Wayland is a display server protocol that aims to eventually replace the aging X Window System (X11) as the primary display technology on Linux and Unix-like operating systems. Development on Wayland started in 2008 by Kristian Høgsberg and other developers who were dissatisfied with the technical limitations and outdated architecture of X11, which originated in the 1980s. Wayland implements a client-server model where the display server (compositor) takes direct control of the graphics hardware while individual clients communicate with the server to display application surfaces and receive user input events.
Some key architectural differences between X11 and Wayland include:
- X11 uses a network-transparent protocol based on exchanging messages over sockets. Wayland compositors and clients use shared memory buffers for faster communication without networking overhead.
- The X11 server maintains a single global root graphics window that all applications draw to. Wayland compositors render surfaces from clients directly to outputs without a global root window.
- X11 clients can listen to each other's inputs, allowing for keylogging. Wayland enforces isolation between clients for improved security.
- X11 uses core protocols like XRandR for resolution setting and XRender for image transfer. Wayland uses standard APIs like EGL, OpenGL ES, and Vulkan for all rendering.
- X11 shares a single OpenGL context globally. Wayland allows clients to create their own scoped contexts, avoiding conflicts.
Some of the major goals and potential benefits of Wayland include:
- Enhanced security - Client isolation prevents malicious apps from spying on other apps. The Wayland compositor runs with minimal privileges since clients cannot access input or graphics hardware directly.
- More modern architecture - Removing legacy X11 components like the root window simplifies the display stack and improves performance.
- Multi-monitor support - Wayland natively handles varying resolutions and pixel densities across displays. X11 struggles with mixed-DPI setups.
- Improved graphics - Direct rendering routed through the compositor avoids X11’s overhead, increasing frame rates. vsync and buffered rendering reduce stuttering.
- Portability - Wayland is not as tightly coupled to Unix or X, enabling reuse across Linux, Android, Chrome OS, and more.
- Power efficiency - The compositor handles monitor low power states seamlessly unlike X11 which relies on driver-specific handling.
- Forward-looking protocol - Designed for modern use cases like high-density screens, touch input, and composited graphics.
Some current adoption challenges include:
- Application compatibility - Existing X11 apps need ports to native Wayland APIs for ideal functionality under Wayland compositors.
- Screen sharing - The isolation between clients breaks X11-based screen sharing that depended on remote access. New protocols are in development.
- Graphics tablets - Pressure and tilt support was initially lacking but is improving in toolkits and drivers.
- Proprietary GPU drivers - Vendors like NVIDIA depend heavily on X11 APIs, causing degraded Wayland performance.
While X11 remains the default on most Linux desktops for compatibility, Wayland adoption is increasing driven by demand for improved user experience. Newer applications and toolkits implement Wayland natively. Android, Tizen, and ChromeOS rely on Wayland-based compositors exclusively.
The X11 to Wayland transition will continue gradually as more functionality gets ported. But Wayland’s cleaner and more performant architecture make it a worthwhile successor for Linux graphics. Despite adoption challenges, Wayland represents the future for the Linux display stack as X11 shows its age.