WPF - WritableBitmapRenderHandle.CreateOrUpdateBitmap possible lock contention

• Environment Information

  • CefSharp WPF v86.0.241
  • Windows 10 x64
  • .Net Framework v4.8

• Issue Description
  Drag and drop functionality of a web page running React DnD (https://react-dnd.github.io/react-dnd) causes the entire application running the browser to hang in semi rare cases (never recovering). Stack tracing with dotTrace reveals a possible lock contention in the WPF library, specifically at the CefSharp.WPF.Rendering.WritableBitmapRenderHandle.CreateOrUpdateBitmap() method.

• Steps to reproduce

  • Navigate to a web page that has internal drag and drop functionality (aka. it is possible to drag and drop content within the web page), preferably a web page that uses React DnD in the backend to handle dragging.
  • Drag and drop content within the web page repeatedly.
  • In some cases this should then hang and leave the browser unresponsive.

• Additional Information

  • The script (TypeScript) that handles dragging in our case: https://pastebin.com/VnaME63a (somewhat obfuscated for IP reasons)
  • dotTrace of the suspected lock contention:
    

[amaitland]

I'm not familiar with dotTrace so your screenshots are largely meaningless to me. Are you saying there's a deadlock? Which line exactly? (Link to the source on GitHub please).

---

You can integrate CEF into your apps existing message loop to avoid locking.

https://github.com/cefsharp/CefSharp/wiki/General-Usage#multithreadedmessageloop
You can modify the source to see a demo https://github.com/cefsharp/CefSharp/blob/cefsharp/88/CefSharp.Wpf.Example/App.xaml.cs#L28

The deadlock reported by dotTrace occurs in the WritableBitmapRenderHandler.CreateOrUpdateBitmap(), a method which contains two locks (the later dispatched from within the former):

CefSharp/CefSharp.Wpf/Rendering/WritableBitmapRenderHandler.cs

Line 46 in 516de14

lock (lockObject)

CefSharp/CefSharp.Wpf/Rendering/WritableBitmapRenderHandler.cs

Line 79 in 516de14

lock (lockObject)

Judging by the mention of a Dispatcher in the dotTrace stack trace:

The later lock invoked on row 79 seems to be the origin.

[amaitland]

WritableBitmapRenderHandler.CreateOrUpdateBitmap(), a method which contains two locks (the later dispatched from within the former):

Effectively they're two different functions called on different threads, one if them is just anonymous inline function.

Pull requests welcome.

[amaitland]

See #2275 (comment) for details on one of the other rendering implentations, this might be another alternative.

[amaitland]

Closing as this has been inactive for some time. No other reports have been received.

If this reproduces with the current supported version then this can be reopened.