Name

    ARB_shading_language_100

Name Strings

    GL_ARB_shading_language_100

Contact

    John Kessenich, 3Dlabs, Inc. (johnk 'at' 3dlabs.com)
    Barthold Lichtenbelt, 3Dlabs, Inc. (barthold 'at' 3dlabs.com)
    Jon Leech, SGI (ljp 'at' sgi.com)

IP Status

    Microsoft claims to own unspecified intellectual property related to
    programmable shading.

Status

    Complete. Approved by the ARB on June 11, 2003.
    Updated revision 8 approved by the ARB on June 17, 2004.

Version

    Last Modified Date: April 6, 2004
    Revision: 8

Number

    ARB Extension #33

Dependencies

    This extension is written against the OpenGL 1.5 Specification

    ARB_shader_objects, ARB_fragment_shader, and ARB_vertex_shader are
    required to utilize the OpenGL Shading Language associated with this
    extension.

Overview

    This extension string indicates that the OpenGL Shading Language is
    supported. The Shading Language is defined by a separate specification
    document which can be downloaded from

	http://www.opengl.org/documentation/oglsl.html

Issues

    1) How do we indicate revisions in the supported version of the Shading
       Language?

	RESOLVED: Add a SHADING_LANGUAGE_VERSION query. This query was not
	present in the initial version of the extension. Therefore,
	applications should be prepared to detect an INVALID_ENUM error
	being raised by glGetString(GL_SHADING_LANGUAGE_VERSION). If this
	error is raised, but ARB_shading_language_100 is defined in the
	EXTENSIONS string, the application can assume that the initial
	release of the Shading Language (1.00, which was numbered "1.051"
	corresponding to document revision 51) is supported.

    2) What is the format of the SHADING_LANGUAGE_VERSION string? How does
       it map onto the release number of the shading language specification?

	RESOLVED: Identical to the VERSION string format:
	"major.minor[.release] [vendor info]". The release number is an
	optional vendor release number, not the shading language
	specification document release number (which is never visible to
	apps).

	The "1.051" release number of the initial Shading Language
	specification document corresponds to a SHADING_LANGUAGE_VERSION
	string of "1.00", since "51" was the revision number of the
	document, not the minor number.

	Going forward, the specification and query must always use the same
	encoding for major and minor numbers. The second release of the
	specification will be labelled "version 1.10, document revision 55",
	and the corresponding SHADING_LANGUAGE_VERSION string will be "1.10"
	(we chose to bump the minor version directly to 10 to avoid problems
	with leading 0s, and confusion with the old "1.051" document release
	number).

	Document release and vendor release numbers need not have any
	relation to each other, since they represent changes other than
	functionality, such as bug fixes and optimizations (for the
	implementation), and typos and errata for the specification).

	Functional changes to the shading language must always be indicated
	by an increase in the specification minor version number. Such
	changes may or may not correspond to changes to the core OpenGL
	version number as well, depending on whether or not they are visible
	in the OpenGL API.

    3) Should SHADING_LANGUAGE_VERSION be added to the state tables?

	RESOLVED: Yes. The other GetString queries (VERSION, EXTENSIONS,
	RENDERER, and VENDOR), which have been omitted in the past, should
	also be added, along with a new type code for string state values.

    4) What should the exact wording of the "IP Status" language be?

	Microsoft has made claims towards the low-level vertex shader and
	towards the generic programming framework proposed but not accepted
	into OpenGL 1.4, although that framework did not specify an actual
	shading language. Additional verbal statements made by Dave Aronson
	suggest that Microsoft may feel its claims extend to all
	programmable shading implementations. In fairness to implementers,
	we need to note the possibility of such a claim while also noting
	our lack of any specific information about what IP is being claimed.

New Tokens

    Accepted by the <name> parameter of GetString:

	SHADING_LANGUAGE_VERSION_ARB		0x8B8C

Additions to Chapter 6 of the OpenGL 1.5 Specification (State and State
Requests)

    Modify Section 6.1.11, Pointer and String Queries

    ... returns a pointer to a static string describing some aspect of the
    current GL connection(1).
       {footnote 1: Applications making copies of these static strings
	should never use a fixed-length buffer, because the strings may grow
	unpredictably over time resulting in buffer overflow when copying.
	This is particularly true of the EXTENSIONS string, which has become
	extremely long in some GL implementations.}
    The possible values for <name> are VENDOR, RENDERER, VERSION,
    SHADING_LANGUAGE_VERSION, and EXTENSIONS. The format of the RENDERER and
    VENDOR strings is implementation dependent. The EXTENSIONS string
    contains a space separated list of extension names (the extension names
    themselves do not contain any spaces). The VERSION and
    SHADING_LANGUAGE_VERSION strings are laid out as follows:

	<version number><space><vendor-specific information>

    The version number is either of the form <major_number.minor_number> or
    <major_number.minor_number.release_number>, where the numbers all have
    one or more digits. The <release_number> and vendor specific information
    are optional. However, if present, then they pertain to the server and
    their format and contents are implementation dependent.


    Add to Table 6.3, State variable types

	Type code   Explanation
	---------   ----------------------
	    S	    NULL-terminated string

Errors

    The error INVALID_ENUM may be generated by GetString if <name> is
    SHADING_LANGUAGE_VERSION, but only the initial version of this extension
    is supported. In this case, the implementation will support the initial
    release (version 1.00, document version labelled "1.051") of the OpenGL
    Shading Language.

New Implementation Dependent State

    Added to table 6.30 (Implementation Dependent Values)

    Get Value		     Type  Get Command	Minimum Description	     Sec.    Attrib
						Value
    ---------		     ----  -----------	------- -----------	     ----    ------
    EXTENSIONS		     S	   GetString	   -	Supported extensions 6.1.11  -
    RENDERER		     S	   GetString	   -	Renderer string      6.1.11  -
    SHADING_LANGUAGE_VERSION S	   GetString	   -	Shading Language     6.1.11  -
	_ARB						version supported
    VENDOR		     S	   GetString	   -	Vendor string	     6.1.11  -
    VERSION		     S	   GetString	   -	OpenGL version	     6.1.11  -
							supported

Revision History

   Date: 2004/04/06
   Revision: 8
      - Corrected several typos and noted an additional reason for going to
	minor release number 10 instead of 1 (ambiguity relative to the
	initial "1.051" document release number).

   Date: 2004/04/06
   Revision: 7
      - Clarified that the release_number field is also vendor information,
	and that the major.minor notation of the query and the shading
	language specification must match in the future. Noted that not
	supporting the query implies that version 1.00 of the shading
	language is supported.

   Date: 2004/04/05
   Revision: 6
      - Fixed some typos. Changed errors section to require that the initial
	version of the shading language be supported if the
	SHADING_LANGUAGE_VERSION query fails, but the extension is
	supported.

   Date: 2004/04/02
   Revision: 5
      - Assigned enum value to SHADING_LANGUAGE_VERSION. Corrected
	SHADER_VERSION to SHADING_LANGUAGE_VERSION in one place previously
	missed.

   Date: 2004/03/26
   Revision: 4
      - Changed query from SHADER_VERSION to SHADING_LANGUAGE_VERSION to
	match extension name. Added an issue to determine exact wording of
	the IP Status comment.

   Date: 2004/03/19
   Revision: 3
      - Resolved issues 2 and 3. Required that future shading language
	specification version numbers match the SHADER_VERSION format.
	Corrected omission of other GetString queries from the state tables.

   Date: 2004/03/14
   Revision: 2
      - Corrected URL to refer to opengl.org instead of 3dlabs.com.
      - Added SHADER_VERSION string query. Defined format of the shader
	version string and described fallback behavior for older
	implementations of the extension.
