Host set with SetVirtualHostName within WebMessageReceived event handler isn't recognized #2456

zspitz · 2022-05-13T08:31:43Z

Description
I'm trying to use SetVirtualHostNameToFolderMapping to map a host name to a local folder, from within a WebMessageReceived event handler. If I then create an image within the webview with an src referencing the mapped hostname, the mapping is ignored, and DevTools console displays: Failed to load resource: net::ERR_NAME_NOT_RESOLVED.

Version
SDK: 1.0.1248-prerelease
Runtime: 101.0.1210.39 (Official build) (64-bit)
Framework: WPF
OS: Windows 10 Home 21H2 (build 19044.1706)

Repro Steps

Call postMessage from JavaScript within the webview.
In the handler WebMessageReceived, call SetVirtualHostNameToFolderMapping
In the mesage event listener, set the src of an image to something in the mapped host folder.

Additional context

Project illustrating the problem: _testWebviewDialogs.zip

SO question

XAML:

<Window x:Class="_testWebviewDialogs.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:wv="clr-namespace:Microsoft.Web.WebView2.Wpf;assembly=Microsoft.Web.WebView2.Wpf">
    <wv:WebView2 x:Name="webview" />
</Window>

Code behind:

using System.IO;
using System.Threading.Tasks;
using System.Windows;
using Microsoft.Web.WebView2.Core;

namespace _testWebviewDialogs;
public partial class MainWindow : Window {
    public MainWindow() {
        InitializeComponent();
        Loaded += async (s, e) => await initializeAsync();
    }

    private async Task initializeAsync() {
        await webview.EnsureCoreWebView2Async();
        webview.CoreWebView2.WebMessageReceived += (s, e) => {
            webview.CoreWebView2.SetVirtualHostNameToFolderMapping(
                "assets",
                @"C:\path\to\folder",
                CoreWebView2HostResourceAccessKind.Allow
            );
            webview.CoreWebView2.PostWebMessageAsString(@"breakpoint.bmp");
        };

        var html = await File.ReadAllTextAsync("container.html");
        webview.NavigateToString(html);
    }
}

container.html:

<!DOCTYPE html>
<html>
<body>
    <button id="button1">Click me</button>
    <img id ="img1" src="" />
    <script>
        document.getElementById("button1").addEventListener('click', ev => {
            chrome.webview.postMessage('source');
        });
        window.chrome.webview.addEventListener('message', event => {
            document.getElementById('img1').src = `https://assets/${event.data}`;
        });
    </script>
</body>
</html>

The text was updated successfully, but these errors were encountered:

champnic · 2022-05-13T19:12:32Z

Hey @zspitz - thanks for the bug report!

This limitation is currently expected when using SetVirtualHostNameToFolderMapping:
"As the resource loaders for the current page might have already been created and running, changes to the mapping might not be applied to the current page and a reload of the page is needed to apply the new mapping."
From: https://docs.microsoft.com/en-us/dotnet/api/microsoft.web.webview2.core.corewebview2.setvirtualhostnametofoldermapping?view=webview2-dotnet-1.0.1210.39#remarks

If you reload the page first, or set the mapping before navigating to your page, does the mapping work as expected?

zspitz · 2022-05-15T09:04:15Z

@champnic I know that setting the mapping before navigation works; and reloading would also probably work. But the virtual host target path may change multiple times over the lifetime of the application, and I don't really want to reload each time.

But instead of removing and recreating the virtual host path, I can create (and recreate) a symbolic link to the target path as needed. Then, at application start, I can map the virtual host to the symbolic link:

var symlinkPath =
    Path.Combine(
        Path.GetDirectoryName(
            Assembly.GetExecutingAssembly().Location!
        )!,
        "assets"
    );

// In order to map the virtual host name, the directory has to exist
// Creating a dummy folder here
Directory.CreateDirectory(symlinkPath);

webview.CoreWebView2.SetVirtualHostNameToFolderMapping(
    "assets",
    symlinkPath,
    CoreWebView2HostResourceAccessKind.Allow
);

webview.CoreWebView2.WebMessageReceived += (s, e) => {
    Directory.Delete(symlinkPath);
    Directory.CreateSymbolicLink(symlinkPath, @"C:\Users\Spitz\Desktop\testmd");
    webview.CoreWebView2.PostWebMessageAsString(@"breakpoint.bmp");
};

zspitz added the bug Something isn't working label May 13, 2022

victorthoang assigned champnic May 13, 2022

champnic closed this as completed May 13, 2022

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Host set with SetVirtualHostName within WebMessageReceived event handler isn't recognized #2456

Host set with SetVirtualHostName within WebMessageReceived event handler isn't recognized #2456

zspitz commented May 13, 2022 •

edited

champnic commented May 13, 2022

zspitz commented May 15, 2022 •

edited

Host set with SetVirtualHostName within WebMessageReceived event handler isn't recognized #2456

Host set with SetVirtualHostName within WebMessageReceived event handler isn't recognized #2456

Comments

zspitz commented May 13, 2022 • edited

champnic commented May 13, 2022

zspitz commented May 15, 2022 • edited

zspitz commented May 13, 2022 •

edited

zspitz commented May 15, 2022 •

edited