# GLAPI/glViewportIndexed

Core in version 4.4 4.1 ARB_viewport_array

glViewportIndexed: set a specified viewport

## Function Definition

 void glViewportIndexedf(GLuint index​, GLfloat x​, GLfloat y​, GLfloat w​, GLfloat h​);
void glViewportIndexedfv(GLuint index​, const GLfloat *v​);

index
Specify the first viewport to set.
x, y
For glViewportIndexedf, specifies the lower left corner of the viewport rectangle, in pixels. The initial value is (0,0).
width, height
For glViewportIndexedf, specifies the width and height of the viewport. When a GL context is first attached to a window, width​ and height​ are set to the dimensions of that window.
v
For glViewportIndexedfv, specifies the address of an array containing the viewport parameters.

## Description

glViewportIndexedf and glViewportIndexedfv specify the parameters for a single viewport. index​ specifies the index of the viewport to modify. index​ must be less than the value of GL_MAX_VIEWPORTS​. For glViewportIndexedf, x​, y​, w​, and h​ specify the left, bottom, width and height of the viewport in pixels, respectively. For glViewportIndexedfv, v​ contains the address of an array of floating point values specifying the left (x), bottom (y), width (w), and height (h) of each viewport, in that order. x and y give the location of the viewport's lower left corner, and w and h give the width and height of the viewport, respectively. The viewport specifies the affine transformation of x and y from normalized device coordinates to window coordinates. Let (xnd, ynd) be normalized device coordinates. Then the window coordinates (xw, yw) are computed as follows:

$x_w = (x_{nd} + 1)\left ( \tfrac{width}{2} \right) + x$

$y_w = (y_{nd} + 1)\left ( \tfrac{height}{2} \right) + y$

The location of the viewport's bottom left corner, given by (x, y) is clamped to be within the implementaiton-dependent viewport bounds range. The viewport bounds range [min, max] can be determined by calling glGet with argument GL_VIEWPORT_BOUNDS_RANGE​. Viewport width and height are silently clamped to a range that depends on the implementation. To query this range, call glGet with argument GL_MAX_VIEWPORT_DIMS​.

The precision with which the GL interprets the floating point viewport bounds is implementation-dependent and may be determined by querying the impementation-defined constant GL_VIEWPORT_SUBPIXEL_BITS​.

Calling glViewportIndexedfv is equivalent to calling with first​ set to index​, count​ set to 1 and v​ passsed directly. glViewportIndexedf is equivalent to:

    void glViewportIndexedf(GLuint index, GLfloat x, GLfloat y, GLfloat w, GLfloat h)
{
const float v[4]  = { x, y, w, h };
glViewportArrayv(index, 1, v);
}


== Errors ==

GL_INVALID_VALUE​ is generated if index​ is greater than or equal to the value of GL_MAX_VIEWPORTS​.

GL_INVALID_VALUE​ is generated if either width​ or height​ is negative.

## Associated Gets

with argument GL_VIEWPORT​

with argument GL_MAX_VIEWPORT_DIMS​

with argument GL_VIEWPORT_BOUNDS_RANGE​

with argument GL_VIEWPORT_SUBPIXEL_BITS​