qb64/internal/help/_gliewport.md

_glViewport: set the viewport

Syntax

;QB64:SUB _glViewport (BYVAL x AS LONG, BYVAL y AS LONG, BYVAL width AS LONG, BYVAL height AS LONG) ;C/C++:void _glViewport(GLint x, GLint y, GLsizei width, GLsizei height);

; x, y

Specify 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.

Description

_glViewport specifies the affine transformation of x and y from normalized device coordinates to window coordinates. Let (x_nd, y_nd) be normalized device coordinates. Then the window coordinates (x_w, y_w) are computed as follows:

glapi viewport equations

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.

Error(s)

_GL_INVALID_VALUE is generated if either width or height is negative.

Use With

_glGet with argument _GL_VIEWPORT

_glGet with argument _GL_MAX_VIEWPORT_DIMS

See Also

_GL _glDepthRange, _glViewportArray, _glViewportIndexed