Make the transition to script-genereated GLX code easier.

[mesa.git] / src / glx / x11 / glxcmds.c

/* $XFree86: xc/lib/GL/glx/glxcmds.c,v 1.30 2004/01/30 20:33:06 alanh Exp $ */
/*
** License Applicability. Except to the extent portions of this file are
** made subject to an alternative license as permitted in the SGI Free
** Software License B, Version 1.1 (the "License"), the contents of this
** file are subject only to the provisions of the License. You may not use
** this file except in compliance with the License. You may obtain a copy
** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
** 
** http://oss.sgi.com/projects/FreeB
** 
** Note that, as provided in the License, the Software is distributed on an
** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
** 
** Original Code. The Original Code is: OpenGL Sample Implementation,
** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
** Copyright in any portions created by third parties is as indicated
** elsewhere herein. All Rights Reserved.
** 
** Additional Notice Provisions: The application programming interfaces
** established by SGI in conjunction with the Original Code are The
** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
** Window System(R) (Version 1.3), released October 19, 1998. This software
** was created using the OpenGL(R) version 1.2.1 Sample Implementation
** published by SGI, but has not been independently verified as being
** compliant with the OpenGL(R) version 1.2.1 Specification.
**
*/

/**
 * \file glxcmds.c
 * Client-side GLX interface.
 */

#include <inttypes.h>
#include "glxclient.h"
#include <extutil.h>
#include <Xext.h>
#include <assert.h>
#include <string.h>
#include "glapi.h"
#ifdef GLX_DIRECT_RENDERING
#include "indirect_init.h"
#include "xf86vmode.h"
#endif
#include "glxextensions.h"
#include "glcontextmodes.h"
#include <sys/time.h>

#ifdef IN_DOXYGEN
#define GLX_PREFIX(x) x
#endif /* IN_DOXYGEN */

static const char __glXGLXClientVendorName[] = "SGI";
static const char __glXGLXClientVersion[] = "1.4";


#if defined(GLX_DIRECT_RENDERING)
#include "xf86dri.h"

static Bool __glXWindowExists(Display *dpy, GLXDrawable draw);

static void * DriverCreateContextWrapper( const __GLXscreenConfigs *psc,
    Display *dpy, XVisualInfo *vis, void *shared, __DRIcontext *ctx,
    const __GLcontextModes *fbconfig, int render_type );

static Bool dummyBindContext2( Display *dpy, int scrn,
    GLXDrawable draw, GLXDrawable read, GLXContext gc );

static Bool dummyUnbindContext2( Display *dpy, int scrn,
    GLXDrawable draw, GLXDrawable read, GLXContext gc );

/****************************************************************************/

/**
 * Used as glue when a driver does not support
 * \c __DRIcontextRec::bindContext2.
 * 
 * XXX .bindContext is only defined as a function pointer if
 * !DRI_NEW_INTERFACE_ONLY.
 *
 * \sa DriverCreateContextWrapper, __DRIcontextRec::bindContext2
 */
static Bool dummyBindContext2( Display *dpy, int scrn,
                               GLXDrawable draw, GLXDrawable read,
                               GLXContext gc )
{
    assert( draw == read );
    return (*gc->driContext.bindContext)( dpy, scrn, draw, gc );
}

/**
 * Used as glue when a driver does not support
 * \c __DRIcontextRec::unbindContext2.
 * 
 * XXX .unbindContext is only defined as a function pointer if
 * !DRI_NEW_INTERFACE_ONLY.
 *
 * \sa DriverCreateContextWrapper, __DRIcontextRec::unbindContext2
 */
static Bool dummyUnbindContext2( Display *dpy, int scrn,
                                 GLXDrawable draw, GLXDrawable read,
                                 GLXContext gc )
{
    assert( draw == read );
    return (*gc->driContext.unbindContext)( dpy, scrn, draw, gc, GL_FALSE );
}


/****************************************************************************/
/**
 * Wrap the call to the driver's \c createContext function.
 *
 * The \c createContext function is wrapped because not all drivers support
 * the "new" \c unbindContext2 and \c bindContext2 interfaces.  libGL should
 * not have to check to see which functions the driver supports.  Instead,
 * if either function is not supported it is wrapped.  The wrappers test to
 * make sure that both drawables are the same and pass control to the old
 * interface.
 *
 * \sa dummyBindContext2, dummyUnbindContext2,
 *      __DRIcontextRec::bindContext2, __DRIcontextRec::unbindContext2
 */

static void * DriverCreateContextWrapper( const __GLXscreenConfigs *psc,
                                          Display *dpy, XVisualInfo *vis,
                                          void *shared,
                                          __DRIcontext *ctx,
                                          const __GLcontextModes *modes,
                                          int render_type )
{
    void * ctx_priv = NULL;

    if ( psc->driScreen.createNewContext != NULL ) {
        assert( modes != NULL );
        ctx_priv = (*psc->driScreen.createNewContext)(dpy, modes, render_type,
                                                      shared, ctx);

        /* If the driver supports the createNewContext interface, then 
         * it MUST also support either the bindContext2 / unbindContext2
         * interface or the bindContext3 / unbindContext3 interface.
         */

        assert( (ctx_priv == NULL) || (ctx->unbindContext2 != NULL)
                || (ctx->unbindContext3 != NULL) );
        assert( (ctx_priv == NULL) || (ctx->bindContext2 != NULL)
                || (ctx->bindContext3 != NULL) );
    }
    else {
        if ( vis != NULL ) {
            ctx_priv = (*psc->driScreen.createContext)(dpy, vis, shared, ctx);

            if ( ctx_priv != NULL ) {
                if ( ctx->unbindContext2 == NULL ) {
                    ctx->unbindContext2 = dummyUnbindContext2;
                }

                if ( ctx->bindContext2 == NULL ) {
                    ctx->bindContext2 = dummyBindContext2;
                }
            }
        }
    }

    return ctx_priv;
}
#endif


/****************************************************************************/
/**
 * Get the __DRIdrawable for the drawable associated with a GLXContext
 * 
 * \param dpy       The display associated with \c drawable.
 * \param drawable  GLXDrawable whose __DRIdrawable part is to be retrieved.
 * \returns  A pointer to the context's __DRIdrawable on success, or NULL if
 *           the drawable is not associated with a direct-rendering context.
 */

#ifdef GLX_DIRECT_RENDERING
static __DRIdrawable *
GetDRIDrawable( Display *dpy, GLXDrawable drawable, int * const scrn_num )
{
    __GLXdisplayPrivate * const priv = __glXInitialize(dpy);

    if ( (priv != NULL) && (priv->driDisplay.private != NULL) ) {
        const unsigned  screen_count = ScreenCount(dpy);
        unsigned   i;

        for ( i = 0 ; i < screen_count ; i++ ) {
            __DRIscreen * const psc = &priv->screenConfigs[i].driScreen;
            __DRIdrawable * const pdraw = (psc->private != NULL)
               ? (*psc->getDrawable)(dpy, drawable, psc->private) : NULL;

            if ( pdraw != NULL ) {
                if ( scrn_num != NULL ) {
                    *scrn_num = i;
                }
                return pdraw;
            }
        }
    }

    return NULL;
}
#endif


/**
 * Get the GLX per-screen data structure associated with a GLX context.
 * 
 * \param dpy   Display for which the GLX per-screen information is to be
 *              retrieved.
 * \param scrn  Screen on \c dpy for which the GLX per-screen information is
 *              to be retrieved.
 * \returns A pointer to the GLX per-screen data if \c dpy and \c scrn
 *          specify a valid GLX screen, or NULL otherwise.
 * 
 * \todo Should this function validate that \c scrn is within the screen
 *       number range for \c dpy?
 */

static __GLXscreenConfigs *
GetGLXScreenConfigs(Display *dpy, int scrn)
{
    __GLXdisplayPrivate * const priv = __glXInitialize(dpy);

    return (priv->screenConfigs != NULL) ? &priv->screenConfigs[scrn] : NULL;
}


static int
GetGLXPrivScreenConfig( Display *dpy, int scrn, __GLXdisplayPrivate ** ppriv,
                        __GLXscreenConfigs ** ppsc )
{
    /* Initialize the extension, if needed .  This has the added value
     * of initializing/allocating the display private 
     */
    
    if ( dpy == NULL ) {
        return GLX_NO_EXTENSION;
    }

    *ppriv = __glXInitialize(dpy);
    if ( *ppriv == NULL ) {
        return GLX_NO_EXTENSION;
    }

    /* Check screen number to see if its valid */
    if ((scrn < 0) || (scrn >= ScreenCount(dpy))) {
        return GLX_BAD_SCREEN;
    }

    /* Check to see if the GL is supported on this screen */
    *ppsc = &((*ppriv)->screenConfigs[scrn]);
    if ( (*ppsc)->configs == NULL ) {
        /* No support for GL on this screen regardless of visual */
        return GLX_BAD_VISUAL;
    }

    return Success;
}


/**
 * Determine if a \c GLXFBConfig supplied by the application is valid.
 *
 * \param dpy     Application supplied \c Display pointer.
 * \param config  Application supplied \c GLXFBConfig.
 *
 * \returns If the \c GLXFBConfig is valid, the a pointer to the matching
 *          \c __GLcontextModes structure is returned.  Otherwise, \c NULL
 *          is returned.
 */
static __GLcontextModes *
ValidateGLXFBConfig( Display * dpy, GLXFBConfig config )
{
    __GLXdisplayPrivate * const priv = __glXInitialize(dpy);
    const unsigned num_screens = ScreenCount(dpy);
    unsigned   i;
    const __GLcontextModes * modes;


    if ( priv != NULL ) {
        for ( i = 0 ; i < num_screens ; i++ ) {
            for ( modes = priv->screenConfigs[i].configs
                  ; modes != NULL
                  ; modes = modes->next ) {
                if ( modes == (__GLcontextModes *) config ) {
                    return (__GLcontextModes *) config;
                }
            }
        }
    }

    return NULL;
}


/**
 * \todo It should be possible to move the allocate of \c client_state_private
 * later in the function for direct-rendering contexts.  Direct-rendering
 * contexts don't need to track client state, so they don't need that memory
 * at all.
 * 
 * \todo Eliminate \c __glXInitVertexArrayState.  Replace it with a new
 * function called \c __glXAllocateClientState that allocates the memory and
 * does all the initialization (including the pixel pack / unpack).
 */
static
GLXContext AllocateGLXContext( Display *dpy )
{
     GLXContext gc;
     int bufSize;
     CARD8 opcode;
    __GLXattribute *state;

    if (!dpy)
        return NULL;

    opcode = __glXSetupForCommand(dpy);
    if (!opcode) {
        return NULL;
    }

    /* Allocate our context record */
    gc = (GLXContext) Xmalloc(sizeof(struct __GLXcontextRec));
    if (!gc) {
        /* Out of memory */
        return NULL;
    }
    memset(gc, 0, sizeof(struct __GLXcontextRec));

    state = Xmalloc(sizeof(struct __GLXattributeRec));
    if (state == NULL) {
        /* Out of memory */
        Xfree(gc);
        return NULL;
    }
    gc->client_state_private = state;
    memset(gc->client_state_private, 0, sizeof(struct __GLXattributeRec));
    state->NoDrawArraysProtocol = (getenv("LIBGL_NO_DRAWARRAYS") != NULL);

    /*
    ** Create a temporary buffer to hold GLX rendering commands.  The size
    ** of the buffer is selected so that the maximum number of GLX rendering
    ** commands can fit in a single X packet and still have room in the X
    ** packet for the GLXRenderReq header.
    */

    bufSize = (XMaxRequestSize(dpy) * 4) - sz_xGLXRenderReq;
    gc->buf = (GLubyte *) Xmalloc(bufSize);
    if (!gc->buf) {
        Xfree(gc->client_state_private);
        Xfree(gc);
        return NULL;
    }
    gc->bufSize = bufSize;

    /* Fill in the new context */
    gc->renderMode = GL_RENDER;

    state->storePack.alignment = 4;
    state->storeUnpack.alignment = 4;

    __glXInitVertexArrayState(gc);

    gc->attributes.stackPointer = &gc->attributes.stack[0];

    /*
    ** PERFORMANCE NOTE: A mode dependent fill image can speed things up.
    ** Other code uses the fastImageUnpack bit, but it is never set
    ** to GL_TRUE.
    */
    gc->fastImageUnpack = GL_FALSE;
    gc->fillImage = __glFillImage;
    gc->isDirect = GL_FALSE;
    gc->pc = gc->buf;
    gc->bufEnd = gc->buf + bufSize;
    if (__glXDebug) {
        /*
        ** Set limit register so that there will be one command per packet
        */
        gc->limit = gc->buf;
    } else {
        gc->limit = gc->buf + bufSize - __GLX_BUFFER_LIMIT_SIZE;
    }
    gc->createDpy = dpy;
    gc->majorOpcode = opcode;

    /*
    ** Constrain the maximum drawing command size allowed to be
    ** transfered using the X_GLXRender protocol request.  First
    ** constrain by a software limit, then constrain by the protocl
    ** limit.
    */
    if (bufSize > __GLX_RENDER_CMD_SIZE_LIMIT) {
        bufSize = __GLX_RENDER_CMD_SIZE_LIMIT;
    }
    if (bufSize > __GLX_MAX_RENDER_CMD_SIZE) {
        bufSize = __GLX_MAX_RENDER_CMD_SIZE;
    }
    gc->maxSmallRenderCommandSize = bufSize;
    return gc;
}


/**
 * Create a new context.  Exactly one of \c vis and \c fbconfig should be
 * non-NULL.
 * 
 * \param use_glx_1_3  For FBConfigs, should GLX 1.3 protocol or
 *                     SGIX_fbconfig protocol be used?
 * \param renderType   For FBConfigs, what is the rendering type?
 */

static GLXContext
CreateContext(Display *dpy, XVisualInfo *vis,
              const __GLcontextModes * const fbconfig,
              GLXContext shareList,
              Bool allowDirect, GLXContextID contextID,
              Bool use_glx_1_3, int renderType)
{
    GLXContext gc;

    if ( dpy == NULL )
       return NULL;

    gc = AllocateGLXContext(dpy);
    if (!gc)
        return NULL;

    if (None == contextID) {
        if ( (vis == NULL) && (fbconfig == NULL) )
            return NULL;

#ifdef GLX_DIRECT_RENDERING
        if (allowDirect) {
            int screen = (fbconfig == NULL) ? vis->screen : fbconfig->screen;
            __GLXscreenConfigs * const psc = GetGLXScreenConfigs(dpy, screen);
            const __GLcontextModes * mode;

            /* The value of fbconfig cannot change because it is tested
             * later in the function.
             */
            if ( fbconfig == NULL ) {
                /* FIXME: Is it possible for the __GLcontextModes structure
                 * FIXME: to not be found?
                 */
                mode = _gl_context_modes_find_visual( psc->configs,
                                                      vis->visualid );
                assert( mode != NULL );
                assert( mode->screen == screen );
            }
            else {
                mode = fbconfig;
            }

            if (psc && psc->driScreen.private) {
                void * const shared = (shareList != NULL)
                    ? shareList->driContext.private : NULL;
                gc->driContext.private =
                    DriverCreateContextWrapper( psc, dpy, vis, shared,
                                                &gc->driContext, mode,
                                                renderType );
                if (gc->driContext.private) {
                    gc->isDirect = GL_TRUE;
                    gc->screen = mode->screen;
                    gc->vid = mode->visualID;
                    gc->fbconfigID = mode->fbconfigID;
                    gc->driContext.mode = mode;
                }
            }
        }
#endif

        LockDisplay(dpy);
        if ( fbconfig == NULL ) {
            xGLXCreateContextReq *req;

            /* Send the glXCreateContext request */
            GetReq(GLXCreateContext,req);
            req->reqType = gc->majorOpcode;
            req->glxCode = X_GLXCreateContext;
            req->context = gc->xid = XAllocID(dpy);
            req->visual = vis->visualid;
            req->screen = vis->screen;
            req->shareList = shareList ? shareList->xid : None;
            req->isDirect = gc->isDirect;
        }
        else if ( use_glx_1_3 ) {
            xGLXCreateNewContextReq *req;

            /* Send the glXCreateNewContext request */
            GetReq(GLXCreateNewContext,req);
            req->reqType = gc->majorOpcode;
            req->glxCode = X_GLXCreateNewContext;
            req->context = gc->xid = XAllocID(dpy);
            req->fbconfig = fbconfig->fbconfigID;
            req->screen = fbconfig->screen;
            req->renderType = renderType;
            req->shareList = shareList ? shareList->xid : None;
            req->isDirect = gc->isDirect;
        }
        else {
            xGLXVendorPrivateWithReplyReq *vpreq;
            xGLXCreateContextWithConfigSGIXReq *req;

            /* Send the glXCreateNewContext request */
            GetReqExtra(GLXVendorPrivateWithReply,
                        sz_xGLXCreateContextWithConfigSGIXReq-sz_xGLXVendorPrivateWithReplyReq,vpreq);
            req = (xGLXCreateContextWithConfigSGIXReq *)vpreq;
            req->reqType = gc->majorOpcode;
            req->glxCode = X_GLXVendorPrivateWithReply;
            req->vendorCode = X_GLXvop_CreateContextWithConfigSGIX;
            req->context = gc->xid = XAllocID(dpy);
            req->fbconfig = fbconfig->fbconfigID;
            req->screen = fbconfig->screen;
            req->renderType = renderType;
            req->shareList = shareList ? shareList->xid : None;
            req->isDirect = gc->isDirect;
        }

        UnlockDisplay(dpy);
        SyncHandle();
        gc->imported = GL_FALSE;
    }
    else {
        gc->xid = contextID;
        gc->imported = GL_TRUE;
    }

    return gc;
}


GLXContext GLX_PREFIX(glXCreateContext)(Display *dpy, XVisualInfo *vis,
                            GLXContext shareList, Bool allowDirect)
{
   return CreateContext(dpy, vis, NULL, shareList, allowDirect, None,
                        False, 0);
}

void __glXFreeContext(__GLXcontext *gc)
{
    if (gc->vendor) XFree((char *) gc->vendor);
    if (gc->renderer) XFree((char *) gc->renderer);
    if (gc->version) XFree((char *) gc->version);
    if (gc->extensions) XFree((char *) gc->extensions);
    __glFreeAttributeState(gc);
    XFree((char *) gc->buf);
    Xfree((char *) gc->client_state_private);
    XFree((char *) gc);
    
}

/*
** Destroy the named context
*/
static void 
DestroyContext(Display *dpy, GLXContext gc)
{
    xGLXDestroyContextReq *req;
    GLXContextID xid;
    CARD8 opcode;
    GLboolean imported;

    opcode = __glXSetupForCommand(dpy);
    if (!opcode || !gc) {
        return;
    }

    __glXLock();
    xid = gc->xid;
    imported = gc->imported;
    gc->xid = None;

#ifdef GLX_DIRECT_RENDERING
    /* Destroy the direct rendering context */
    if (gc->isDirect) {
        if (gc->driContext.private) {
            (*gc->driContext.destroyContext)(dpy, gc->screen,
                                             gc->driContext.private);
            gc->driContext.private = NULL;
        }
    }
#endif

    if (gc->currentDpy) {
        /* Have to free later cuz it's in use now */
        __glXUnlock();
    } else {
        /* Destroy the handle if not current to anybody */
        __glXUnlock();
        __glXFreeContext(gc);
    }

    if (!imported) {
        /* 
        ** This dpy also created the server side part of the context.
        ** Send the glXDestroyContext request.
        */
        LockDisplay(dpy);
        GetReq(GLXDestroyContext,req);
        req->reqType = opcode;
        req->glxCode = X_GLXDestroyContext;
        req->context = xid;
        UnlockDisplay(dpy);
        SyncHandle();
    }
}
void GLX_PREFIX(glXDestroyContext)(Display *dpy, GLXContext gc)
{
    DestroyContext(dpy, gc);
}

/*
** Return the major and minor version #s for the GLX extension
*/
Bool GLX_PREFIX(glXQueryVersion)(Display *dpy, int *major, int *minor)
{
    __GLXdisplayPrivate *priv;

    /* Init the extension.  This fetches the major and minor version. */
    priv = __glXInitialize(dpy);
    if (!priv) return GL_FALSE;

    if (major) *major = priv->majorVersion;
    if (minor) *minor = priv->minorVersion;
    return GL_TRUE;
}

/*
** Query the existance of the GLX extension
*/
Bool GLX_PREFIX(glXQueryExtension)(Display *dpy, int *errorBase, int *eventBase)
{
    int major_op, erb, evb;
    Bool rv;

    rv = XQueryExtension(dpy, GLX_EXTENSION_NAME, &major_op, &evb, &erb);
    if (rv) {
        if (errorBase) *errorBase = erb;
        if (eventBase) *eventBase = evb;
    }
    return rv;
}

/*
** Put a barrier in the token stream that forces the GL to finish its
** work before X can proceed.
*/
void GLX_PREFIX(glXWaitGL)(void)
{
    xGLXWaitGLReq *req;
    GLXContext gc = __glXGetCurrentContext();
    Display *dpy = gc->currentDpy;

    if (!dpy) return;

    /* Flush any pending commands out */
    __glXFlushRenderBuffer(gc, gc->pc);

#ifdef GLX_DIRECT_RENDERING
    if (gc->isDirect) {
/* This bit of ugliness unwraps the glFinish function */
#ifdef glFinish
#undef glFinish
#endif
        glFinish();
        return;
    }
#endif

    /* Send the glXWaitGL request */
    LockDisplay(dpy);
    GetReq(GLXWaitGL,req);
    req->reqType = gc->majorOpcode;
    req->glxCode = X_GLXWaitGL;
    req->contextTag = gc->currentContextTag;
    UnlockDisplay(dpy);
    SyncHandle();
}

/*
** Put a barrier in the token stream that forces X to finish its
** work before GL can proceed.
*/
void GLX_PREFIX(glXWaitX)(void)
{
    xGLXWaitXReq *req;
    GLXContext gc = __glXGetCurrentContext();
    Display *dpy = gc->currentDpy;

    if (!dpy) return;

    /* Flush any pending commands out */
    __glXFlushRenderBuffer(gc, gc->pc);

#ifdef GLX_DIRECT_RENDERING
    if (gc->isDirect) {
        XSync(dpy, False);
        return;
    }
#endif

    /*
    ** Send the glXWaitX request.
    */
    LockDisplay(dpy);
    GetReq(GLXWaitX,req);
    req->reqType = gc->majorOpcode;
    req->glxCode = X_GLXWaitX;
    req->contextTag = gc->currentContextTag;
    UnlockDisplay(dpy);
    SyncHandle();
}

void GLX_PREFIX(glXUseXFont)(Font font, int first, int count, int listBase)
{
    xGLXUseXFontReq *req;
    GLXContext gc = __glXGetCurrentContext();
    Display *dpy = gc->currentDpy;

    if (!dpy) return;

    /* Flush any pending commands out */
    (void) __glXFlushRenderBuffer(gc, gc->pc);

#ifdef GLX_DIRECT_RENDERING
    if (gc->isDirect) {
      DRI_glXUseXFont(font, first, count, listBase);
      return;
    }
#endif

    /* Send the glXUseFont request */
    LockDisplay(dpy);
    GetReq(GLXUseXFont,req);
    req->reqType = gc->majorOpcode;
    req->glxCode = X_GLXUseXFont;
    req->contextTag = gc->currentContextTag;
    req->font = font;
    req->first = first;
    req->count = count;
    req->listBase = listBase;
    UnlockDisplay(dpy);
    SyncHandle();
}

/************************************************************************/

/*
** Copy the source context to the destination context using the
** attribute "mask".
*/
void GLX_PREFIX(glXCopyContext)(Display *dpy, GLXContext source, GLXContext dest,
                    unsigned long mask)
{
    xGLXCopyContextReq *req;
    GLXContext gc = __glXGetCurrentContext();
    GLXContextTag tag;
    CARD8 opcode;

    opcode = __glXSetupForCommand(dpy);
    if (!opcode) {
        return;
    }

#ifdef GLX_DIRECT_RENDERING
    if (gc->isDirect) {
        /* NOT_DONE: This does not work yet */
    }
#endif

    /*
    ** If the source is the current context, send its tag so that the context
    ** can be flushed before the copy.
    */
    if (source == gc && dpy == gc->currentDpy) {
        tag = gc->currentContextTag;
    } else {
        tag = 0;
    }

    /* Send the glXCopyContext request */
    LockDisplay(dpy);
    GetReq(GLXCopyContext,req);
    req->reqType = opcode;
    req->glxCode = X_GLXCopyContext;
    req->source = source ? source->xid : None;
    req->dest = dest ? dest->xid : None;
    req->mask = mask;
    req->contextTag = tag;
    UnlockDisplay(dpy);
    SyncHandle();
}


/**
 * Determine if a context uses direct rendering.
 *
 * \param dpy        Display where the context was created.
 * \param contextID  ID of the context to be tested.
 *
 * \returns \c GL_TRUE if the context is direct rendering or not.
 */
static Bool __glXIsDirect(Display *dpy, GLXContextID contextID)
{
    xGLXIsDirectReq *req;
    xGLXIsDirectReply reply;
    CARD8 opcode;

    opcode = __glXSetupForCommand(dpy);
    if (!opcode) {
        return GL_FALSE;
    }

    /* Send the glXIsDirect request */
    LockDisplay(dpy);
    GetReq(GLXIsDirect,req);
    req->reqType = opcode;
    req->glxCode = X_GLXIsDirect;
    req->context = contextID;
    _XReply(dpy, (xReply*) &reply, 0, False);
    UnlockDisplay(dpy);
    SyncHandle();

    return reply.isDirect;
}

Bool GLX_PREFIX(glXIsDirect)(Display *dpy, GLXContext gc)
{
    if (!gc) {
        return GL_FALSE;
#ifdef GLX_DIRECT_RENDERING
    } else if (gc->isDirect) {
        return GL_TRUE;
#endif
    }
    return __glXIsDirect(dpy, gc->xid);
}

GLXPixmap GLX_PREFIX(glXCreateGLXPixmap)(Display *dpy, XVisualInfo *vis, Pixmap pixmap)
{
    xGLXCreateGLXPixmapReq *req;
    GLXPixmap xid;
    CARD8 opcode;

    opcode = __glXSetupForCommand(dpy);
    if (!opcode) {
        return None;
    }

    /* Send the glXCreateGLXPixmap request */
    LockDisplay(dpy);
    GetReq(GLXCreateGLXPixmap,req);
    req->reqType = opcode;
    req->glxCode = X_GLXCreateGLXPixmap;
    req->screen = vis->screen;
    req->visual = vis->visualid;
    req->pixmap = pixmap;
    req->glxpixmap = xid = XAllocID(dpy);
    UnlockDisplay(dpy);
    SyncHandle();
    return xid;
}

/*
** Destroy the named pixmap
*/
void GLX_PREFIX(glXDestroyGLXPixmap)(Display *dpy, GLXPixmap glxpixmap)
{
    xGLXDestroyGLXPixmapReq *req;
    CARD8 opcode;

    opcode = __glXSetupForCommand(dpy);
    if (!opcode) {
        return;
    }
    
    /* Send the glXDestroyGLXPixmap request */
    LockDisplay(dpy);
    GetReq(GLXDestroyGLXPixmap,req);
    req->reqType = opcode;
    req->glxCode = X_GLXDestroyGLXPixmap;
    req->glxpixmap = glxpixmap;
    UnlockDisplay(dpy);
    SyncHandle();
}

void GLX_PREFIX(glXSwapBuffers)(Display *dpy, GLXDrawable drawable)
{
    xGLXSwapBuffersReq *req;
    GLXContext gc;
    GLXContextTag tag;
    CARD8 opcode;
#ifdef GLX_DIRECT_RENDERING
    __DRIdrawable *pdraw = GetDRIDrawable( dpy, drawable, NULL );

    if ( pdraw != NULL ) {
        (*pdraw->swapBuffers)(dpy, pdraw->private);
        return;
    }
#endif

    opcode = __glXSetupForCommand(dpy);
    if (!opcode) {
        return;
    }

    /*
    ** The calling thread may or may not have a current context.  If it
    ** does, send the context tag so the server can do a flush.
    */
    gc = __glXGetCurrentContext();
    if ((gc != NULL) && (dpy == gc->currentDpy) && 
        ((drawable == gc->currentDrawable) || (drawable == gc->currentReadable)) ) {
        tag = gc->currentContextTag;
    } else {
        tag = 0;
    }

    /* Send the glXSwapBuffers request */
    LockDisplay(dpy);
    GetReq(GLXSwapBuffers,req);
    req->reqType = opcode;
    req->glxCode = X_GLXSwapBuffers;
    req->drawable = drawable;
    req->contextTag = tag;
    UnlockDisplay(dpy);
    SyncHandle();
    XFlush(dpy);
}


/*
** Return configuration information for the given display, screen and
** visual combination.
*/
int GLX_PREFIX(glXGetConfig)(Display *dpy, XVisualInfo *vis, int attribute,
                 int *value_return)
{
    __GLXdisplayPrivate *priv;
    __GLXscreenConfigs *psc;
    int   status;

    status = GetGLXPrivScreenConfig( dpy, vis->screen, & priv, & psc );
    if ( status == Success ) {
        const __GLcontextModes * const modes = _gl_context_modes_find_visual(
                                             psc->configs, vis->visualid );

        /* Lookup attribute after first finding a match on the visual */
        if ( modes != NULL ) {
            return _gl_get_context_mode_data( modes, attribute, value_return );
        }
        
        status = GLX_BAD_VISUAL;
    }

    /*
    ** If we can't find the config for this visual, this visual is not
    ** supported by the OpenGL implementation on the server.
    */
    if ( (status == GLX_BAD_VISUAL) && (attribute == GLX_USE_GL) ) {
        *value_return = GL_FALSE;
        status = Success;
    }

    return status;
}

/************************************************************************/

static void
init_fbconfig_for_chooser( __GLcontextModes * config,
                           GLboolean fbconfig_style_tags )
{
    memset( config, 0, sizeof( __GLcontextModes ) );
    config->visualID = (XID) GLX_DONT_CARE;
    config->visualType = GLX_DONT_CARE;

    /* glXChooseFBConfig specifies different defaults for these two than
     * glXChooseVisual.
     */
    if ( fbconfig_style_tags ) {
        config->rgbMode = GL_TRUE;
        config->doubleBufferMode = GLX_DONT_CARE;
    }

    config->visualRating = GLX_DONT_CARE;
    config->transparentPixel = GLX_NONE;
    config->transparentRed = GLX_DONT_CARE;
    config->transparentGreen = GLX_DONT_CARE;
    config->transparentBlue = GLX_DONT_CARE;
    config->transparentAlpha = GLX_DONT_CARE;
    config->transparentIndex = GLX_DONT_CARE;

    config->drawableType = GLX_WINDOW_BIT;
    config->renderType = (config->rgbMode) ? GLX_RGBA_BIT : GLX_COLOR_INDEX_BIT;
    config->xRenderable = GLX_DONT_CARE;
    config->fbconfigID = (GLXFBConfigID)(GLX_DONT_CARE);

    config->swapMethod = GLX_DONT_CARE;
}

#define MATCH_DONT_CARE( param ) \
        do { \
            if ( (a-> param != GLX_DONT_CARE) \
                 && (a-> param != b-> param) ) { \
                return False; \
            } \
        } while ( 0 )

#define MATCH_MINIMUM( param ) \
        do { \
            if ( (a-> param != GLX_DONT_CARE) \
                 && (a-> param > b-> param) ) { \
                return False; \
            } \
        } while ( 0 )

#define MATCH_EXACT( param ) \
        do { \
            if ( a-> param != b-> param) { \
                return False; \
            } \
        } while ( 0 )

/**
 * Determine if two GLXFBConfigs are compatible.
 *
 * \param a  Application specified config to test.
 * \param b  Server specified config to test against \c a.
 */
static Bool
fbconfigs_compatible( const __GLcontextModes * const a,
                      const __GLcontextModes * const b )
{
    MATCH_DONT_CARE( doubleBufferMode );
    MATCH_DONT_CARE( visualType );
    MATCH_DONT_CARE( visualRating );
    MATCH_DONT_CARE( xRenderable );
    MATCH_DONT_CARE( fbconfigID );
    MATCH_DONT_CARE( swapMethod );

    MATCH_MINIMUM( rgbBits );
    MATCH_MINIMUM( numAuxBuffers );
    MATCH_MINIMUM( redBits );
    MATCH_MINIMUM( greenBits );
    MATCH_MINIMUM( blueBits );
    MATCH_MINIMUM( alphaBits );
    MATCH_MINIMUM( depthBits );
    MATCH_MINIMUM( stencilBits );
    MATCH_MINIMUM( accumRedBits );
    MATCH_MINIMUM( accumGreenBits );
    MATCH_MINIMUM( accumBlueBits );
    MATCH_MINIMUM( accumAlphaBits );
    MATCH_MINIMUM( sampleBuffers );
    MATCH_MINIMUM( maxPbufferWidth );
    MATCH_MINIMUM( maxPbufferHeight );
    MATCH_MINIMUM( maxPbufferPixels );
    MATCH_MINIMUM( samples );

    MATCH_DONT_CARE( stereoMode );
    MATCH_EXACT( level );

    if ( ((a->drawableType & b->drawableType) == 0)
         || ((a->renderType & b->renderType) == 0) ) {
        return False;
    }


    /* There is a bug in a few of the XFree86 DDX drivers.  They contain
     * visuals with a "transparent type" of 0 when they really mean GLX_NONE.
     * Technically speaking, it is a bug in the DDX driver, but there is
     * enough of an installed base to work around the problem here.  In any
     * case, 0 is not a valid value of the transparent type, so we'll treat 0 
     * from the app as GLX_DONT_CARE. We'll consider GLX_NONE from the app and
     * 0 from the server to be a match to maintain backward compatibility with
     * the (broken) drivers.
     */

    if ( a->transparentPixel != GLX_DONT_CARE
         && a->transparentPixel != 0 ) {
        if ( a->transparentPixel == GLX_NONE ) {
            if ( b->transparentPixel != GLX_NONE && b->transparentPixel != 0 )
                return False;
        } else {
            MATCH_EXACT( transparentPixel );
        }

        switch ( a->transparentPixel ) {
          case GLX_TRANSPARENT_RGB:
            MATCH_DONT_CARE( transparentRed );
            MATCH_DONT_CARE( transparentGreen );
            MATCH_DONT_CARE( transparentBlue );
            MATCH_DONT_CARE( transparentAlpha );
            break;

          case GLX_TRANSPARENT_INDEX:
            MATCH_DONT_CARE( transparentIndex );
            break;

          default:
            break;
        }
    }

    return True;
}


/* There's some trickly language in the GLX spec about how this is supposed
 * to work.  Basically, if a given component size is either not specified
 * or the requested size is zero, it is supposed to act like PERFER_SMALLER.
 * Well, that's really hard to do with the code as-is.  This behavior is
 * closer to correct, but still not technically right.
 */
#define PREFER_LARGER_OR_ZERO(comp) \
    do { \
        if ( ((*a)-> comp) != ((*b)-> comp) ) { \
            if ( ((*a)-> comp) == 0 ) { \
                return -1; \
            } \
            else if ( ((*b)-> comp) == 0 ) { \
                return 1; \
            } \
            else { \
                return ((*b)-> comp) - ((*a)-> comp) ; \
            } \
        } \
    } while( 0 )

#define PREFER_LARGER(comp) \
    do { \
        if ( ((*a)-> comp) != ((*b)-> comp) ) { \
            return ((*b)-> comp) - ((*a)-> comp) ; \
        } \
    } while( 0 )

#define PREFER_SMALLER(comp) \
    do { \
        if ( ((*a)-> comp) != ((*b)-> comp) ) { \
            return ((*a)-> comp) - ((*b)-> comp) ; \
        } \
    } while( 0 )

/**
 * Compare two GLXFBConfigs.  This function is intended to be used as the
 * compare function passed in to qsort.
 * 
 * \returns If \c a is a "better" config, according to the specification of
 *          SGIX_fbconfig, a number less than zero is returned.  If \c b is
 *          better, then a number greater than zero is return.  If both are
 *          equal, zero is returned.
 * \sa qsort, glXChooseVisual, glXChooseFBConfig, glXChooseFBConfigSGIX
 */
static int
fbconfig_compare( const __GLcontextModes * const * const a,
                  const __GLcontextModes * const * const b )
{
    /* The order of these comparisons must NOT change.  It is defined by
     * the GLX 1.3 spec and ARB_multisample.
     */

    PREFER_SMALLER( visualSelectGroup );

    /* The sort order for the visualRating is GLX_NONE, GLX_SLOW, and
     * GLX_NON_CONFORMANT_CONFIG.  It just so happens that this is the
     * numerical sort order of the enums (0x8000, 0x8001, and 0x800D).
     */
    PREFER_SMALLER( visualRating );

    /* This isn't quite right.  It is supposed to compare the sum of the
     * components the user specifically set minimums for.
     */
    PREFER_LARGER_OR_ZERO( redBits );
    PREFER_LARGER_OR_ZERO( greenBits );
    PREFER_LARGER_OR_ZERO( blueBits );
    PREFER_LARGER_OR_ZERO( alphaBits );

    PREFER_SMALLER( rgbBits );

    if ( ((*a)->doubleBufferMode != (*b)->doubleBufferMode) ) {
        /* Prefer single-buffer.
         */
        return ( !(*a)->doubleBufferMode ) ? -1 : 1;
    }

    PREFER_SMALLER( numAuxBuffers );

    PREFER_LARGER_OR_ZERO( depthBits );
    PREFER_SMALLER( stencilBits );

    /* This isn't quite right.  It is supposed to compare the sum of the
     * components the user specifically set minimums for.
     */
    PREFER_LARGER_OR_ZERO( accumRedBits );
    PREFER_LARGER_OR_ZERO( accumGreenBits );
    PREFER_LARGER_OR_ZERO( accumBlueBits );
    PREFER_LARGER_OR_ZERO( accumAlphaBits );

    PREFER_SMALLER( visualType );

    /* None of the multisample specs say where this comparison should happen,
     * so I put it near the end.
     */
    PREFER_SMALLER( sampleBuffers );
    PREFER_SMALLER( samples );

    /* None of the pbuffer or fbconfig specs say that this comparison needs
     * to happen at all, but it seems like it should.
     */
    PREFER_LARGER( maxPbufferWidth );
    PREFER_LARGER( maxPbufferHeight );
    PREFER_LARGER( maxPbufferPixels );

    return 0;
}


/**
 * Selects and sorts a subset of the supplied configs based on the attributes.
 * This function forms to basis of \c glXChooseVisual, \c glXChooseFBConfig,
 * and \c glXChooseFBConfigSGIX.
 * 
 * \param configs   Array of pointers to possible configs.  The elements of
 *                  this array that do not meet the criteria will be set to
 *                  NULL.  The remaining elements will be sorted according to
 *                  the various visual / FBConfig selection rules.
 * \param num_configs  Number of elements in the \c configs array.
 * \param attribList   Attributes used select from \c configs.  This array is
 *                     terminated by a \c None tag.  The array can either take
 *                     the form expected by \c glXChooseVisual (where boolean
 *                     tags do not have a value) or by \c glXChooseFBConfig
 *                     (where every tag has a value).
 * \param fbconfig_style_tags  Selects whether \c attribList is in
 *                             \c glXChooseVisual style or
 *                             \c glXChooseFBConfig style.
 * \returns The number of valid elements left in \c configs.
 * 
 * \sa glXChooseVisual, glXChooseFBConfig, glXChooseFBConfigSGIX
 */
static int
choose_visual( __GLcontextModes ** configs, int num_configs,
               const int *attribList, GLboolean fbconfig_style_tags )
{
    __GLcontextModes    test_config;
    int   base;
    int   i;

    /* This is a fairly direct implementation of the selection method
     * described by GLX_SGIX_fbconfig.  Start by culling out all the
     * configs that are not compatible with the selected parameter
     * list.
     */

    init_fbconfig_for_chooser( & test_config, fbconfig_style_tags );
    __glXInitializeVisualConfigFromTags( & test_config, 512,
                                         (const INT32 *) attribList,
                                         GL_TRUE, fbconfig_style_tags );

    base = 0;
    for ( i = 0 ; i < num_configs ; i++ ) {
        if ( fbconfigs_compatible( & test_config, configs[i] ) ) {
            configs[ base ] = configs[ i ];
            base++;
        }
    }

    if ( base == 0 ) {
        return 0;
    }
 
    if ( base < num_configs ) {
        (void) memset( & configs[ base ], 0, 
                       sizeof( void * ) * (num_configs - base) );
    }

    /* After the incompatible configs are removed, the resulting
     * list is sorted according to the rules set out in the various
     * specifications.
     */
    
    qsort( configs, base, sizeof( __GLcontextModes * ),
           (int (*)(const void*, const void*)) fbconfig_compare );
    return base;
}




/*
** Return the visual that best matches the template.  Return None if no
** visual matches the template.
*/
XVisualInfo *GLX_PREFIX(glXChooseVisual)(Display *dpy, int screen, int *attribList)
{
    XVisualInfo *visualList = NULL;
    __GLXdisplayPrivate *priv;
    __GLXscreenConfigs *psc;
    __GLcontextModes  test_config;
    __GLcontextModes *modes;
    const __GLcontextModes *best_config = NULL;

    /*
    ** Get a list of all visuals, return if list is empty
    */
    if ( GetGLXPrivScreenConfig( dpy, screen, & priv, & psc ) != Success ) {
        return None;
    }
   

    /*
    ** Build a template from the defaults and the attribute list
    ** Free visual list and return if an unexpected token is encountered
    */
    init_fbconfig_for_chooser( & test_config, GL_FALSE );
    __glXInitializeVisualConfigFromTags( & test_config, 512, 
                                         (const INT32 *) attribList,
                                         GL_TRUE, GL_FALSE );

    /*
    ** Eliminate visuals that don't meet minimum requirements
    ** Compute a score for those that do
    ** Remember which visual, if any, got the highest score
    */
    for ( modes = psc->configs ; modes != NULL ; modes = modes->next ) {
        if ( fbconfigs_compatible( & test_config, modes )
             && ((best_config == NULL)
                 || (fbconfig_compare( (const __GLcontextModes * const * const)&modes, &best_config ) < 0)) ) {
            best_config = modes;
        }
    }

    /*
    ** If no visual is acceptable, return None
    ** Otherwise, create an XVisualInfo list with just the selected X visual
    ** and return this.
    */
    if (best_config != NULL) {
        XVisualInfo visualTemplate;
        int  i;

        visualTemplate.screen = screen;
        visualTemplate.visualid = best_config->visualID;
        visualList = XGetVisualInfo( dpy, VisualScreenMask|VisualIDMask,
                                     &visualTemplate, &i );
    }

    return visualList;
}


const char *GLX_PREFIX(glXQueryExtensionsString)( Display *dpy, int screen )
{
    __GLXscreenConfigs *psc;
    __GLXdisplayPrivate *priv;

    if ( GetGLXPrivScreenConfig( dpy, screen, & priv, & psc ) != Success ) {
        return NULL;
    }

    if (!psc->effectiveGLXexts) {
        if (!psc->serverGLXexts) {
            psc->serverGLXexts = __glXGetStringFromServer(dpy, priv->majorOpcode,
                                                   X_GLXQueryServerString,
                                                   screen, GLX_EXTENSIONS);
        }

        __glXCalculateUsableExtensions(psc,
#ifdef GLX_DIRECT_RENDERING
                                       (priv->driDisplay.private != NULL),
#else
                                       GL_FALSE,
#endif
                                       priv->minorVersion);
    }

    return psc->effectiveGLXexts;
}

const char *GLX_PREFIX(glXGetClientString)( Display *dpy, int name )
{
    switch(name) {
        case GLX_VENDOR:
            return (__glXGLXClientVendorName);
        case GLX_VERSION:
            return (__glXGLXClientVersion);
        case GLX_EXTENSIONS:
            return (__glXGetClientExtensions());
        default:
            return NULL;
    }
}

const char *GLX_PREFIX(glXQueryServerString)( Display *dpy, int screen, int name )
{
    __GLXscreenConfigs *psc;
    __GLXdisplayPrivate *priv;
    const char ** str;


    if ( GetGLXPrivScreenConfig( dpy, screen, & priv, & psc ) != Success ) {
        return NULL;
    }

    switch(name) {
        case GLX_VENDOR:
            str = & priv->serverGLXvendor;
            break;
        case GLX_VERSION:
            str = & priv->serverGLXversion;
            break;
        case GLX_EXTENSIONS:
            str = & psc->serverGLXexts;
            break;
        default:
            return NULL;
    }

    if ( *str == NULL ) {
        *str = __glXGetStringFromServer(dpy, priv->majorOpcode,
                                        X_GLXQueryServerString, screen, name);
    }
    
    return *str;
}

void __glXClientInfo (  Display *dpy, int opcode  )
{
    xGLXClientInfoReq *req;
    int size;
    char * ext_str = __glXGetClientGLExtensionString();

    /* Send the glXClientInfo request */
    LockDisplay(dpy);
    GetReq(GLXClientInfo,req);
    req->reqType = opcode;
    req->glxCode = X_GLXClientInfo;
    req->major = GLX_MAJOR_VERSION;
    req->minor = GLX_MINOR_VERSION;

    size = strlen( ext_str ) + 1;
    req->length += (size + 3) >> 2;
    req->numbytes = size;
    Data(dpy, ext_str, size);

    UnlockDisplay(dpy);
    SyncHandle();
    
    Xfree( ext_str );
}


/*
** EXT_import_context
*/

Display *glXGetCurrentDisplay(void)
{
    GLXContext gc = __glXGetCurrentContext();
    if (NULL == gc) return NULL;
    return gc->currentDpy;
}

GLX_ALIAS(Display *, glXGetCurrentDisplayEXT, (void), (),
          glXGetCurrentDisplay)

/**
 * Used internally by libGL to send \c xGLXQueryContextinfoExtReq requests
 * to the X-server.
 * 
 * \param dpy  Display where \c ctx was created.
 * \param ctx  Context to query.
 * \returns  \c Success on success.  \c GLX_BAD_CONTEXT if \c ctx is invalid,
 *           or zero if the request failed due to internal problems (i.e.,
 *           unable to allocate temporary memory, etc.)
 * 
 * \note
 * This function dynamically determines whether to use the EXT_import_context
 * version of the protocol or the GLX 1.3 version of the protocol.
 */
static int __glXQueryContextInfo(Display *dpy, GLXContext ctx)
{
    __GLXdisplayPrivate *priv = __glXInitialize(dpy);
    xGLXQueryContextReply reply;
    CARD8 opcode;
    GLuint numValues;
    int retval;

    if (ctx == NULL) {
        return GLX_BAD_CONTEXT;
    }
    opcode = __glXSetupForCommand(dpy);
    if (!opcode) {
        return 0;
    }

    /* Send the glXQueryContextInfoEXT request */
    LockDisplay(dpy);

    if ( (priv->majorVersion > 1) || (priv->minorVersion >= 3) ) {
        xGLXQueryContextReq *req;

        GetReq(GLXQueryContext, req);

        req->reqType = opcode;
        req->glxCode = X_GLXQueryContext;
        req->context = (unsigned int)(ctx->xid);
    }
    else {
        xGLXVendorPrivateReq *vpreq;
        xGLXQueryContextInfoEXTReq *req;

        GetReqExtra( GLXVendorPrivate,
                     sz_xGLXQueryContextInfoEXTReq - sz_xGLXVendorPrivateReq,
                     vpreq );
        req = (xGLXQueryContextInfoEXTReq *)vpreq;
        req->reqType = opcode;
        req->glxCode = X_GLXVendorPrivateWithReply;
        req->vendorCode = X_GLXvop_QueryContextInfoEXT;
        req->context = (unsigned int)(ctx->xid);
    }

    _XReply(dpy, (xReply*) &reply, 0, False);

    numValues = reply.n;
    if (numValues == 0)
        retval = Success;
    else if (numValues > __GLX_MAX_CONTEXT_PROPS)
        retval = 0;
    else
    {
        int *propList, *pProp;
        int nPropListBytes;
        int i;

        nPropListBytes = numValues << 3;
        propList = (int *) Xmalloc(nPropListBytes);
        if (NULL == propList) {
            retval = 0;
        } else {
            _XRead(dpy, (char *)propList, nPropListBytes);
            pProp = propList;
            for (i=0; i < numValues; i++) {
                switch (*pProp++) {
                case GLX_SHARE_CONTEXT_EXT:
                    ctx->share_xid = *pProp++;
                    break;
                case GLX_VISUAL_ID_EXT:
                    ctx->vid = *pProp++;
                    break;
                case GLX_SCREEN:
                    ctx->screen = *pProp++;
                    break;
                case GLX_FBCONFIG_ID:
                    ctx->fbconfigID = *pProp++;
                    break;
                case GLX_RENDER_TYPE:
                    ctx->renderType = *pProp++;
                    break;
                default:
                    pProp++;
                    continue;
                }
            }
            Xfree((char *)propList);
            retval = Success;
        }
    }
    UnlockDisplay(dpy);
    SyncHandle();
    return retval;
}

int
GLX_PREFIX(glXQueryContext)(Display *dpy, GLXContext ctx,
                            int attribute, int *value)
{
    int retVal;

    /* get the information from the server if we don't have it already */
    if (!ctx->isDirect && (ctx->vid == None)) {
        retVal = __glXQueryContextInfo(dpy, ctx);
        if (Success != retVal) return retVal;
    }
    switch (attribute) {
    case GLX_SHARE_CONTEXT_EXT:
        *value = (int)(ctx->share_xid);
        break;
    case GLX_VISUAL_ID_EXT:
        *value = (int)(ctx->vid);
        break;
    case GLX_SCREEN:
        *value = (int)(ctx->screen);
        break;
    case GLX_FBCONFIG_ID:
        *value = (int)(ctx->fbconfigID);
        break;
    case GLX_RENDER_TYPE:
        *value = (int)(ctx->renderType);
        break;
    default:
        return GLX_BAD_ATTRIBUTE;
    }
    return Success;
}

GLX_ALIAS( int, glXQueryContextInfoEXT,
           (Display *dpy, GLXContext ctx, int attribute, int *value),
           (dpy, ctx, attribute, value),
           glXQueryContext )

GLXContextID glXGetContextIDEXT(const GLXContext ctx)
{
    return ctx->xid;
}

GLXContext GLX_PREFIX(glXImportContextEXT)(Display *dpy, GLXContextID contextID)
{
    GLXContext ctx;

    if (contextID == None) {
        return NULL;
    }
    if (__glXIsDirect(dpy, contextID)) {
        return NULL;
    }

    ctx = CreateContext(dpy, NULL, NULL, NULL, False, contextID, False, 0);
    if (NULL != ctx) {
        if (Success != __glXQueryContextInfo(dpy, ctx)) {
           return NULL;
        }
    }
    return ctx;
}

void GLX_PREFIX(glXFreeContextEXT)(Display *dpy, GLXContext ctx)
{
    DestroyContext(dpy, ctx);
}



/*
 * GLX 1.3 functions - these are just stubs for now!
 */

GLXFBConfig *GLX_PREFIX(glXChooseFBConfig)(Display *dpy, int screen, const int *attribList, int *nitems)
{
    __GLcontextModes ** config_list;
    int   list_size;


    config_list = (__GLcontextModes **) 
        GLX_PREFIX(glXGetFBConfigs)( dpy, screen, & list_size );

    if ( (config_list != NULL) && (list_size > 0) ) {
        list_size = choose_visual( config_list, list_size, attribList,
                                   GL_TRUE );
        if ( list_size == 0 ) {
            XFree( config_list );
            config_list = NULL;
        }
    }

    *nitems = list_size;
    return (GLXFBConfig *) config_list;
}


GLXContext GLX_PREFIX(glXCreateNewContext)(Display *dpy, GLXFBConfig config, int renderType, GLXContext shareList, Bool allowDirect)
{
    return CreateContext( dpy, NULL, (__GLcontextModes *) config, shareList,
                          allowDirect, None, True, renderType );
}


GLXDrawable GLX_PREFIX(glXGetCurrentReadDrawable)(void)
{
    GLXContext gc = __glXGetCurrentContext();
    return gc->currentReadable;
}


GLXFBConfig *GLX_PREFIX(glXGetFBConfigs)(Display *dpy, int screen, int *nelements)
{
    __GLXdisplayPrivate *priv = __glXInitialize(dpy);
    __GLcontextModes ** config = NULL;
    int   i;

    if ( (priv->screenConfigs != NULL)
         && (screen >= 0) && (screen <= ScreenCount(dpy))
         && (priv->screenConfigs[screen].configs != NULL)
         && (priv->screenConfigs[screen].configs->fbconfigID != GLX_DONT_CARE) ) {
        unsigned num_configs = 0;
        __GLcontextModes * modes;


        for ( modes = priv->screenConfigs[screen].configs
              ; modes != NULL
              ; modes = modes->next ) {
            if ( modes->fbconfigID != GLX_DONT_CARE ) {
                num_configs++;
            }
        }

        config = (__GLcontextModes **) Xmalloc( sizeof(__GLcontextModes *)
                                                * num_configs );
        if ( config != NULL ) {
            *nelements = num_configs;
            i = 0;
            for ( modes = priv->screenConfigs[screen].configs
                  ; modes != NULL
                  ; modes = modes->next ) {
                config[i] = modes;
                i++;
            }
        }
    }
    return (GLXFBConfig *) config;
}


int GLX_PREFIX(glXGetFBConfigAttrib)(Display *dpy, GLXFBConfig config, int attribute, int *value)
{
    __GLcontextModes * const modes = ValidateGLXFBConfig( dpy, config );

    return (modes != NULL)
        ? _gl_get_context_mode_data( modes, attribute, value )
        : GLXBadFBConfig;
}


XVisualInfo *GLX_PREFIX(glXGetVisualFromFBConfig)(Display *dpy, GLXFBConfig config)
{
    XVisualInfo visualTemplate;
    __GLcontextModes * fbconfig = (__GLcontextModes *) config;
    int  count;

    /*
    ** Get a list of all visuals, return if list is empty
    */
    visualTemplate.visualid = fbconfig->visualID;
    return XGetVisualInfo(dpy,VisualIDMask,&visualTemplate,&count);
}


/*
** GLX_SGI_make_current_read
*/

GLX_ALIAS(GLXDrawable, glXGetCurrentReadDrawableSGI, (void), (),
          glXGetCurrentReadDrawable)


/*
** GLX_SGI_swap_control
*/
int GLX_PREFIX(glXSwapIntervalSGI)(int interval)
{
   xGLXVendorPrivateReq *req;
   GLXContext gc = __glXGetCurrentContext();
   Display * dpy;
   CARD32 * interval_ptr;
   CARD8 opcode;

   if ( gc == NULL ) {
      return GLX_BAD_CONTEXT;
   }
   
   if ( interval <= 0 ) {
      return GLX_BAD_VALUE;
   }

#ifdef GLX_DIRECT_RENDERING
   if ( gc->isDirect ) {
       __GLXscreenConfigs * const psc = GetGLXScreenConfigs( gc->currentDpy,
                                                             gc->screen );
       __DRIdrawable * const pdraw = GetDRIDrawable( gc->currentDpy,
                                                     gc->currentDrawable,
                                                     NULL );
       if ( __glXExtensionBitIsEnabled( psc, SGI_swap_control_bit )
            && (pdraw != NULL) ) {
           pdraw->swap_interval = interval;
           return 0;
       }
       else {
           return GLX_BAD_CONTEXT;
       }
   }
#endif
   dpy = gc->currentDpy;
   opcode = __glXSetupForCommand(dpy);
   if (!opcode) {
      return 0;
   }

   /* Send the glXSwapIntervalSGI request */
   LockDisplay(dpy);
   GetReqExtra(GLXVendorPrivate,sizeof(CARD32),req);
   req->reqType = opcode;
   req->glxCode = X_GLXVendorPrivate;
   req->vendorCode = X_GLXvop_SwapIntervalSGI;
   req->contextTag = gc->currentContextTag;

   interval_ptr = (CARD32 *) req + 1;
   *interval_ptr = interval;

   UnlockDisplay(dpy);
   SyncHandle();
   XFlush(dpy);

   return 0;
}


/*
** GLX_MESA_swap_control
*/
GLint GLX_PREFIX(glXSwapIntervalMESA)(unsigned interval)
{
#ifdef GLX_DIRECT_RENDERING
   GLXContext gc = __glXGetCurrentContext();

   if ( interval < 0 ) {
      return GLX_BAD_VALUE;
   }

   if ( (gc != NULL) && gc->isDirect ) {
      __GLXscreenConfigs * const psc = GetGLXScreenConfigs( gc->currentDpy,
                                                            gc->screen );
      
      if ( (psc != NULL) && (psc->driScreen.private != NULL)
           && __glXExtensionBitIsEnabled( psc, MESA_swap_control_bit ) ) {
         __DRIdrawable * const pdraw = 
             (*psc->driScreen.getDrawable)(gc->currentDpy,
                                           gc->currentDrawable,
                                           psc->driScreen.private);
         if ( pdraw != NULL ) {
            pdraw->swap_interval = interval;
            return 0;
         }
      }
   }
#else
   (void) interval;
#endif

   return GLX_BAD_CONTEXT;
}
 
GLint GLX_PREFIX(glXGetSwapIntervalMESA)( void )
{
#ifdef GLX_DIRECT_RENDERING
   GLXContext gc = __glXGetCurrentContext();

   if ( (gc != NULL) && gc->isDirect ) {
      __GLXscreenConfigs * const psc = GetGLXScreenConfigs( gc->currentDpy,
                                                            gc->screen );
      
      if ( (psc != NULL) && (psc->driScreen.private != NULL)
           && __glXExtensionBitIsEnabled( psc, MESA_swap_control_bit ) ) {
         __DRIdrawable * const pdraw = 
             (*psc->driScreen.getDrawable)(gc->currentDpy,
                                           gc->currentDrawable,
                                           psc->driScreen.private);
         if ( pdraw != NULL ) {
            return pdraw->swap_interval;
         }
      }
   }
#endif

   return 0;
}


/*
** GLX_MESA_swap_frame_usage
*/

GLint GLX_PREFIX(glXBeginFrameTrackingMESA)(Display *dpy, GLXDrawable drawable)
{
   int   status = GLX_BAD_CONTEXT;
#ifdef GLX_DIRECT_RENDERING
   int screen;
   __DRIdrawable * const pdraw = GetDRIDrawable(dpy, drawable, & screen);
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs(dpy, screen);

   if ( (pdraw != NULL) && (pdraw->frameTracking != NULL)
        && __glXExtensionBitIsEnabled( psc, MESA_swap_frame_usage_bit ) ) {
      status = pdraw->frameTracking( dpy, pdraw->private, GL_TRUE );
   }
#else
   (void) dpy;
   (void) drawable;
#endif
   return status;
}

    
GLint GLX_PREFIX(glXEndFrameTrackingMESA)(Display *dpy, GLXDrawable drawable)
{
   int   status = GLX_BAD_CONTEXT;
#ifdef GLX_DIRECT_RENDERING
   int screen;
   __DRIdrawable * const pdraw = GetDRIDrawable(dpy, drawable, & screen);
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs(dpy, screen);

   if ( (pdraw != NULL) && (pdraw->frameTracking != NULL)
        && __glXExtensionBitIsEnabled( psc, MESA_swap_frame_usage_bit ) ) {
      status = pdraw->frameTracking( dpy, pdraw->private, GL_FALSE );
   }
#else
   (void) dpy;
   (void) drawable;
#endif
   return status;
}


GLint GLX_PREFIX(glXGetFrameUsageMESA)(Display *dpy, GLXDrawable drawable,
                                       GLfloat *usage)
{
   int   status = GLX_BAD_CONTEXT;
#ifdef GLX_DIRECT_RENDERING
   int screen;
   __DRIdrawable * const pdraw = GetDRIDrawable(dpy, drawable, & screen);
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs(dpy, screen);

   if ( (pdraw != NULL ) && (pdraw->queryFrameTracking != NULL)
        && __glXExtensionBitIsEnabled( psc, MESA_swap_frame_usage_bit ) ) {
      int64_t sbc, missedFrames;
      float   lastMissedUsage;

      status = pdraw->queryFrameTracking( dpy, pdraw->private, &sbc,
                                          &missedFrames, &lastMissedUsage,
                                          usage );
   }
#else
   (void) dpy;
   (void) drawable;
   (void) usage;
#endif
   return status;
}


GLint GLX_PREFIX(glXQueryFrameTrackingMESA)(Display *dpy, GLXDrawable drawable,
                                            int64_t *sbc, int64_t *missedFrames,
                                            GLfloat *lastMissedUsage)
{
   int   status = GLX_BAD_CONTEXT;
#ifdef GLX_DIRECT_RENDERING
   int screen;
   __DRIdrawable * const pdraw = GetDRIDrawable(dpy, drawable, & screen);
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs(dpy, screen);

   if ( (pdraw != NULL ) && (pdraw->queryFrameTracking != NULL)
        && __glXExtensionBitIsEnabled( psc, MESA_swap_frame_usage_bit ) ) {
      float   usage;

      status = pdraw->queryFrameTracking( dpy, pdraw->private, sbc,
                                          missedFrames, lastMissedUsage,
                                          & usage );
   }
#else
   (void) dpy;
   (void) drawable;
   (void) sbc;
   (void) missedFrames;
   (void) lastMissedUsage;
#endif
   return status;
}


/*
** GLX_SGI_video_sync
*/
int GLX_PREFIX(glXGetVideoSyncSGI)(unsigned int *count)
{
   /* FIXME: Looking at the GLX_SGI_video_sync spec in the extension registry,
    * FIXME: there should be a GLX encoding for this call.  I can find no
    * FIXME: documentation for the GLX encoding.
    */
#ifdef GLX_DIRECT_RENDERING
   GLXContext gc = __glXGetCurrentContext();


   if ( (gc != NULL) && gc->isDirect ) {
      __GLXscreenConfigs * const psc = GetGLXScreenConfigs( gc->currentDpy,
                                                            gc->screen );
      if ( __glXExtensionBitIsEnabled( psc, SGI_video_sync_bit )
           && psc->driScreen.private && psc->driScreen.getMSC) {
         int       ret;
         int64_t   temp;

         ret = psc->driScreen.getMSC( psc->driScreen.private, & temp );
         *count = (unsigned) temp;
         return (ret == 0) ? 0 : GLX_BAD_CONTEXT;
      }
   }
#else
    (void) count;
#endif
   return GLX_BAD_CONTEXT;
}

int GLX_PREFIX(glXWaitVideoSyncSGI)(int divisor, int remainder, unsigned int *count)
{
#ifdef GLX_DIRECT_RENDERING
   GLXContext gc = __glXGetCurrentContext();

   if ( divisor <= 0 || remainder < 0 )
     return GLX_BAD_VALUE;

   if ( (gc != NULL) && gc->isDirect ) {
      __GLXscreenConfigs * const psc = GetGLXScreenConfigs( gc->currentDpy,
                                                            gc->screen );
      if ( __glXExtensionBitIsEnabled( psc, SGI_video_sync_bit )
           && psc->driScreen.private ) {
         __DRIdrawable * const pdraw = 
             (*psc->driScreen.getDrawable)(gc->currentDpy,
                                           gc->currentDrawable,
                                           psc->driScreen.private);
         if ( (pdraw != NULL) && (pdraw->waitForMSC != NULL) ) {
            int       ret;
            int64_t   msc;
            int64_t   sbc;

            ret = (*pdraw->waitForMSC)( gc->currentDpy, pdraw->private,
                                        0, divisor, remainder,
                                        & msc, & sbc );
            *count = (unsigned) msc;
            return (ret == 0) ? 0 : GLX_BAD_CONTEXT;
         }
      }
   }
#else
   (void) count;
#endif
   return GLX_BAD_CONTEXT;
}


/*
** GLX_SGIS_video_source
*/
#if defined(_VL_H)

GLXVideoSourceSGIX GLX_PREFIX(glXCreateGLXVideoSourceSGIX)(Display *dpy, int screen, VLServer server, VLPath path, int nodeClass, VLNode drainNode)
{
   (void) dpy;
   (void) screen;
   (void) server;
   (void) path;
   (void) nodeClass;
   (void) drainNode;
   return 0;
}

void GLX_PREFIX(glXDestroyGLXVideoSourceSGIX)(Display *dpy, GLXVideoSourceSGIX src)
{
   (void) dpy;
   (void) src;
}

#endif


/*
** GLX_SGIX_fbconfig
** Many of these functions are aliased to GLX 1.3 entry points in the 
** GLX_functions table.
*/

GLX_ALIAS(int, glXGetFBConfigAttribSGIX,
          (Display *dpy, GLXFBConfigSGIX config, int attribute, int *value),
          (dpy, config, attribute, value),
          glXGetFBConfigAttrib)

GLX_ALIAS(GLXFBConfigSGIX *, glXChooseFBConfigSGIX,
          (Display *dpy, int screen, int *attrib_list, int *nelements),
          (dpy, screen, attrib_list, nelements),
          glXChooseFBConfig)

GLX_ALIAS(XVisualInfo *, glXGetVisualFromFBConfigSGIX,
          (Display * dpy, GLXFBConfigSGIX config),
          (dpy, config),
          glXGetVisualFromFBConfig)

GLXPixmap GLX_PREFIX(glXCreateGLXPixmapWithConfigSGIX)(Display *dpy, GLXFBConfigSGIX config, Pixmap pixmap)
{
    xGLXVendorPrivateWithReplyReq *vpreq;
    xGLXCreateGLXPixmapWithConfigSGIXReq *req;
    GLXPixmap xid = None;
    CARD8 opcode;
    const __GLcontextModes * const fbconfig = (__GLcontextModes *) config;
    __GLXscreenConfigs * psc;


    if ( (dpy == NULL) || (config == NULL) ) {
        return None;
    }

    psc = GetGLXScreenConfigs( dpy, fbconfig->screen );
    if ( (psc != NULL) 
         && __glXExtensionBitIsEnabled( psc, SGIX_fbconfig_bit ) ) {
        opcode = __glXSetupForCommand(dpy);
        if (!opcode) {
            return None;
        }

        /* Send the glXCreateGLXPixmapWithConfigSGIX request */
        LockDisplay(dpy);
        GetReqExtra(GLXVendorPrivateWithReply,
                    sz_xGLXCreateGLXPixmapWithConfigSGIXReq-sz_xGLXVendorPrivateWithReplyReq,vpreq);
        req = (xGLXCreateGLXPixmapWithConfigSGIXReq *)vpreq;
        req->reqType = opcode;
        req->glxCode = X_GLXVendorPrivateWithReply;
        req->vendorCode = X_GLXvop_CreateGLXPixmapWithConfigSGIX;
        req->screen = fbconfig->screen;
        req->fbconfig = fbconfig->fbconfigID;
        req->pixmap = pixmap;
        req->glxpixmap = xid = XAllocID(dpy);
        UnlockDisplay(dpy);
        SyncHandle();
    }

    return xid;
}

GLXContext GLX_PREFIX(glXCreateContextWithConfigSGIX)(Display *dpy, GLXFBConfigSGIX config, int renderType, GLXContext shareList, Bool allowDirect)
{
    GLXContext gc = NULL;
    const __GLcontextModes * const fbconfig = (__GLcontextModes *) config;
    __GLXscreenConfigs * psc;


    if ( (dpy == NULL) || (config == NULL) ) {
        return None;
    }

    psc = GetGLXScreenConfigs( dpy, fbconfig->screen );
    if ( (psc != NULL) 
         && __glXExtensionBitIsEnabled( psc, SGIX_fbconfig_bit ) ) {
        gc = CreateContext( dpy, NULL, (__GLcontextModes *) config, shareList,
                            allowDirect, None, False, renderType );
    }

    return gc;
}


GLXFBConfigSGIX GLX_PREFIX(glXGetFBConfigFromVisualSGIX)(Display *dpy, XVisualInfo *vis)
{
    __GLXdisplayPrivate *priv;
    __GLXscreenConfigs *psc;

    if ( (GetGLXPrivScreenConfig( dpy, vis->screen, & priv, & psc ) != Success)
         && __glXExtensionBitIsEnabled( psc, SGIX_fbconfig_bit )
         && (psc->configs->fbconfigID != GLX_DONT_CARE) ) {
        return (GLXFBConfigSGIX) _gl_context_modes_find_visual( psc->configs,
                                                                vis->visualid );
    }

    return NULL;
}


/*
** GLX_SGI_cushion
*/
void GLX_PREFIX(glXCushionSGI)(Display *dpy, Window win, float cushion)
{
   (void) dpy;
   (void) win;
   (void) cushion;
}


/*
** GLX_SGIX_video_resize
*/
int GLX_PREFIX(glXBindChannelToWindowSGIX)(Display *dpy, int screen, int channel , Window window)
{
   (void) dpy;
   (void) screen;
   (void) channel;
   (void) window;
   return 0;
}

int GLX_PREFIX(glXChannelRectSGIX)(Display *dpy, int screen, int channel, int x, int y, int w, int h)
{
   (void) dpy;
   (void) screen;
   (void) channel;
   (void) x;
   (void) y;
   (void) w;
   (void) h;
   return 0;
}

int GLX_PREFIX(glXQueryChannelRectSGIX)(Display *dpy, int screen, int channel, int *x, int *y, int *w, int *h)
{
   (void) dpy;
   (void) screen;
   (void) channel;
   (void) x;
   (void) y;
   (void) w;
   (void) h;
   return 0;
}

int GLX_PREFIX(glXQueryChannelDeltasSGIX)(Display *dpy, int screen, int channel, int *dx, int *dy, int *dw, int *dh)
{
   (void) dpy;
   (void) screen;
   (void) channel;
   (void) dx;
   (void) dy;
   (void) dw;
   (void) dh;
   return 0;
}

int GLX_PREFIX(glXChannelRectSyncSGIX)(Display *dpy, int screen, int channel, GLenum synctype)
{
   (void) dpy;
   (void) screen;
   (void) channel;
   (void) synctype;
   return 0;
}


#if defined(_DM_BUFFER_H_)

Bool GLX_PREFIX(glXAssociateDMPbufferSGIX)(Display *dpy, GLXPbufferSGIX pbuffer, DMparams *params, DMbuffer dmbuffer)
{
   (void) dpy;
   (void) pbuffer;
   (void) params;
   (void) dmbuffer;
   return False;
}

#endif


/*
** GLX_SGIX_swap_group
*/
void GLX_PREFIX(glXJoinSwapGroupSGIX)(Display *dpy, GLXDrawable drawable, GLXDrawable member)
{
   (void) dpy;
   (void) drawable;
   (void) member;
}


/*
** GLX_SGIX_swap_barrier
*/
void GLX_PREFIX(glXBindSwapBarrierSGIX)(Display *dpy, GLXDrawable drawable, int barrier)
{
   (void) dpy;
   (void) drawable;
   (void) barrier;
}

Bool GLX_PREFIX(glXQueryMaxSwapBarriersSGIX)(Display *dpy, int screen, int *max)
{
   (void) dpy;
   (void) screen;
   (void) max;
   return False;
}


/*
** GLX_SUN_get_transparent_index
*/
Status GLX_PREFIX(glXGetTransparentIndexSUN)(Display *dpy, Window overlay, Window underlay, long *pTransparent)
{
   (void) dpy;
   (void) overlay;
   (void) underlay;
   (void) pTransparent;
   return 0;
}


/*
** GLX_OML_sync_control
*/
Bool GLX_PREFIX(glXGetSyncValuesOML)(Display *dpy, GLXDrawable drawable,
                                     int64_t *ust, int64_t *msc, int64_t *sbc)
{
#ifdef GLX_DIRECT_RENDERING
    __GLXdisplayPrivate * const priv = __glXInitialize(dpy);

    if ( priv != NULL ) {
        int   i;
        __DRIdrawable * const pdraw = GetDRIDrawable( dpy, drawable, & i );
        __GLXscreenConfigs * const psc = &priv->screenConfigs[i];

        assert( (pdraw == NULL) || (i != -1) );
        return ( (pdraw && pdraw->getSBC && psc->driScreen.getMSC)
                 && __glXExtensionBitIsEnabled( psc, OML_sync_control_bit )
                 && ((*psc->driScreen.getMSC)( psc->driScreen.private, msc ) == 0)
                 && ((*pdraw->getSBC)( dpy, psc->driScreen.private, sbc ) == 0)
                 && (__glXGetUST( ust ) == 0) );
    }
#else
   (void) dpy;
   (void) drawable;
   (void) ust;
   (void) msc;
   (void) sbc;
#endif
   return False;
}


/**
 * Determine the refresh rate of the specified drawable and display.
 * 
 * \param dpy          Display whose refresh rate is to be determined.
 * \param drawable     Drawable whose refresh rate is to be determined.
 * \param numerator    Numerator of the refresh rate.
 * \param demoninator  Denominator of the refresh rate.
 * \return  If the refresh rate for the specified display and drawable could
 *          be calculated, True is returned.  Otherwise False is returned.
 * 
 * \note This function is implemented entirely client-side.  A lot of other
 *       functionality is required to export GLX_OML_sync_control, so on
 *       XFree86 this function can be called for direct-rendering contexts
 *       when GLX_OML_sync_control appears in the client extension string.
 */

Bool GLX_PREFIX(glXGetMscRateOML)(Display * dpy, GLXDrawable drawable,
                                  int32_t * numerator, int32_t * denominator)
{
#if defined( GLX_DIRECT_RENDERING ) && defined( XF86VIDMODE )
   __GLXdisplayPrivate * const priv = __glXInitialize(dpy);


   if ( priv != NULL ) {
      XF86VidModeModeLine   mode_line;
      int   dot_clock;
      int   screen_num;
      int   i;


      GetDRIDrawable( dpy, drawable, & screen_num );
      if ( (screen_num != -1)
           && XF86VidModeQueryVersion( dpy, & i, & i )
           && XF86VidModeGetModeLine( dpy, screen_num, & dot_clock,
                                      & mode_line ) ) {
         unsigned   n = dot_clock * 1000;
         unsigned   d = mode_line.vtotal * mode_line.htotal;

# define V_INTERLACE 0x010
# define V_DBLSCAN   0x020

         if ( (mode_line.flags & V_INTERLACE) ) {
            n *= 2;
         }
         else if ( (mode_line.flags & V_DBLSCAN) ) {
            d *= 2;
         }

         /* The OML_sync_control spec requires that if the refresh rate is a
          * whole number, that the returned numerator be equal to the refresh
          * rate and the denominator be 1.
          */

         if ( (n % d) == 0 ) {
            n /= d;
            d = 1;
         }
         else {
            static const unsigned f[] = { 13, 11, 7, 5, 3, 2, 0 };


            /* This is a poor man's way to reduce a fraction.  It's far from
             * perfect, but it will work well enough for this situation.
             */

            for ( i = 0 ; f[i] != 0 ; i++ ) {
               while ( ((n % f[i]) == 0) && ((d % f[i]) == 0) ) {
                  d /= f[i];
                  n /= f[i];
               }
            }
         }

         *numerator = n;
         *denominator = d;

         (void) drawable;
         return True;
      }
   }
#else
   (void) dpy;
   (void) drawable;
   (void) numerator;
   (void) denominator;
#endif
   return False;
}


int64_t GLX_PREFIX(glXSwapBuffersMscOML)(Display *dpy, GLXDrawable drawable,
                                         int64_t target_msc,
                                         int64_t divisor, int64_t remainder)
{
#ifdef GLX_DIRECT_RENDERING
   int screen;
   __DRIdrawable *pdraw = GetDRIDrawable( dpy, drawable, & screen );
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs( dpy, screen );

   /* The OML_sync_control spec says these should "generate a GLX_BAD_VALUE
    * error", but it also says "It [glXSwapBuffersMscOML] will return a value
    * of -1 if the function failed because of errors detected in the input
    * parameters"
    */
   if ( divisor < 0 || remainder < 0 || target_msc < 0 )
      return -1;
   if ( divisor > 0 && remainder >= divisor )
      return -1;

   if ( (pdraw != NULL) && (pdraw->swapBuffersMSC != NULL)
       && __glXExtensionBitIsEnabled( psc, OML_sync_control_bit ) ) {
      return (*pdraw->swapBuffersMSC)(dpy, pdraw->private, target_msc,
                                      divisor, remainder);
   }
#else
   (void) dpy;
   (void) drawable;
   (void) target_msc;
   (void) divisor;
   (void) remainder;
#endif
   return 0;
}


Bool GLX_PREFIX(glXWaitForMscOML)(Display * dpy, GLXDrawable drawable,
                                  int64_t target_msc,
                                  int64_t divisor, int64_t remainder,
                                  int64_t *ust, int64_t *msc, int64_t *sbc)
{
#ifdef GLX_DIRECT_RENDERING
   int screen;
   __DRIdrawable *pdraw = GetDRIDrawable( dpy, drawable, & screen );
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs( dpy, screen );
   int  ret;

   /* The OML_sync_control spec says these should "generate a GLX_BAD_VALUE
    * error", but the return type in the spec is Bool.
    */
   if ( divisor < 0 || remainder < 0 || target_msc < 0 )
      return False;
   if ( divisor > 0 && remainder >= divisor )
      return False;

   if ( (pdraw != NULL) && (pdraw->waitForMSC != NULL)
        && __glXExtensionBitIsEnabled( psc, OML_sync_control_bit ) ) {
      ret = (*pdraw->waitForMSC)( dpy, pdraw->private, target_msc,
                                  divisor, remainder, msc, sbc );

      /* __glXGetUST returns zero on success and non-zero on failure.
       * This function returns True on success and False on failure.
       */
      return ( (ret == 0) && (__glXGetUST( ust ) == 0) );
   }
#else
   (void) dpy;
   (void) drawable;
   (void) target_msc;
   (void) divisor;
   (void) remainder;
   (void) ust;
   (void) msc;
   (void) sbc;
#endif
   return False;
}


Bool GLX_PREFIX(glXWaitForSbcOML)(Display * dpy, GLXDrawable drawable,
                                  int64_t target_sbc,
                                  int64_t *ust, int64_t *msc, int64_t *sbc )
{
#ifdef GLX_DIRECT_RENDERING
   int screen;
   __DRIdrawable *pdraw = GetDRIDrawable( dpy, drawable, & screen );
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs( dpy, screen );
   int  ret;

   /* The OML_sync_control spec says this should "generate a GLX_BAD_VALUE
    * error", but the return type in the spec is Bool.
    */
   if ( target_sbc < 0 )
      return False;

   if ( (pdraw != NULL) && (pdraw->waitForSBC != NULL)
        && __glXExtensionBitIsEnabled( psc, OML_sync_control_bit )) {
      ret = (*pdraw->waitForSBC)( dpy, pdraw->private, target_sbc, msc, sbc );

      /* __glXGetUST returns zero on success and non-zero on failure.
       * This function returns True on success and False on failure.
       */
      return( (ret == 0) && (__glXGetUST( ust ) == 0) );
   }
#else
   (void) dpy;
   (void) drawable;
   (void) target_sbc;
   (void) ust;
   (void) msc;
   (void) sbc;
#endif
   return False;
}


/**
 * GLX_MESA_allocate_memory
 */
/*@{*/

void *GLX_PREFIX(glXAllocateMemoryMESA)(Display *dpy, int scrn,
                                        size_t size,
                                        float readFreq,
                                        float writeFreq,
                                        float priority)
{
#ifdef GLX_DIRECT_RENDERING
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs( dpy, scrn );

   if ( __glXExtensionBitIsEnabled( psc, MESA_allocate_memory_bit ) ) {
      if (psc && psc->driScreen.private && psc->driScreen.allocateMemory) {
         return (*psc->driScreen.allocateMemory)( dpy, scrn, size,
                                                  readFreq, writeFreq,
                                                  priority );
      }
   }
#else
   (void) dpy;
   (void) scrn;
   (void) size;
   (void) readFreq;
   (void) writeFreq;
   (void) priority;
#endif /* GLX_DIRECT_RENDERING */

   return NULL;
}


void GLX_PREFIX(glXFreeMemoryMESA)(Display *dpy, int scrn, void *pointer)
{
#ifdef GLX_DIRECT_RENDERING
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs( dpy, scrn );

   if ( __glXExtensionBitIsEnabled( psc, MESA_allocate_memory_bit ) ) {
      if (psc && psc->driScreen.private && psc->driScreen.freeMemory) {
         (*psc->driScreen.freeMemory)( dpy, scrn, pointer );
      }
   }
#else
   (void) dpy;
   (void) scrn;
   (void) pointer;
#endif /* GLX_DIRECT_RENDERING */
}


GLuint GLX_PREFIX(glXGetMemoryOffsetMESA)( Display *dpy, int scrn,
                                           const void *pointer )
{
#ifdef GLX_DIRECT_RENDERING
   __GLXscreenConfigs * const psc = GetGLXScreenConfigs( dpy, scrn );

   if ( __glXExtensionBitIsEnabled( psc, MESA_allocate_memory_bit ) ) {
      if (psc && psc->driScreen.private && psc->driScreen.memoryOffset) {
         return (*psc->driScreen.memoryOffset)( dpy, scrn, pointer );
      }
   }
#else
   (void) dpy;
   (void) scrn;
   (void) pointer;
#endif /* GLX_DIRECT_RENDERING */

   return ~0L;
}
/*@}*/


/**
 * Mesa extension stubs.  These will help reduce portability problems.
 */
/*@{*/

/**
 * Release all buffers associated with the specified GLX drawable.
 *
 * \todo
 * This function was intended for stand-alone Mesa.  The issue there is that
 * the library doesn't get any notification when a window is closed.  In
 * DRI there is a similar but slightly different issue.  When GLX 1.3 is
 * supported, there are 3 different functions to destroy a drawable.  It
 * should be possible to create GLX protocol (or have it determine which
 * protocol to use based on the type of the drawable) to have one function
 * do the work of 3.  For the direct-rendering case, this function could
 * just call the driver's \c __DRIdrawableRec::destroyDrawable function.
 * This would reduce the frequency with which \c __driGarbageCollectDrawables
 * would need to be used.  This really should be done as part of the new DRI
 * interface work.
 *
 * \sa http://oss.sgi.com/projects/ogl-sample/registry/MESA/release_buffers.txt
 *     __driGarbageCollectDrawables
 *     glXDestroyGLXPixmap
 *     glXDestroyPbuffer glXDestroyPixmap glXDestroyWindow
 *     glXDestroyGLXPbufferSGIX glXDestroyGLXVideoSourceSGIX
 */
Bool GLX_PREFIX(glXReleaseBuffersMESA)( Display *dpy, GLXDrawable d )
{
   (void) dpy;
   (void) d;
   return False;
}


GLXPixmap GLX_PREFIX(glXCreateGLXPixmapMESA)( Display *dpy,
                                              XVisualInfo *visual,
                                              Pixmap pixmap, Colormap cmap )
{
   (void) dpy;
   (void) visual;
   (void) pixmap;
   (void) cmap;
   return 0;
}


void GLX_PREFIX(glXCopySubBufferMESA)( Display *dpy, GLXDrawable drawable,
                                       int x, int y, int width, int height )
{
   (void) dpy;
   (void) drawable;
   (void) x;
   (void) y;
   (void) width;
   (void) height;
}


Bool GLX_PREFIX(glXSet3DfxModeMESA)( int mode )
{
   (void) mode;
   return GL_FALSE;
}
/*@}*/



/**
 * \c strdup is actually not a standard ANSI C or POSIX routine.
 * Irix will not define it if ANSI mode is in effect.
 * 
 * \sa strdup
 */
char *
__glXstrdup(const char *str)
{
   char *copy;
   copy = (char *) Xmalloc(strlen(str) + 1);
   if (!copy)
      return NULL;
   strcpy(copy, str);
   return copy;
}

/*
** glXGetProcAddress support
*/

struct name_address_pair {
   const char *Name;
   GLvoid *Address;
};

#define GLX_FUNCTION(f) { # f, (GLvoid *) f }
#define GLX_FUNCTION2(n,f) { # n, (GLvoid *) f }

static const struct name_address_pair GLX_functions[] = {
   /*** GLX_VERSION_1_0 ***/
   GLX_FUNCTION( glXChooseVisual ),
   GLX_FUNCTION( glXCopyContext ),
   GLX_FUNCTION( glXCreateContext ),
   GLX_FUNCTION( glXCreateGLXPixmap ),
   GLX_FUNCTION( glXDestroyContext ),
   GLX_FUNCTION( glXDestroyGLXPixmap ),
   GLX_FUNCTION( glXGetConfig ),
   GLX_FUNCTION( glXGetCurrentContext ),
   GLX_FUNCTION( glXGetCurrentDrawable ),
   GLX_FUNCTION( glXIsDirect ),
   GLX_FUNCTION( glXMakeCurrent ),
   GLX_FUNCTION( glXQueryExtension ),
   GLX_FUNCTION( glXQueryVersion ),
   GLX_FUNCTION( glXSwapBuffers ),
   GLX_FUNCTION( glXUseXFont ),
   GLX_FUNCTION( glXWaitGL ),
   GLX_FUNCTION( glXWaitX ),

   /*** GLX_VERSION_1_1 ***/
   GLX_FUNCTION( glXGetClientString ),
   GLX_FUNCTION( glXQueryExtensionsString ),
   GLX_FUNCTION( glXQueryServerString ),

   /*** GLX_VERSION_1_2 ***/
   GLX_FUNCTION( glXGetCurrentDisplay ),

   /*** GLX_VERSION_1_3 ***/
   GLX_FUNCTION( glXChooseFBConfig ),
   GLX_FUNCTION( glXCreateNewContext ),
   GLX_FUNCTION( glXCreatePbuffer ),
   GLX_FUNCTION( glXCreatePixmap ),
   GLX_FUNCTION( glXCreateWindow ),
   GLX_FUNCTION( glXDestroyPbuffer ),
   GLX_FUNCTION( glXDestroyPixmap ),
   GLX_FUNCTION( glXDestroyWindow ),
   GLX_FUNCTION( glXGetCurrentReadDrawable ),
   GLX_FUNCTION( glXGetFBConfigAttrib ),
   GLX_FUNCTION( glXGetFBConfigs ),
   GLX_FUNCTION( glXGetSelectedEvent ),
   GLX_FUNCTION( glXGetVisualFromFBConfig ),
   GLX_FUNCTION( glXMakeContextCurrent ),
   GLX_FUNCTION( glXQueryContext ),
   GLX_FUNCTION( glXQueryDrawable ),
   GLX_FUNCTION( glXSelectEvent ),

   /*** GLX_SGI_swap_control ***/
   GLX_FUNCTION( glXSwapIntervalSGI ),

   /*** GLX_SGI_video_sync ***/
   GLX_FUNCTION( glXGetVideoSyncSGI ),
   GLX_FUNCTION( glXWaitVideoSyncSGI ),

   /*** GLX_SGI_make_current_read ***/
   GLX_FUNCTION2( glXMakeCurrentReadSGI, glXMakeContextCurrent ),
   GLX_FUNCTION2( glXGetCurrentReadDrawableSGI, glXGetCurrentReadDrawable ),

   /*** GLX_SGIX_video_source ***/
#if defined(_VL_H)
   GLX_FUNCTION( glXCreateGLXVideoSourceSGIX ),
   GLX_FUNCTION( glXDestroyGLXVideoSourceSGIX ),
#endif

   /*** GLX_EXT_import_context ***/
   GLX_FUNCTION( glXFreeContextEXT ),
   GLX_FUNCTION( glXGetContextIDEXT ),
   GLX_FUNCTION2( glXGetCurrentDisplayEXT, glXGetCurrentDisplay ),
   GLX_FUNCTION( glXImportContextEXT ),
   GLX_FUNCTION2( glXQueryContextInfoEXT, glXQueryContext ),

   /*** GLX_SGIX_fbconfig ***/
   GLX_FUNCTION2( glXGetFBConfigAttribSGIX, glXGetFBConfigAttrib ),
   GLX_FUNCTION2( glXChooseFBConfigSGIX, glXChooseFBConfig ),
   GLX_FUNCTION( glXCreateGLXPixmapWithConfigSGIX ),
   GLX_FUNCTION( glXCreateContextWithConfigSGIX ),
   GLX_FUNCTION2( glXGetVisualFromFBConfigSGIX, glXGetVisualFromFBConfig ),
   GLX_FUNCTION( glXGetFBConfigFromVisualSGIX ),

   /*** GLX_SGIX_pbuffer ***/
   GLX_FUNCTION( glXCreateGLXPbufferSGIX ),
   GLX_FUNCTION( glXDestroyGLXPbufferSGIX ),
   GLX_FUNCTION( glXQueryGLXPbufferSGIX ),
   GLX_FUNCTION( glXSelectEventSGIX ),
   GLX_FUNCTION( glXGetSelectedEventSGIX ),

   /*** GLX_SGI_cushion ***/
   GLX_FUNCTION( glXCushionSGI ),

   /*** GLX_SGIX_video_resize ***/
   GLX_FUNCTION( glXBindChannelToWindowSGIX ),
   GLX_FUNCTION( glXChannelRectSGIX ),
   GLX_FUNCTION( glXQueryChannelRectSGIX ),
   GLX_FUNCTION( glXQueryChannelDeltasSGIX ),
   GLX_FUNCTION( glXChannelRectSyncSGIX ),

   /*** GLX_SGIX_dmbuffer **/
#if defined(_DM_BUFFER_H_)
   GLX_FUNCTION( glXAssociateDMPbufferSGIX ),
#endif

   /*** GLX_SGIX_swap_group ***/
   GLX_FUNCTION( glXJoinSwapGroupSGIX ),

   /*** GLX_SGIX_swap_barrier ***/
   GLX_FUNCTION( glXBindSwapBarrierSGIX ),
   GLX_FUNCTION( glXQueryMaxSwapBarriersSGIX ),

   /*** GLX_SUN_get_transparent_index ***/
   GLX_FUNCTION( glXGetTransparentIndexSUN ),

   /*** GLX_MESA_allocate_memory ***/
   GLX_FUNCTION( glXAllocateMemoryMESA ),
   GLX_FUNCTION( glXFreeMemoryMESA ),
   GLX_FUNCTION( glXGetMemoryOffsetMESA ),

   /*** GLX_MESA_copy_sub_buffer ***/
   GLX_FUNCTION( glXCopySubBufferMESA ),

   /*** GLX_MESA_pixmap_colormap ***/
   GLX_FUNCTION( glXCreateGLXPixmapMESA ),

   /*** GLX_MESA_release_buffers ***/
   GLX_FUNCTION( glXReleaseBuffersMESA ),

   /*** GLX_MESA_set_3dfx_mode ***/
   GLX_FUNCTION( glXSet3DfxModeMESA ),

   /*** GLX_MESA_swap_control ***/
   GLX_FUNCTION( glXSwapIntervalMESA ),
   GLX_FUNCTION( glXGetSwapIntervalMESA ),

   /*** GLX_MESA_swap_frame_usage ***/
   GLX_FUNCTION( glXBeginFrameTrackingMESA ),
   GLX_FUNCTION( glXEndFrameTrackingMESA ),
   GLX_FUNCTION( glXGetFrameUsageMESA ),
   GLX_FUNCTION( glXQueryFrameTrackingMESA ),

   /*** GLX_ARB_get_proc_address ***/
   GLX_FUNCTION( glXGetProcAddressARB ),

   /*** GLX 1.4 ***/
   GLX_FUNCTION2( glXGetProcAddress, glXGetProcAddressARB ),

   /*** GLX_OML_sync_control ***/
   GLX_FUNCTION( glXWaitForSbcOML ),
   GLX_FUNCTION( glXWaitForMscOML ),
   GLX_FUNCTION( glXSwapBuffersMscOML ),
   GLX_FUNCTION( glXGetMscRateOML ),
   GLX_FUNCTION( glXGetSyncValuesOML ),

#ifdef GLX_DIRECT_RENDERING
   /***
    *** Internal functions useful to DRI drivers
    *** With this, the DRI drivers shouldn't need dlopen()/dlsym() to
    *** access internal libGL functions which may or may not exist.
    ***/
   GLX_FUNCTION( __glXInitialize ),
   GLX_FUNCTION( __glXFindDRIScreen ),
   GLX_FUNCTION( __glXGetInternalVersion ),
   GLX_FUNCTION( __glXWindowExists ),
   GLX_FUNCTION2( __glXCreateContextWithConfig, XF86DRICreateContextWithConfig ),
   GLX_FUNCTION2( __glXGetDrawableInfo, XF86DRIGetDrawableInfo ),

   /*** DRI configuration ***/
   GLX_FUNCTION( glXGetScreenDriver ),
   GLX_FUNCTION( glXGetDriverConfig ),

   GLX_FUNCTION( __glXScrEnableExtension ),

   GLX_FUNCTION( __glXGetUST ),
    
   GLX_FUNCTION2( __glXCreateContextModes, _gl_context_modes_create ),
   GLX_FUNCTION2( __glXDestroyContextModes, _gl_context_modes_destroy ),
#endif

   { NULL, NULL }   /* end of list */
};


static const GLvoid *
get_glx_proc_address(const char *funcName)
{
   GLuint i;

   /* try static functions */
   for (i = 0; GLX_functions[i].Name; i++) {
      if (strcmp(GLX_functions[i].Name, funcName) == 0)
         return GLX_functions[i].Address;
   }

   return NULL;
}


#ifndef GLX_BUILT_IN_XMESA
/**
 * Get the address of a named GL function.  This is the pre-GLX 1.4 name for
 * \c glXGetProcAddress.
 *
 * \param procName  Name of a GL or GLX function.
 * \returns         A pointer to the named function
 *
 * \sa glXGetProcAddress
 */
void (*glXGetProcAddressARB(const GLubyte *procName))( void )
{
   typedef void (*gl_function)( void );
   gl_function f;


   /* Search the table of GLX and internal functions first.  If that
    * fails and the supplied name could be a valid core GL name, try
    * searching the core GL function table.  This check is done to prevent
    * DRI based drivers from searching the core GL function table for
    * internal API functions.
    */

   f = (gl_function) get_glx_proc_address((const char *) procName);
   if ( (f == NULL) && (procName[0] == 'g') && (procName[1] == 'l')
        && (procName[2] != 'X') ) {
      f = (gl_function) _glapi_get_proc_address((const char *) procName);
   }

   return f;
}

/**
 * Get the address of a named GL function.  This is the GLX 1.4 name for
 * \c glXGetProcAddressARB.
 *
 * \param procName  Name of a GL or GLX function.
 * \returns         A pointer to the named function
 *
 * \sa glXGetProcAddressARB
 */
void (*glXGetProcAddress(const GLubyte *procName))( void )
#if defined(__GNUC__) && !defined(GLX_ALIAS_UNSUPPORTED)
    __attribute__ ((alias ("glXGetProcAddressARB")));
#else
{
   return glXGetProcAddressARB(procName);
}
#endif /* __GNUC__ */
#endif /* GLX_BUILT_IN_XMESA */


#ifdef GLX_DIRECT_RENDERING
/**
 * Retrieves the verion of the internal libGL API in YYYYMMDD format.  This
 * might be used by the DRI drivers to determine how new libGL is at runtime.
 * Drivers should not call this function directly.  They should instead use
 * \c glXGetProcAddress to obtain a pointer to the function.
 * 
 * \returns An 8-digit decimal number representing the internal libGL API in
 *          YYYYMMDD format.
 * 
 * \sa glXGetProcAddress, PFNGLXGETINTERNALVERSIONPROC
 *
 * \since Internal API version 20021121.
 */
int __glXGetInternalVersion(void)
{
    /* History:
     * 20021121 - Initial version
     * 20021128 - Added __glXWindowExists() function
     * 20021207 - Added support for dynamic GLX extensions,
     *            GLX_SGI_swap_control, GLX_SGI_video_sync,
     *            GLX_OML_sync_control, and GLX_MESA_swap_control.
     *            Never officially released.  Do NOT test against
     *            this version.  Use 20030317 instead.
     * 20030317 - Added support GLX_SGIX_fbconfig,
     *            GLX_MESA_swap_frame_usage, GLX_OML_swap_method,
     *            GLX_{ARB,SGIS}_multisample, and
     *            GLX_SGIX_visual_select_group.
     * 20030606 - Added support for GLX_SGI_make_current_read.
     * 20030813 - Made support for dynamic extensions multi-head aware.
     * 20030818 - Added support for GLX_MESA_allocate_memory in place of the
     *            deprecated GLX_NV_vertex_array_range & GLX_MESA_agp_offset
     *            interfaces.
     * 20031201 - Added support for the first round of DRI interface changes.
     *            Do NOT test against this version!  It has binary
     *            compatibility bugs, use 20040317 instead.
     * 20040317 - Added the 'mode' field to __DRIcontextRec.
     * 20040415 - Added support for bindContext3 and unbindContext3.
     * 20040602 - Add __glXGetDrawableInfo.  I though that was there
     *            months ago. :(
     */
    return 20040602;
}



static Bool windowExistsFlag;

static int windowExistsErrorHandler(Display *dpy, XErrorEvent *xerr)
{
    if (xerr->error_code == BadWindow) {
        windowExistsFlag = GL_FALSE;
    }
    return 0;
}

/**
 * Determine if a window associated with a \c GLXDrawable exists on the
 * X-server.  This function is not used internally by libGL.  It is provided
 * as a utility function for DRI drivers.
 * Drivers should not call this function directly.  They should instead use
 * \c glXGetProcAddress to obtain a pointer to the function.
 *
 * \param dpy  Display associated with the drawable to be queried.
 * \param draw \c GLXDrawable to test.
 * 
 * \returns \c GL_TRUE if a window exists that is associated with \c draw,
 *          otherwise \c GL_FALSE is returned.
 * 
 * \warning This function is not currently thread-safe.
 *
 * \sa glXGetProcAddress
 *
 * \since Internal API version 20021128.
 */
static Bool __glXWindowExists(Display *dpy, GLXDrawable draw)
{
    XWindowAttributes xwa;
    int (*oldXErrorHandler)(Display *, XErrorEvent *);

    XSync(dpy, GL_FALSE);
    windowExistsFlag = GL_TRUE;
    oldXErrorHandler = XSetErrorHandler(windowExistsErrorHandler);
    XGetWindowAttributes(dpy, draw, &xwa); /* dummy request */
    XSetErrorHandler(oldXErrorHandler);
    return windowExistsFlag;
}


/**
 * Get the unadjusted system time (UST).  Currently, the UST is measured in
 * microseconds since Epoc.  The actual resolution of the UST may vary from
 * system to system, and the units may vary from release to release.
 * Drivers should not call this function directly.  They should instead use
 * \c glXGetProcAddress to obtain a pointer to the function.
 *
 * \param ust Location to store the 64-bit UST
 * \returns Zero on success or a negative errno value on failure.
 * 
 * \sa glXGetProcAddress, PFNGLXGETUSTPROC
 *
 * \since Internal API version 20030317.
 */
int __glXGetUST( int64_t * ust )
{
    struct timeval  tv;
    
    if ( ust == NULL ) {
        return -EFAULT;
    }

    if ( gettimeofday( & tv, NULL ) == 0 ) {
        ust[0] = (tv.tv_sec * 1000000) + tv.tv_usec;
        return 0;
    } else {
        return -errno;
    }
}
#endif /* GLX_DIRECT_RENDERING */