Samsung / TizenFX

I develop a Xamarin.Forms application for Tizen TV (6.5), which uses Xamarin.Forms's WebView based on Tizen.WebView. I noticed that some data (cookies, storage data) is cached by the browser for consecutive WebView's launches. I need to clear all cached data in order to make sure that my app uses a 'clear' WebView every time it's launched.

I tried to call following API:

WebView.GetContext().ClearResourceCache();
WebView.GetContext().GetCookieManager().ClearCookies();

but this doesn't work.

Additionally, I tried to manually clear 'chromium-efl' storage:

var dataPath = Application.Current.DirectoryInfo.Data;
Directory.Delete(Path.Combine(dataPath, "chromium-efl"), true);

and it works partially, because cached data is removed, but I have to restart my app. It seems that WebView keeps data in memory.

Finally, I tried to call:
Tizen.WebView.Chromium.Shutdown();
but for some reason, it causes my app to hang.

Questions:

How to clear all WebView's cached data?
How to properly dispose WebView? WebViewRenderer from Xamarin.Forms only calls StopLoading, see https://github.com/xamarin/Xamarin.Forms/blob/5.0.0/Xamarin.Forms.Platform.Tizen/Renderers/WebViewRenderer.cs#L39

For my particular case, calling ewk_context_web_storage_delete_all fixes the issue. I used following extension method:

internal static partial class Interop
{
    private static class Libraries
    {
        internal const string ChromiumEwk = "libchromium-ewk.so";
    }

    internal static partial class ChromiumEwk
    {
        [DllImport(Libraries.ChromiumEwk)]
        internal static extern bool ewk_context_web_storage_delete_all(IntPtr context);
    }
}

public static class ContextExtensions
{
    private static IntPtr GetHandle(this Context context)
    {
        var contextType = context.GetType();
        var handleField = contextType.GetField(
            "_handle",
            BindingFlags.Instance | BindingFlags.NonPublic);
        if (handleField == null)
            throw new NotSupportedException("Context doesn't have a _handle field");
        if (handleField.FieldType != typeof(IntPtr))
            throw new NotSupportedException(
                $"Unexpected field type. Expected {typeof(IntPtr)}, got {handleField.FieldType}");
        return (IntPtr) handleField.GetValue(context);
    }

    public static bool DeleteWebStorage(this Context context)
    {
        var handle = context.GetHandle();
        return Interop.ChromiumEwk.ewk_context_web_storage_delete_all(handle);
    }        
}

Consider to expose this CAPI. Another possible solution for my problem would be to launch a WebView in incognito mode, but I'm not sure if it's exposed now.

The problem seems to be a little bit more complex. It looks like Tizen.WebView was designed to be used as a 'singleton'. I use the AddJavaScriptMessageHandler method (https://github.com/Samsung/TizenFX/blob/master/src/Tizen.WebView/Tizen.WebView/WebView.cs#L432) and this method adds a handler to static _javaScriptMessageHandlerMap dictionary. I don't see any option to remove already registered JS message handler. This is a problem in following case:

create 1st WebView
register JS message handler with some name
destroy 1st WebView
create 2nd WebView
register JS message handler with the same name as for 1st WebView

Second AddJavaScriptMessageHandler call fails due to:

TizenFX/src/Tizen.WebView/Tizen.WebView/WebView.cs

Line 436 in 1909fda

if (_javaScriptMessageHandlerMap.ContainsKey(name))

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[WebView] How to clear all cached data?