glViewport — set the viewport
void glViewport( | GLint | x, |
| GLint | y, | |
| GLsizei | width, | |
| GLsizei | height); |
x, ySpecify the lower left corner of the viewport rectangle, in pixels. The initial value is (0,0).
width, height
Specify 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.
glViewport specifies the affine transformation of
and
from
normalized device coordinates to window coordinates.
Let
be normalized device coordinates.
Then the window coordinates
are computed as follows:
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.
GL_INVALID_VALUE is generated if either width or height is negative.
GL_INVALID_OPERATION is generated if glViewport
is executed between the execution of glBegin
and the corresponding execution of glEnd.
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