Improve Screenshot API on Windows to allow for WebView screenshots

[hsn-github]

On Windows it is not possible to take a screenshot of the WebView with the code we have currently in the Screenshot API. We might want to consider adding some specialized code for it so that the consuming developer does not see any difference in public API, but the result will be the same.

For a workaround/code that needs to be implemented see this comment below.

---

Original issue:

    bool iscom=  webView.CaptureAsync().IsCompleted;
    var stream = await webView.CaptureAsync();
    using (var fileStream = new FileStream("image.png", FileMode.Create))
    {
        await stream.CopyToAsync(fileStream, ScreenshotFormat.Png, 100);
    }

This code is working fine on Android Phone but on Win Desktop it is returning Blank image and
bool iscom return true in case of Android and on Win Desktop it always return false.

[Eilon]

@hsn-github what is the type of webView? Is it the .NET MAUI WebView, or the platform-specific WebView2 on Windows?

[Eilon]

On Windows you might need to call the WebView2 CapturePreviewAsync method to get a "screenshot" of what's in the webview: https://learn.microsoft.com/en-us/dotnet/api/microsoft.web.webview2.core.corewebview2.capturepreviewasync?view=webview2-dotnet-1.0.1722.45

Hi @hsn-github. We have added the "s/needs-info" label to this issue, which indicates that we have an open question for you before we can take further action. This issue will be closed automatically in 7 days if we do not hear back from you by then - please feel free to re-open it if you come back to this issue after that time.

[hsn-github]

its .net MAUI Webview
e.g. in contentpage or XAML
Webview webView = new Webview();

[jfversluis]

Seems like we might want to consider adding some specialized code for when someone is taking a screenshot of a WebView on Windows. What Eilon was trying to explain is that you need some platform specific code for this. Which would look like this:

string saveImagePath = "image.png";

#if WINDOWS
Stream stream = new FileStream(saveImagePath, FileMode.Create);

await ((MauiWebView)webView.Handler.PlatformView).CoreWebView2
    .CapturePreviewAsync(Microsoft.Web.WebView2.Core.CoreWebView2CapturePreviewImageFormat.Png,
    stream.AsRandomAccessStream());
#else
var stream = await webView.CaptureAsync();

using (var fileStream = new FileStream(saveImagePath, FileMode.Create))
{
    await stream.CopyToAsync(fileStream, ScreenshotFormat.Png, 100);
}
#endif

You can of course do it a bit different if you want, but this should work. A fully working example can be found here: https://github.com/jfversluis/MauiWindowsWebViewScreenshotSample

I will keep this issue around, and edit it a little, to make it into a request for change for the Screenshot API on Windows