WKWebView ViewportSizing logs [SwiftUI]-CodePudding

In using SwiftUI, the WKWebView loads successfully when implemented within a UIViewRepresentable wrapper. However, the following logs appear in the Debug area of Xcode Version 13.4.1:

[ViewportSizing] maximumViewportInset cannot be larger than frame
[ViewportSizing] minimumViewportInset cannot be larger than frame

How can these logs be resolved?

These logs can be reproduced with the following minimal reproducible example:

WebApp.swift

import SwiftUI
import WebKit

@main
struct WebApp: App {
    var body: some Scene {
        WindowGroup {
            WebView()
        }
    }
}

struct WebView: UIViewRepresentable {
    func makeUIView(context: Context) -> some UIView {
        let webView = WKWebView()
        webView.load(URLRequest(url: URL(string: "https://www.google.com")!))
        
        return webView
    }
    
    func updateUIView(_ uiView: UIViewType, context: Context) {}
}

PROGRESS:

These logs seem to originate from the following WebKit browser engine source code:

maximumViewportInset: https://github.com/WebKit/webkit/blob/main/Source/WebKit/UIProcess/API/Cocoa/WKWebView.mm#L1623
minimumViewportInset: https://github.com/WebKit/webkit/blob/main/Source/WebKit/UIProcess/API/Cocoa/WKWebView.mm#L1638

These logs persist despite commenting out the webView.load(URLRequest(url: URL(string: "https://www.google.com")!)) line. So, it's concludable that it's not a website issue.

CodePudding user response：

Answer

This can be resolved by setting the frame to more than zero by changing this:

let webView = WKWebView()

To this:

let webView = WKWebView(frame: CGRect(x: 0.0, y: 0.0, width: 0.1, height: 0.1))

Explanation

In looking at the WKWebView source code, it appears that the logs are due to the following logic:

Logic that logs [ViewportSizing] maximumViewportInset cannot be larger than frame

auto maximumViewportInsetSize = WebCore::FloatSize(maximumViewportInset.left   maximumViewportInset.right, maximumViewportInset.top   additionalTopInset   maximumViewportInset.bottom);
auto minimumUnobscuredSize = frame - maximumViewportInsetSize;

if (minimumUnobscuredSize.isEmpty()) {
    if (!maximumViewportInsetSize.isEmpty()) {
        ...
        RELEASE_LOG_ERROR(ViewportSizing, "maximumViewportInset cannot be larger than frame");
    }
    ...
}

Logic that logs [ViewportSizing] minimumViewportInset cannot be larger than frame

auto minimumViewportInsetSize = WebCore::FloatSize(minimumViewportInset.left   minimumViewportInset.right, minimumViewportInset.top   additionalTopInset   minimumViewportInset.bottom);
auto maximumUnobscuredSize = frame - minimumViewportInsetSize;

if (maximumUnobscuredSize.isEmpty()) {
    if (!minimumViewportInsetSize.isEmpty()) {
        ...
        RELEASE_LOG_ERROR(ViewportSizing, "minimumViewportInset cannot be larger than frame");
    }
    ...
}

We can inspect these values by adding the following codes in makeUIView:

print("maximumViewportInset: \(webView.maximumViewportInset)")
print("minimumViewportInset: \(webView.minimumViewportInset)")
print("frame: \(webView.frame)")

The outputs are as follows:

maximumViewportInset: UIEdgeInsets(top: 0.0, left: 0.0, bottom: 0.0, right: 0.0)
minimumViewportInset: UIEdgeInsets(top: 0.0, left: 0.0, bottom: 0.0, right: 0.0)
frame: (0.0, 0.0, 0.0, 0.0)

As we can observe, maximumViewportInset, minimumViewportInset, and frame all have values of zeros upon WKWebView() initialization. Hence, the logs are triggered.