extensions/SGIX/GLX_SGIX_color_typeXXX.txt

XXX - Not complete yet!!!
XXX - Apparently superseded by color_type.spec?

Name

    SGIX_color_typeXXX

Name Strings

    GLX_SGIX_color_typeXXX

Version
    
    $Date: 1999/04/03 08:40:47 $ $Revision: 1.2 $

Number

    72

Dependencies

    SGIX_FBConfig is required
    SGIX_pbuffer is required

Overview

    This extension enhances the fbconfig types to support signed
    and complex data types.  These data types are useful to
    imaging applications that often require signed data or
    complex data formats.

Issues

   * at some point in the future, we may also need to add an internal
     format attribute.  For Redtail, we currently can not interleave
     complex components; the plan is to have them "striped". 

   * we may also want to add GLX_FLOAT_COMPONENTS_SGIX at some point.

   * with this current scheme, there's currently no way of extracting
     individual (i.e. real vs. complex) components.  Can we just add
     another attribute that will allow us to do this?
     (We are currently implying that both real and complex values have
     the same bit depth/type which seems to be the current norm....
     for full flexibility we might want to consider setting the
     individual real and complex bit depth;  but, I currently can't
     see the usefulness of having this supported).


New Procedures and Functions

    None


New Tokens

    Accepted by the <attributes> parameter of glXGetFBConfigAttribSGIX, and 
    by the <attrib_list> parameter of glXChooseFBConfigSGIX:

        GLX_COLOR_TYPE_SGIX		0x????

    Returned by glXGetFBConfigAttribSGIX (when <attribute> is set to 
    GLX_COLOR_TYPE_SGIX) and accepted by the <attrib_list> parameter of 
    glXChooseFBConfigSGIX (following the GLX_COLOR_TYPE_SGIX token):

        GLX_UNSIGNED_COMPONENTS_SGIX		0x00000001
        GLX_SIGNED_COMPONENTS_SGIX		0x00000002
        GLX_COMPLEX_COMPONENTS_SGIX		0x00000003


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 Frame buffer)

    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

    [Added to the description of glXChooseFBConfigSGIX ]

   If GLX_COLOR_TYPE_SGIX is in <attrib_list> then the value that follows
    indicates how color values are represented in the framebuffer:

	GLX_UNSIGNED_COMPONENTS_SGIX specifies that each color component
	is stored as an unsigned value.

	GLX_SIGNED_COMPONENTS_SGIX specifies that each color component
	is stored as a signed value.  Typically this means that
	one bit per component is used to encode the sign of the
	value, with a resulting loss in the range of values which
	can be stored in the framebuffer.  The actual representation
	of the data (two's complement, sign magnitude, floating point,
	etc) is unspecified.

	GLX_COMPLEX_COMPONENTS_SGIX specifies that each color component
	is stored as a complex number.  The distribution of bits
	used to represent the real and imaginary portions of the
	complex number are unspecified as is the actual representation
	of the data (two's complement, sign magnitude, floating point etc).
    
    In general, only non-displayable drawable types (e.g. GLXPbuffers) will
    be able to be created with FBConfigs which support signed or complex color
    component types (see GLX_DRAWABLE_TYPE_SGIX).


Errors

    [ Do we need a new error to indicate if a system doesn't
      support signed and/or complex buffers? ]
 
New State

    None

New Implementation Dependent State

    None