/*
 * SGI FREE SOFTWARE LICENSE B (Version 2.0, Sept. 18, 2008)
 * Copyright (C) 1991-2000 Silicon Graphics, Inc. All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice including the dates of first publication and
 * either this permission notice or a reference to
 * http://oss.sgi.com/projects/FreeB/
 * shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * SILICON GRAPHICS, INC. BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
 * OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * Except as contained in this notice, the name of Silicon Graphics, Inc.
 * shall not be used in advertising or otherwise to promote the sale, use or
 * other dealings in this Software without prior written authorization from
 * Silicon Graphics, Inc.
 */

/**
 * \file glxcurrent.c
 * Client-side GLX interface for current context management.
 */

#include <pthread.h>

#include "glxclient.h"
#include "glapi.h"
#include "glx_error.h"

/*
** We setup some dummy structures here so that the API can be used
** even if no context is current.
*/

static GLubyte dummyBuffer[__GLX_BUFFER_LIMIT_SIZE];
static struct glx_context_vtable dummyVtable;
/*
** Dummy context used by small commands when there is no current context.
** All the
** gl and glx entry points are designed to operate as nop's when using
** the dummy context structure.
*/
struct glx_context dummyContext = {
   &dummyBuffer[0],
   &dummyBuffer[0],
   &dummyBuffer[0],
   &dummyBuffer[__GLX_BUFFER_LIMIT_SIZE],
   sizeof(dummyBuffer),
   &dummyVtable
};

/*
 * Current context management and locking
 */

_X_HIDDEN pthread_mutex_t __glXmutex = PTHREAD_MUTEX_INITIALIZER;

/**
 * Per-thread GLX context pointer.
 *
 * \c __glXSetCurrentContext is written is such a way that this pointer can
 * \b never be \c NULL.  This is important!  Because of this
 * \c __glXGetCurrentContext can be implemented as trivial macro.
 */
__THREAD_INITIAL_EXEC void *__glX_tls_Context = &dummyContext;

_X_HIDDEN void
__glXSetCurrentContext(struct glx_context * c)
{
   __glX_tls_Context = (c != NULL) ? c : &dummyContext;
}

_X_HIDDEN void
__glXSetCurrentContextNull(void)
{
   __glXSetCurrentContext(&dummyContext);
#if defined(GLX_DIRECT_RENDERING)
   _glapi_set_dispatch(NULL);   /* no-op functions */
   _glapi_set_context(NULL);
#endif
}

_GLX_PUBLIC GLXContext
glXGetCurrentContext(void)
{
   struct glx_context *cx = __glXGetCurrentContext();

   if (cx == &dummyContext) {
      return NULL;
   }
   else {
      return (GLXContext) cx;
   }
}

_GLX_PUBLIC GLXDrawable
glXGetCurrentDrawable(void)
{
   struct glx_context *gc = __glXGetCurrentContext();
   return gc->currentDrawable;
}

/**
 * Make a particular context current.
 *
 * \note This is in this file so that it can access dummyContext.
 */
static Bool
MakeContextCurrent(Display * dpy, GLXDrawable draw,
                   GLXDrawable read, GLXContext gc_user,
                   int opcode)
{
   struct glx_context *gc = (struct glx_context *) gc_user;
   struct glx_context *oldGC = __glXGetCurrentContext();

   /* Make sure that the new context has a nonzero ID.  In the request,
    * a zero context ID is used only to mean that we bind to no current
    * context.
    */
   if ((gc != NULL) && (gc->xid == None)) {
      return GL_FALSE;
   }

   __glXLock();
   if (oldGC == gc &&
       gc->currentDrawable == draw && gc->currentReadable == read) {
      __glXUnlock();
      return True;
   }

   /* can't have only one be 0 */
   if (!!draw != !!read) {
      __glXUnlock();
      __glXSendError(dpy, BadMatch, None, opcode, True);
      return False;
   }

   if (oldGC != &dummyContext) {
      oldGC->vtable->unbind(oldGC, gc);
      oldGC->currentDpy = NULL;
   }

   if (gc) {
      /* Attempt to bind the context.  We do this before mucking with
       * gc and __glXSetCurrentContext to properly handle our state in
       * case of an error.
       *
       * If an error occurs, set the Null context since we've already
       * blown away our old context.  The caller is responsible for
       * figuring out how to handle setting a valid context.
       */
      if (gc->vtable->bind(gc, oldGC, draw, read) != Success) {
         __glXSetCurrentContextNull();
         __glXUnlock();
         __glXSendError(dpy, GLXBadContext, None, opcode, False);
         return GL_FALSE;
      }

      gc->currentDpy = dpy;
      gc->currentDrawable = draw;
      gc->currentReadable = read;
      __glXSetCurrentContext(gc);
   } else {
      __glXSetCurrentContextNull();
   }

   if (oldGC->currentDpy == NULL && oldGC != &dummyContext && oldGC->xid == None) {
      /* We are switching away from a context that was
       * previously destroyed, so we need to free the memory
       * for the old handle. */
      oldGC->vtable->destroy(oldGC);
   }

   __glXUnlock();

   return GL_TRUE;
}

_GLX_PUBLIC Bool
glXMakeCurrent(Display * dpy, GLXDrawable draw, GLXContext gc)
{
   return MakeContextCurrent(dpy, draw, draw, gc, X_GLXMakeCurrent);
}

_GLX_PUBLIC Bool
glXMakeContextCurrent(Display *dpy, GLXDrawable d, GLXDrawable r,
                      GLXContext ctx)
{
   return MakeContextCurrent(dpy, d, r, ctx, X_GLXMakeContextCurrent);
}

_GLX_PUBLIC Bool
glXMakeCurrentReadSGI(Display *dpy, GLXDrawable d, GLXDrawable r,
                      GLXContext ctx)
{
   return MakeContextCurrent(dpy, d, r, ctx, X_GLXvop_MakeCurrentReadSGI);
}