How to replace HTML resources? #4481

igufei · 2023-04-21T07:40:24Z

igufei
Apr 21, 2023

I want to implement a functionality where I open an HTML webpage, and the HTML content contains the string "hello world". Now, I want to replace this string with "hello cefsharp" before the HTML resource is displayed on the screen. I don't want to use JavaScript injection.

Below is the code I have implemented using IResponseFilter, but it throws an error when the length of dataBytes is greater than 65536. I'm not sure how to resolve this issue. Is there a better way to achieve this?

FilterStatus IResponseFilter.Filter(Stream dataIn, out long dataInRead, Stream dataOut, out long dataOutWritten)
        {
            if (dataIn == null)
            {
                dataInRead = 0;
                dataOutWritten = 0;

                return FilterStatus.Done;
            }
            try
            {
                // 获取内容bytes
                dataInRead = Math.Min(dataIn.Length, dataOut.Length);
                var readBytes = new byte[dataInRead];
                dataIn.Read(readBytes, 0, readBytes.Length);
                // 识别编码
                if (encoding == null)
                {
                    encoding = GetEncodeType(readBytes);
                }
                var data = encoding.GetString(readBytes);
                data = data.Replace("<head>", "<head><style>::-webkit-scrollbar {display: none} body{font-family: 'Microsoft YaHei';}</style>")
                //.Replace("\r", "")
                .Trim();
                var dataBytes = encoding.GetBytes(data);
                if (dataBytes.Length <= 65536)
                {
                    dataOutWritten = dataBytes.Length;
                    dataOut.Write(dataBytes, 0, dataBytes.Length);
                }
                else
                {
                    dataOutWritten = readBytes.Length;
                    dataOut.Write(readBytes, 0, readBytes.Length);
                }

                dataIn.Position = 0;
                dataIn.CopyTo(memoryStream);
                if (dataInRead < dataIn.Length)
                {
                    return FilterStatus.NeedMoreData;
                }

            }
            catch (Exception ex)
            {
                LogHelper.Instance.WriteLog("IResponseFilter.Filter:" + ex.Message);
                dataInRead = 0;
                dataOutWritten = 0;
                memoryStream = null;
            }


            return FilterStatus.Done;
        }

amaitland · 2023-04-24T08:59:53Z

amaitland
Apr 24, 2023
Maintainer

https://github.com/cefsharp/CefSharp/wiki/General-Usage#request-interception

4 replies

igufei Apr 24, 2023
Author

public class CustomResourceRequestHandler : CefSharp.Handler.ResourceRequestHandler
{
	protected override IResourceHandler GetResourceHandler(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, IRequest request)
	{
		//ResourceHandler has many static methods for dealing with Streams, 
		// byte[], files on disk, strings
		// Alternatively ou can inheir from IResourceHandler and implement
		// a custom behaviour that suites your requirements.
		return ResourceHandler.FromString("Welcome to CefSharp!", mimeType: Cef.GetMimeType("html"));
	}
}

This code can indeed replace html, but I want to replace it on the original html

amaitland Apr 26, 2023
Maintainer

If you keep reading you'll see you can implement your own IResourceHandler.

IResponseFilter is tricky to implement, you have to write your data in 64k chunks. There are more examples in the project source.

igufei Apr 26, 2023
Author

thank you

zzzww Aug 14, 2024

Hi igufei,

I also have the problem on same case, would you share the solution to me, thanks.

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