ios: fix app flickers on start

[shonsirsha]

Fixing it by adding a check in WebView.swift for a message
sent from the react app signaling react app is ready.

On ready, it reveals the webview smoothly with transition.

[shonsirsha]

PTAL @benma

[shonsirsha]

Instead of using an arbitrary-valued delay, here we're checking for reactAppReady property instead. Check runs recursively until that value is set to true (with max retry).

This property is set by the useAppReady hook from the react app. cc @benma

[benma]

Nice!

Instead of polling, please call directly into Swift. See this as an example where TS is calling goCall(), and the call is handled in Swift:

bitbox-wallet-app/frontends/ios/BitBoxApp/BitBoxApp/WebView.swift

Line 109 in 9ef6c60

contentController.add(bridge, name: "goCall")

This would be better as it requires fewer calls and has an even smaller delay until ready. When the react app is ready, tell Swift to transition.

[benma]

(see comment)

[shonsirsha]

@benma , PTAL thanks a lot for the review!

[benma]

Would it make sense to add a fallback?

useEffect(() => {
     const timer = setTimeout(() => {
        /* send appReady */ 
     }, 3000); 
     return () => clearTimeout(timer);

Just in case there is some weird delay in getting accounts and devices results.

Otherwise code looks good, I'll test it on a device tomorrow.

[shonsirsha]

Okay - added the fallback to call regardless of the devices || accounts results.

[shonsirsha]

@benma thanks 👍 PTAL (also rebased).

[benma]

Unfortunately it does not work for me, WebView.swift never gets the appReady message and the webview stays invisible.

[shonsirsha]

Unfortunately it does not work for me, WebView.swift never gets the appReady message and the webview stays invisible.

I think it may be the postMessage()- I made an update which was wrong.

[shonsirsha]

@benma , thanks for the review. Fixed the bug and simplified the hooks. PTAL 🙏