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Name
MESA_window_pos
Name Strings
GL_MESA_window_pos
Contact
Brian Paul, brianp 'at' mesa3d.org
Status
Shipping (since Mesa version 1.2.8)
Version
$Id: MESA_window_pos.spec,v 1.1 1999/07/20 00:30:41 brianp Exp $
Number
XXX non assigned
Dependencies
OpenGL 1.0 is required.
The extension is written against the OpenGL 1.2 Specification
Overview
In order to set the current raster position to a specific window
coordinate with the RasterPos command, the modelview matrix, projection
matrix and viewport must be set very carefully. Furthermore, if the
desired window coordinate is outside of the window's bounds one must
rely a subtle side-effect of the Bitmap command in order to circumvent
frustum clipping.
This extension provides a set of functions to directly set the
current raster position, bypassing the modelview matrix, the
projection matrix and the viewport to window mapping. Furthermore,
clip testing is not performed.
This greatly simplifies the process of setting the current raster
position to a specific window coordinate prior to calling DrawPixels,
CopyPixels or Bitmap.
New Procedures and Functions
void WindowPos2dMESA(double x, double y)
void WindowPos2fMESA(float x, float y)
void WindowPos2iMESA(int x, int y)
void WindowPos2sMESA(short x, short y)
New Tokens
none
Additions to Chapter 2 of the OpenGL 1.2 Specification (OpenGL Operation)
- (2.12, p. 41) Insert after third paragraph:
Alternately, the current raster position may be set by one of the
WindowPosMESA commands:
void WindowPos{234}{sidf}MESA( T coords );
void Window Pos{234}{sidf}vMESA( T coords );
WindosPos4MESA takes four values indicating x, y, z, and w.
WindowPos3MESA (or WindowPos2MESA) is analaguos, but sets only
x, y, and z with w implicitly set to 1 (or only x and y with z
implicititly set to 0 and w implicitly set to 1).
WindowPosMESA operates like RasterPos except that the current modelview
matrix, projection matrix and viewport parameters are ignored and the
clip test operation always passes. The current raster position values
are directly set to the parameters passed to WindowPosMESA. The current
color, color index and texture coordinate update the current raster
position's associated data.
The current raster distance ??? XXX ???
Additions to the AGL/GLX/WGL Specifications
None
GLX Protocol
Not specified at this time. However, a protocol message very similar
to that of RasterPos is expected.
Errors
INVALID_OPERATION is generated if WindowPosMESA is called betweeen
Begin and End.
New State
None.
New Implementation Dependent State
None.
Revision History
* Revision 1.0 - Initial specification
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