xref: /third_party/openGLES/extensions/SGIX/GLX_SGIX_fbconfig_float.txt

XXXmdf - incomplete

Name

    SGIX_fbconfig_float

Name Strings

    GLX_SGIX_fbconfig_float

Version
    
    $Date: 1999/01/08 19:41:53 $ $Revision: 1.1 $

Number

    XXXmdf

Dependencies

    SGIX_fbconfig is required

Overview

    This extension enhances the fbconfig visual selection and description
    capabilities by adding support for floating-point attributes. While
    SGIX_fbconfig only provides for integral attributes, some visual
    attributes are best described with floating point
    numbers.  Applications which seek to choose visuals based on those
    attributes may use the facilites described in this extension.

Issues

    * There is an implicit assumption that all attribute tokens can be
      cast to double and back to int without losing information.  There
      are currently no tokens with more than 16 significant bits so this
      is almost certainly a safe assumption, however it should be noted
      as a limitation.

New Procedures and Functions

    int glXGetFBConfigFltAttribSGIX(Display *dpy, 
			            GLXFBConfigSGIX config,
			            int attribute,
			            double *value);

    GLXFBConfigSGIX *glXChooseFBConfigWithFltSGIX(
		Display *dpy,
		int screen,
		const int *int_attrib_list,
		const double *flt_attrib_list,
		int *nelements);

New Tokens

    None

Additions to the OpenGL 1.0 Specification

    None

Additions to the GLX Specification

    [Added following the description of glXChooseFBConfigSGIX]

    Use glXChooseFBConfigWithFltSGIX in place of
    glXChooseFBConfigSGIX in order to select GLXFBConfigSGIXs based on
    floating point attributes.

        GLXFBConfigSGIX *glXChooseFBConfigWithFltSGIX(
		Display *dpy,
		int screen,
		const int *attrib_list,
		const double *flt_attrib_list,
		int *nelements);

    If <flt_attrib_list> is NULL then glXChooseFBConfigWithFltSGIX behaves
    identically to glXChooseFBConfigSGIX; otherwise, the attributes
    listed in <flt_attrib_list> are used in conjunction with
    the attributes listed in <attrib_list> to select a
    matching GLXFBConfigSGIX.
    
    All attributes have an inherent data type, listed in Table 3, such as
    integer, boolean, enumerated, bitmask, XID, or floating point.
    Any of these attributes may appear in <attrib_list>, although
    in the case of floating point attributes the cast to integer may lose
    information. Only floating point attributes may appear in
    <flt_attrib_list>.  Since the attribute tokens are integer constants,
    they must be cast to double to appear in <flt_attrib_list>.  Any
    attribute which appears in both lists will take on the value from
    <flt_attrib_list>.

    [Added following the description of glXGetFBConfigAttribSGIX]

    To get the value of a floating point GLX attribute for a
    GLXFBConfigSGIX use:

        int glXGetFBConfigFltAttribSGIX(Display *dpy, 
			                GLXFBConfigSGIX config,
			                int attribute,
			                double *value);

    glXGetFBConfigFltAttribSGIX has the same semantics as 
    glXGetFBConfigAttribSGIX, although it returns a double value
    rather than an int value.  Non-floating-point attributes undergo
    a cast to double before they are returned.


GLX Protocol

    None

Errors

    None

New State

    None

New Implementation Dependent State

    None