extensions/SGI/GLX_SGI_transparent_pixel.txt

XXX - Not complete yet!!!

Name

    SGI_transparent_pixel

Name Strings

    GLX_SGI_transparent_pixel

Version

    $Date: 1998/04/21 03:53:16 $ $Revision: 1.3 $

Number

    153

Dependencies

    None

Overview

    This extension provides a means to request a visual with a
    transparent pixel and to query whether a visual supports a
    transparent pixel value as well as the value of the transparent
    pixel.  Note that the notion of level and transparent pixels
    are orthogonal as bother layer 1 and layer 0 visuals may or
    may not have a transparent pixel value.

Issues

    Is it okay to return a vector in glXGetConfig ?

    Should the RGB color value use something more X-like, e.g.
    16-bit component values.

    I think its a good idea to use integer RGBA color components
    so that one can use some argument about exact integer values
    being rasterized predictable but we all know the transparent
    pixel value is going to be (1.0,1.0,1.0) or (0.0,0.0,0.0) so
    maybe we should provide a simpler hack?

    Is there problem with the value queries returning zero if the
    visual doesn't contain a transparent pixel?

    Why not admit that zero is the one true transparent
    pixel value and simply live with GLX_TRANSPARENT_PIXEL
    as the only new enum?

New Procedures and Functions

    None

New Tokens

    GLX_TRANSPARENT_PIXEL_SGI
    GLX_TRANSPARENT_COLOR
    GLX_TRANSPARENT_INDEX


Additions to Chapter 2 of the 1.0 Specification (OpenGL Operation)

    None

Additions to Chapter 3 of the 1.0 Specification (Rasterization)

    None

Additions to Chapter 4 of the 1.0 Specification (Per-Fragment Operations and
the Framebuffer)

    None

Additions to Chapter 5 of the 1.0 Specification (Special Functions)

    None

Additions to Chapter 6 of the 1.0 Specification (State and State Requests)

    None

Additions to the GLX Specification
	
    [Add to Section 3.2.2 of the 1.0 GLX Specification (Configuration
     Management)]

    [Add to Table 1: Configuration Attributes]

    GLX_TRANSPARENT_PIXEL_SGI    boolean    True if contains a transparent pixel
    GLX_TRANSPARENT_INDEX_SGI    integer    if RGB mode or no transparent pixel
					    0, else transparent index value
    GLX_TRANSPARENT_COLOR_SGI	 Color*4    if index mode or no transparent
					    pixel 0, else scaled component
					    values
    
    type Color is essentially the OpenGL signed integer color type which
    maps to an OpenGL float color in the range (0.0,1.0) as described
    in table 2.4 of the 1.0 OpenGL specification.


Errors

    No new errors for glXGetConfig or glXChooseVisual.

New State

    None

New Implementation Dependent State

    None