- set the viewport
C SPECIFICATION
PARAMETERS
_param1, _param2 Specify the lower left corner of the
viewport rectangle, in pixels. The ini-
tial value is (0,0).
_param3, _param4 Specify the width and height of the view-
port. When a GL context is first
attached to a window, _param3 and _param4
are set to the dimensions of that window.
DESCRIPTION
glViewport 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:
xw=(xnd+1)(_e_q_n_p_a_r_a_m__)+_eqnparam1
yw=(ynd+1)(_e_q_n_p_a_r_a_m__)+_eqnparam2
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.
ERRORS
GL_INVALID_VALUE is generated if either _param3 or _param4
is negative.
GL_INVALID_OPERATION is generated if glViewport is exe-
cuted between the execution of glBegin and the correspond-
ing execution of glEnd.
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