glViewportGLint

glViewportGLint is the name sometimes used to refer to the OpenGL viewport function’s parameter type specification, namely the signature glViewport(GLint x, GLint y, GLint width, GLint height). In this context, GLint is the signed integer type defined by the OpenGL API for 32‑bit values, typically mapped to the C language type int. The function defines the affine mapping from Normalized Device Coordinates (NDC) to window coordinates, which is performed after clipping but before the final rasterization stage. The first two parameters, x and y, specify the lower left corner of the viewport rectangle in pixel coordinates relative to the current window. The width and height specify the size of the viewport in pixels.

When a rendering surface is created, OpenGL implicitly assigns a default viewport that covers the entire drawing buffer. Applications change this setting when rendering to sub‑regions of a window, implementing split screens, or performing multi‑view rendering. A viewport transformation also interacts with the scissor test; the scissor rectangle must lie within the viewport for fragments to be discarded.

The values passed to glViewportGLint must follow several constraints: width and height must be non‑negative; if either is zero the viewport is empty and no fragments are generated. Excessively large values may clip coordinates to the clip space. Many contemporary graphics APIs re‑use the signature of glViewport for compute shaders, transform feedback, and frame‑buffer operations, using the same GLint type.

For those working in a C or C++ environment, a typical call looks like: glViewport(0, 0, width, height); where width and height are integers derived from the window size or render target. In modern OpenGL, the function remains unchanged, and developers often refer to it simply as glViewport or glViewportGLint in documentation to emphasize the GLint parameter types.