GlViewport: Difference between revisions

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{{DISPLAYTITLE:_glViewport}}
{{DISPLAYTITLE:_glViewport}}
'''_glViewport:''' set the viewport
The '''_glViewport''' statement sets the viewport.




{{PageSyntax}}
{{PageSyntax}}
: [[_glViewport]] GLint {{Parameter|x}}, GLint {{Parameter|y}}, GLsizei {{Parameter|width}}, GLsizei {{Parameter|height}}


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


 
{{PageParameters}}
; x, y
* OpenGL is using its own set of variable types to describe its command parameters.
: Specify the lower left corner of the viewport rectangle, in pixels. The initial value is (0,0).
* Use the following table to find the respective QB64 [[Variable Types]].
; width, height
{{OpenGLTypesPlugin}}
: Specify the width and height of the viewport. When a GL context is first attached to a window, {{Parameter|width}} and {{Parameter|height}} are set to the dimensions of that window.




{{PageDescription}}
{{PageDescription}}
 
* OpenGL's documentation is available in several places, so we won't reproduce it here for another time.
'''_glViewport''' specifies the affine transformation of ''x'' and ''y'' from normalized device coordinates to window coordinates. Let (x<sub>nd</sub>, y<sub>nd</sub>) be normalized device coordinates. Then the window coordinates (x<sub>w</sub>, y<sub>w</sub>) are computed as follows:
* The full description for this command can be found at [https://learn.microsoft.com/en-us/windows/win32/opengl/glviewport Microsoft Docs] and is also valid for QB64 usage.
 
{{glapi viewport equations}}
 
Viewport width and height are silently clamped to a range that depends on the implementation. To query this range, call {{KW|_glGet}} with argument {{KW|_GL_MAX_VIEWPORT_DIMS}}.
 
 
{{PageErrors}}
 
{{KW|_GL_INVALID_VALUE}} is generated if either {{Parameter|width}} or {{Parameter|height}} is negative.
 
 
{{PageUseWith}}
 
{{KW|_glGet}} with argument {{KW|_GL_VIEWPORT}}
 
{{KW|_glGet}} with argument {{KW|_GL_MAX_VIEWPORT_DIMS}}




{{PageSeeAlso}}
{{PageSeeAlso}}
 
* [[_GL|SUB _GL]]
[[_GL|SUB _GL]]
* [[_glBegin]], [[_glDepthRange]]
{{KW|_glDepthRange}}, {{KW|_glViewportArray}}, {{KW|_glViewportIndexed}}
 
 
{{PageCopyright}}




{{PageNavigation}}
{{PageNavigation}}

Latest revision as of 01:57, 28 January 2023

The _glViewport statement sets the viewport.


Syntax

_glViewport GLint x, GLint y, GLsizei width, GLsizei height


Parameters

  • OpenGL is using its own set of variable types to describe its command parameters.
  • Use the following table to find the respective QB64 Variable Types.
   Table 2: Relations between the OpenGL variable types vs. C/C++ and QB64.
 ┌──────────────┬────────────────┬──────────────────────────────────────────┐
 │    OpenGL    │     C/C++      │     QB64                                 │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLenum       │ unsigned int   │ _UNSIGNED LONG                           │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLboolean    │ unsigned char  │ _UNSIGNED _BYTE                          │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLbitfield   │ unsigned int   │ _UNSIGNED LONG                           │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLbyte       │ signed char    │ _BYTE                                    │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLshort      │ short          │ INTEGER                                  │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLint        │ int            │ LONG                                     │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLsizei      │ int            │ LONG                                     │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLubyte      │ unsigned char  │ _UNSIGNED _BYTE                          │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLushort     │ unsigned short │ _UNSIGNED INTEGER                        │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLuint       │ unsigned int   │ _UNSIGNED LONG                           │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLfloat      │ float          │ SINGLE                                   │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLclampf     │ float          │ SINGLE                                   │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLdouble     │ double         │ DOUBLE                                   │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLclampd     │ double         │ DOUBLE                                   │
 ├──────────────┼────────────────┼──────────────────────────────────────────┤
 │ GLvoid   (1) │ void           │ _OFFSET(any fixed lenght string or _BYTE │
 │              │                │         array element)                   │
 └──────────────┴────────────────┴──────────────────────────────────────────┘
 Note: If a parameter has an asterisk (*) in front, then it's a pointer to
       the designated OpenGL variable type, rather than a value of that type.
       Those must be passed using the _OFFSET(...) notation.

 E.g.  GLuint *anyParam is actually the offset of a _UNSIGNED LONG (~&)
       variable or array, which must be passed as _OFFSET(anyVar~&) or
       _OFFSET(anyArr~&()) respectively.

  (1)  This type is regularly only used for pointers (with asterisk (*)) to
       any byte sized memory data, hence _BYTE or fixed length strings.


Description

  • OpenGL's documentation is available in several places, so we won't reproduce it here for another time.
  • The full description for this command can be found at Microsoft Docs and is also valid for QB64 usage.


See also


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