Whilst the Windows Forms Out-Of-Process Designer (or the OOP designer) is by far and large sort of a black box to the users, it actually provides some good means to find out more information on its state.
Once the OOP designer is started, its log is available in the Visual Studio Output window:
The default verbosity is set to Warnings, which includes Warnings and Errors (prior to VS 2022 17.2 was None, i.e. logging disabled). You can change the logging level to terser or more verbose under Tools -> Options -> Windows Forms Designer -> General -> Logging Level, e.g.:
When the OOP designer starts it launches the designer server process (aka DesignToolsServer.exe). If the server process fails to launch or connect to the Visual Studio, you may see the following error:
[02:59:20.7198643] [MyProj]: Timed out waiting for the design tools server process launch to complete.
[02:59:20.7668637] Microsoft.DotNet.DesignTools.Client.ServerException: Timed out waiting for the design tools server process launch to complete.
The default connection timeout is set to 2 minutes (prior to VS 2022 17.1p5 was 10 seconds). VS 2022 17.2 introduces the ability to increase the connection timeout, if necessary. You can change it under Tools -> Options -> Windows Forms Designer -> General -> Connection timeout, e.g.:
There can be various reasons why the server process may be taking longer than the allocated time. For example, some users have reported to have solutions with a large number of projects. The designer performs a shadow copying of the necessary files and folders before it can render your form or control, and if you have a slow hard drive, or the project files are located on a network drive, it can have a significant effect on how fast files are copied to the shadow cache folder.
Some customers have reported that the connection timeouts were caused by configurations of their antivirus services. In such cases it is recommended to add exclusion rules for devevn.exe and DesignToolsServer.exe, and this can unblock these executables and can increase the I/O of the shadow cache. For example, to add an exception to the Windows Defender so that it is not slowed down by the system call hooks Defender uses to provide real-time protection can be done with the following PowerShell command:
Add-MpPreference -ExclusionProcess 'devenv.exe'
Add-MpPreference -ExclusionProcess 'DesignToolsServer.exe'The designer server process uses long paths and requires path normalizations, the behaviours that can be altered by Switch.System.IO.UseLegacyPathHandling appcontext switch. The default value of the switch is false, and if the value is set to true either in devenv.exe.config (which is located somewhere like C:\Program Files\Microsoft Visual Studio\2022\Common7\IDE) or in the registry it will prevent the designer from loading with Argument Exception: Illegal characters in path error.