Name EXT_libglvnd Name Strings GLX_EXT_libglvnd Contact Kyle Brenneman, NVIDIA, kbrenneman at nvidia.com Contributors Kyle Brenneman Adam Jackson Andy Ritger Robert Morell Arthur Huillet Martin Peres Status Complete Version Last Modified Date: March 8, 2016 Revision: 1 Number OpenGL Extension #482 Dependencies GLX version 1.3 is required. This specification is written against the wording of the GLX 1.4 Specification. Overview This extension allows the vendor-neutral GLX client library, libglvnd, to determine which vendor-specific driver is needed to support a given GLX drawable or X11 screen. This GLX extension is not intended to be used directly by applications. Instead, it is intended to be used by the GLX client library. IP Status No known IP claims. New Procedures and Functions None New Types None New Tokens Accepted by the parameter of glXQueryServerString: GLX_VENDOR_NAMES_EXT 0x20F6 Additions to Chapter 3 of the GLX 1.4 Specification (Functions and Errors) [Modify Section 3.3.2, GLX Versioning] [Replace the 2nd sentence of the 5th paragraph with the following] "The possible values for and the format of the strings is the same as for glXGetClientString. may also be GLX_VENDOR_NAMES_EXT." [Add the following paragraph to the end of the section] "If is GLX_VENDOR_NAMES_EXT, then the returned string is a space-separated sequence of vendor names. The names are in order of preference, with the most preferred vendor first." [Modify Section 3.3.6, Querying Attributes] [Replace the 2nd sentence of the 1st paragraph with the following] " must be set to one of GLX_WIDTH, GLX_HEIGHT, GLX_PRESERVED_CONTENTS, GLX_LARGEST_PBUFFER, GLX_FBCONFIG_ID, or GLX_SCREEN" [Add the following paragraph just before the last of the section] "If is GLX_SCREEN, then will be the screen number that the drawable was created on." GLX Protocol This extension does not add any new requests. The GLX_VENDOR_NAMES_EXT enum is used with the existing glXQueryServerString request, and GLX_SCREEN is added to the attributes in the glXGetDrawableAttributes reply. Errors None Issues 1) Should GLX_VENDOR_NAMES_EXT contain a single vendor name or a list of names? RESOLVED: Allow a list of names. Allowing multiple names would allow for multiple client-side vendor libraries that work with a single server-side driver. With only a single name, selecting between multiple client drivers would require some form of additional configuration. For example, some vendors may have both a proprietary client-side vendor library and an open source vendor library that work with the same server-side driver. In that case, the server would return the names for both of the vendor libraries. The client would then try loading each vendor library as described below in Issue 3. 2) What order should the vendor names be returned in? RESOLVED: If there are multiple vendor names, then the client should use the names earlier in the list in preference to names later in the list. Specifically, the GLX client library will try to load and use each vendor name, in the order that the server lists them. It will stop when it finds the first vendor that works. 3) How are vendor names defined and interpreted? RESOLVED: The vendor names for a screen are defined based on the server's GLX implementation. Typically, a server will simply send the name of the driver that controls the screen. The GLX client library is responsible for translating the vendor name to a vendor library name. The details of the translation are part of the interface between the vendor library and the GLX client library, and so are not defined in this specification. 4) Does the vendor name list need a new enum? Could it be appended to the GLX_VENDOR string instead? RESOLVED: Use a new enum. The vendor-specific part of the GLX_VENDOR string is by definition arbitrary, even if in practice every most if not all GLX implementatinos leave it blank. In addition, using a new enum also makes parsing the string much easier. The client can simply pass the unmodified string to strtok or strtok_r. 5) Do we need to define the interaction with GLX_SGIX_pbuffer? RESOLVED. No. Any client or server that implements this extension will already support GLX 1.3, so using glXQueryDrawable to look up a screen number is sufficient. There's no harm if a server includes a GLX_SCREEN attribute in its GetDrawableAttributesSGIX reply, so a server is still free to use the same codepath for GetDrawableAttributesSGIX and glXGetDrawableAttributes. 6) Do we want to add GLX_SCREEN to the list of fbconfig attributes as well? RESOLVED: No. Adding GLX_SCREEN to glXGetFBConfigAttrib would be redundant, because a client can already find the screen number for a GLXFBConfig using glXGetVisualFromFBConfig and indirectly using glXGetFBConfigs. Revision History 1. 8 March 2016 - Initial draft.