WGL

WGL, or Windows Graphics Library, is the OpenGL interface for the Windows operating system. It provides the set of functions that allow applications to create and manage OpenGL rendering contexts, select pixel formats, and load OpenGL extensions on Windows. WGL is part of the Windows platform SDK and serves as the Windows-specific counterpart to GLX on Unix-like systems.

Core concepts in WGL include the device context (HDC) and the rendering context (HGLRC). An application obtains an HDC for a window, chooses a suitable pixel format, creates an OpenGL rendering context with wglCreateContext, and makes it current with wglMakeCurrent. Rendering then occurs through OpenGL. For modern OpenGL, developers often create a context with specific version and profile attributes using wglCreateContextAttribsARB, a function obtained via the WGL extension mechanism.

Extensions and extension loading are central to WGL. Extensions add functionality such as enhanced pixel format selection and advanced context creation. Extension entry points are retrieved at runtime using wglGetProcAddress. A common pattern is to create a temporary context to obtain addresses for extension functions, then create a final context with the desired attributes.

History and scope: WGL evolved with OpenGL and Windows drivers to support newer graphics features and contexts. It remains Windows-only, with cross-platform development typically using GLX on X11 or EGL for embedded/desktop environments. Developers must manage the lifecycle of HDCs and HGLRCs and account for variations in extension availability across driver versions and Windows updates.

See also: OpenGL, GLX, EGL, Windows API, HDC, HGLRC, wglCreateContext, wglMakeCurrent, wglGetProcAddress.