Replay banner does not display in Firefox

[machawk1]

We use Reconstructive for our replay banner (ipwb v0.2018.07.10.1504, 3716d12). It uses Custom Elements for display. Per oduwsdl/MementoEmbed#48 (comment), Custom Elements do not work in Firefox unless a flag is enabled. We can't expect users to do enable this flag for fundamental ipwb functionality. It will work eventually when Firefox supports it without a flag but it remains that there is no graceful degradation for browsers that may never support it.

Chrome 67

Firefox 61

Lets fallback better and allow the replay banner to still be displayed when the browser does not support custom elements.

/cc @ibnesayeed @shawnmjones @phonedude

[machawk1]

Have you tested Reconstructive with a polyfill, @ibnesayeed?

[ibnesayeed]

Banner is not an essential piece of a memento. While having it is useful, but it is more like a value added feature that we can wait for browsers to catch up (and implement Custom Elements). If we really want to make it support Firefox and Edge today, we can add already available polyfills. On the other hand, a more critical piece of functionality that is missing is the ability to rewrite on server-side when we detect that the client does not support Service Worker.

[machawk1]

If we really want to make it support Firefox and Edge today, we can add already available polyfills.

Lets do this.

we detect that the client does not support Service Worker

SWs seem fairly well supported but a check and fallback of displaying the information would be useful and more accessible. With various sites' usage of currency miners in Web Workers, I can imagine a scenario where a client has Workers disabled despite their client supporting the capability.

[ibnesayeed]

Have you tested Reconstructive with a polyfill, @ibnesayeed?

No, I did not, because I was not desperately looking for it to work everywhere. The logic and proof of concept was more important initially than wider support. However, I knew that polyfills for this existed for last few years. Web Component's official site has a happy browser support matrix while CanIUse? suggests about 80% browser market-share already supports it natively.

[ibnesayeed]

Lets do this.

The official polyfill can be found at https://github.com/webcomponents/custom-elements.

[ibnesayeed]

With the public release of Firefox 63 last month, Reconstructive banner now supports it natively. @machawk1 should this issue be closed now?

[machawk1]

Yes.