The latest Steam (beta) update adds support for screens with high pixel density when used on a Windows 10 client in combo with the Fall Creators Update. Next to the addition for high-DPI monitor support the new Steam client should also use less CPU when drawing the main window.
You can find instructions here to register for the beta. The full release notes are listed below:
Windows
- Added high-DPI monitor support when running under Windows 10 with the 2017 Creators Update
- Added window transition animations when opening, closing, or minimizing Steam windows
- Improved taskbar handling of Steam windows on multi-monitor systems
macOS
- Added support for turning off or restarting the system from Big Picture mode
- Improved native OS integration of Steam client windows. For example, Steam windows can now be dragged up past the menu bar to trigger the Spaces UI.
- Improved reliability of the Steam Input and Streaming Audio drivers for macOS
Linux
- Added a 2X-scaling mode with high-res text and graphics when running the Steam client in desktop mode on 4k-resolution monitors. You can also force 2X scaling with the "GDK_SCALE=2" environment variable, or disable it with "GDK_SCALE=1".
- Improved window-resizing interactions with the window manager
- Fixed an issue where the Steam client could prevent some desktop sessions from shutting down
General
- Reduced CPU usage of Steam when redrawing the UI, such as when the mouse is moved back and forth over part of the Library view
- Improved behavior when re-installing from retail discs or backup files, preferring to avoid downloads whenever possible
- Fixed an issue where corrupt workshop items could be re-downloaded endlessly
- Fixed an issue where the in-game overlay could crash or become unresponsive in some Vulkan-based games
Steam Input
- Added "Exit Application" controller action. When this action is used within a game, it will prompt the user if they actually want to quit and if confirmed will immediately close the application.
- Fixed some issues that could cause Steam Controller pairing to fail unexpectedly
- Improved support for typing accented characters with the on-screen keyboard on Mac systems
