# glViewport

The glViewport function sets the viewport.

```void glViewport(
GLint x,
GLint y,
GLsizei width,
GLsizei height
);
```

#### Parameters

x, y
The lower-left corner of the viewport rectangle, in pixels. The default is (0,0).
width, height
The width and height, respectively, of the viewport. When an OpenGL context is first attached to a window, width and height are set to the dimensions of that window.

#### Remarks

The glViewport function specifies the affine transformation of x and y from normalized device coordinates to window coordinates. Let (xnd, ynd) be normalized device coordinates. The window coordinates (xw, yw) are then computed as follows:

Viewport width and height are silently clamped to a range that depends on the implementation. This range is queried by calling glGet with argument GL_MAX_VIEWPORT_DIMS.

The following functions retrieve information related to glViewport:

glGet with argument GL_VIEWPORT

glGet with argument GL_MAX_VIEWPORT_DIMS

#### Error Codes

The following are the error codes generated and their conditions.

Error code Condition
GL_INVALID_VALUE Either width or height was negative.
GL_INVALID_OPERATION glViewport was called between a call to glBegin and the corresponding call to glEnd.

#### Requirements

Windows NT/2000: Requires Windows NT 3.5 or later.
Windows 95/98: Requires Windows 95 or later. Available as a redistributable for Windows 95.