that information to a a function like `navigator.payments.registerPaymentApp(...)`.

A call to this API would result in a user prompt to allow the UA to install the payment app. 

On a mobile device, if the user accepts, this could result in the mobile OS appstore getting focus and loading the details of the app that the user wishes to install.

On a desktop device, if the user accepts, this could result in the UA fetching the details of the app from a manifest or similar machine-readable document and registering the payment app in the payment mediator's registered apps database.

What is essential is that the app provide a human-readable name, an icon and the set of payment methods it supports so that when a payment request is received the payment mediator is able to determine if the app can be used to process the request and then to provide the user with a useful app selection dialogue.

This is already implicit in the mobile platform/app pattern but will require some work from desktop browsers to design the payment mediator.

It will also be essential that apps are able to notify the payment mediator if the set of payment methods they support changes.

This can easily be achieved on mobile through app updates but it remains to be discussed how and when a similar process could be achieved on desktop.

---
Reply to this email directly or view it on GitHub:
https://github.com/WICG/paymentrequest/issues/5#issuecomment-163157664