glxheads

glxheads [display_name...]

display_name
    Specifies an X display to connect to and render on. This can be a display number like :0, a screen number like :0.1, or a full display specification like localhost:0 or remotehost:0. If no display_name is provided, glxheads defaults to the display specified by the DISPLAY environment variable (e.g., :0).

glxheads is a lightweight diagnostic utility from the Mesa 3D Graphics Library project, designed to verify basic OpenGL (GLX) rendering functionality across multiple X Window System displays or screens simultaneously. When invoked, it attempts to open an OpenGL rendering window on each specified X display, rendering a simple 3D animation (often a spinning gear or triangle). This tool is particularly useful for debugging multi-monitor setups, verifying GLX acceleration on remote X displays, or confirming that OpenGL contexts can be successfully created and rendered on different display outputs. It provides immediate visual feedback and outputs basic GLX version and renderer information for each display, aiding in the diagnosis of graphics driver and display configuration issues in complex environments.

glxheads is a very basic test; it doesn't stress the GPU extensively or test advanced OpenGL features. It primarily verifies GLX context creation and basic rendering. While useful for initial setup validation, it's not a comprehensive benchmark. It requires an X server with GLX support.

The primary purpose of glxheads is to test and confirm basic GLX (OpenGL Extension to the X Window System) functionality and multi-head display configurations. It ensures that OpenGL contexts can be successfully created and rendered across multiple X screens or displays simultaneously, providing visual confirmation and diagnostic output for each.

For each display it connects to, glxheads typically outputs diagnostic information including the GLX version, OpenGL vendor string, renderer string, and OpenGL version string. This information is crucial for verifying the active OpenGL driver and its capabilities on each specific display.

glxheads is part of the mesa-demos (or mesa-utils on some distributions) package, which bundles various OpenGL demonstration and testing programs. It has been a long-standing utility in the Linux graphics ecosystem, providing a fundamental tool for developers and users to quickly ascertain GLX and multi-display functionality within the X Window System. Its core purpose and usage have remained consistent over time, serving as a reliable first-line diagnostic for OpenGL display issues.

glxgears(1), xdpyinfo(1), xrandr(1), mesa-utils(7)