[wadetandy]

My understanding is that the reason Chrome has to use the iOS webkit view is because that's the only way to get JIT javascript compilation working for apps submitted to the app store. Does anyone have a sense of whether it would be possible to switch to Blink and V8 with a locally compiled and sideloaded version of the app? Would there be any benefit?

[zwily]

You're not allowed to provide your own web render engine at all. The JIT issue was solved a couple versions of iOS ago - embedded webviews now get JIT just like Safari.

[DonHopkins]

It's my understanding that only embedded WKWebViews are allowed to enable the JIT compiler, but not UIWebViews (or in-process JavaScriptCore engines). WKWebView is an out-of-process web browser that uses IOSurface [1] to project the image into your embedding application and IPC to send messages.

So WKWebView's dynamically generated code is running safely firewalled in a separate address space controlled by Apple and not accessible to your app, while older UIWebViews run in the address space of your application, and aren't allowed to write to code pages, so their JIT compiler is disabled.

Since it's running in another process, WkWebView's JavaScriptEngine lacks the ability to expose your own Objective C classes to JavaScript so they can be called directly [2], but it does include a less efficient way of adding script message handlers that call back to Objective C code via IPC [3].

[1] https://developer.apple.com/reference/iosurface

[2] https://developer.apple.com/reference/javascriptcore/jsexpor...

[3] https://developer.apple.com/reference/webkit/wkusercontentco...

[eslaught]

> You're not allowed to provide your own web render engine at all.

Is that true? I understand the security argument against JITs, but I don't see why it would be objectionable to run a copy of e.g. Gecko if you excluded the JS JIT component. (Of course you would never actually do that. But I'm trying to tease apart the separate arguments and see if they're actually connected.)

It seems to me that the root cause for this is all the JIT. If the JIT in iOS has to be exposed via IPC for security (as claimed in a sibling comment) it's simply not going to be a win to try to use it in combination with a separate rendering engine, if it's even possible at all.

[therealmarv]

take a close look at Opera Mini ;) (they are doing Server rendering)

[bad_user]

Before iOS 9 (or something) that JIT engine wasn't even exposed in the web view available for apps, so no matter what you did, you couldn't match the performance of Safari.

On iOS browsers like Chrome and Firefox are basically unable to compete in terms of performance, web standards or features like browser plugins. So people that use them do so just to get sync. Of course Safari Mobile is decent nowadays, but that's not the issue.

[oatmealsnap]

Yea, it was always an outdated version of WebKit.

[spikengineer]

If you don't use Apple Webkit view apple doesn't even allow you put your browser on the appstore. All other browser engines are banned.

See section 2.5.6 of the Appstore guidelines

"2.5.6 Apps that browse the web must use the appropriate WebKit framework and WebKit Javascript."

https://developer.apple.com/app-store/review/guidelines/

[rweichler]

No. You can't map executable pages in the sandbox. JITs (such as LuaJIT) only work while the debugger is attached (i.e., you open the app by clicking "run" in Xcode).

[therealmarv]

Opera Mini bypasses this restriction with doing Server Rendering. I wonder why Apple is ok with them (because it'a a big security risk to server render HTTPS IMHO).

And regarding your quesiton: I'm sure you cannot replace their webkit usage with one switch to Blink... I'm sure the iOS internal webview is deeply integrated/

[abrowne]

Opera Mini, the app, is not rendering HTML as you say. They don't block VNC or RDP apps even though you can run a remote browser through them.

[oatmealsnap]

That might allow Chrome Extensions on iOS, but it seems like a lot of work to make that happen.

[madeofpalk]

> locally compiled

You can't "locally compile" code on iOS. That's against App Store guidelines.

[hawski]

I am sure that he meant "locally" as on one's one computer without AppStore.