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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