Run the game and encounter no more freezes III. From this similar question, make sure GPU scaling is disabled and your refresh rate is set correctly in your GPU control panel. Cancel it, exit steam and copy the already installed Portal 2 folder from your backup to the new one.I don't think those were ever fixed, so your only option may be to uninstall those and use the default Windows drivers.
Several version of NVidia drivers have been known to break it, so make sure to update your drivers.I believe this has been fixed in the latest version of Windows. Many gamers do this intentionally because exclusive fullscreen has better performance. Right click on the Connect Using DNS Name option and choose the Properties command from the shortcut menu. One common cause of the Horizon black screen problem is that a firewall is blocking the client from accessing a required network port. If you disabled Fullscreen Optimization for the game or disabled it system-wide, the slow alt+tab behavior will return. Next, expand the VMware Horizon Agent Configuration container and select the Agent Configuration option.This feature is always on by default, but a number of things can cause it to stop working. However, beginning with Windows 10 v1803 (March 2018), Microsoft introduced a feature called "Fullscreen Optimizations" that forces all games to use Borderless Windowed mode, even when the game requests exclusive fullscreen. This used to be normal for exclusive fullscreen games.