/*
 * Clutter.
 *
 * An OpenGL based 'interactive canvas' library.
 *
 * Authored By Matthew Allum  <mallum@openedhand.com>
 *
 * Copyright (C) 2006 OpenedHand
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/**
 * SECTION:clutter-feature
 * @short_description: functions to query available GL features ay runtime 
 *
 * Functions to query available GL features ay runtime 
 */

#include "config.h"

#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <errno.h>

#include <dlfcn.h>

#include "clutter-feature.h"
#include "clutter-main.h"
#include "clutter-private.h"
#include "clutter-debug.h"

typedef void (*FuncPtr) (void);
typedef int (*GLXGetVideoSyncProc)  (unsigned int *count);
typedef int (*GLXWaitVideoSyncProc) (int           divisor,
				     int          remainder,
				     unsigned int *count);
typedef FuncPtr (*GLXGetProcAddressProc) (const guint8 *procName);

typedef struct ClutterFeatureFuncs
{
  GLXGetVideoSyncProc  get_video_sync;
  GLXWaitVideoSyncProc wait_video_sync;

} ClutterFeatureFuncs;

typedef enum ClutterVBlankType
{
  CLUTTER_VBLANK_NONE = 0,
  CLUTTER_VBLANK_GLX,
  CLUTTER_VBLANK_DRI

} ClutterVBlankType;

typedef struct ClutterFeatures
{
  ClutterFeatureFlags flags;
  ClutterFeatureFuncs funcs;
  gint                dri_fd;
  ClutterVBlankType   vblank_type;

  guint               features_set : 1;
} ClutterFeatures;

static ClutterFeatures* __features = NULL;
G_LOCK_DEFINE_STATIC (__features);

/* #ifdef linux */
#define DRM_VBLANK_RELATIVE 0x1;

struct drm_wait_vblank_request {
    int           type;
    unsigned int  sequence;
    unsigned long signal;
};

struct drm_wait_vblank_reply {
    int          type;
    unsigned int sequence;
    long         tval_sec;
    long         tval_usec;
};

typedef union drm_wait_vblank {
    struct drm_wait_vblank_request request;
    struct drm_wait_vblank_reply reply;
} drm_wait_vblank_t;

#define DRM_IOCTL_BASE                  'd'
#define DRM_IOWR(nr,type)               _IOWR(DRM_IOCTL_BASE,nr,type)
#define DRM_IOCTL_WAIT_VBLANK           DRM_IOWR(0x3a, drm_wait_vblank_t)

static int drm_wait_vblank(int fd, drm_wait_vblank_t *vbl)
{
    int ret, rc;

    do 
      {
	ret = ioctl(fd, DRM_IOCTL_WAIT_VBLANK, vbl);
	vbl->request.type &= ~DRM_VBLANK_RELATIVE;
	rc = errno;
      } 
    while (ret && rc == EINTR);
    
    return rc;
}

/* #endif */


/* Note must be called after context created */
static gboolean 
check_gl_extension (const gchar *name,
                    const gchar *ext)
{
  gchar *end;
  gint name_len, n;

  if (name == NULL || ext == NULL)
    return FALSE;

  end = (gchar*)(ext + strlen(ext));

  name_len = strlen(name);

  while (ext < end) 
    {
      n = strcspn(ext, " ");

      if ((name_len == n) && (!strncmp(name, ext, n)))
	return TRUE;
      ext += (n + 1);
    }

  return FALSE;
}

static FuncPtr
get_proc_address (const gchar *name)
{
  static GLXGetProcAddressProc get_proc_func = NULL;
  static void                 *dlhand = NULL;

  if (get_proc_func == NULL && dlhand == NULL)
    {
      dlhand = dlopen (NULL, RTLD_LAZY);

      if (dlhand)
	{
	  dlerror ();

	  get_proc_func =
            (GLXGetProcAddressProc) dlsym (dlhand, "glXGetProcAddress");

	  if (dlerror () != NULL)
            {
              get_proc_func =
                (GLXGetProcAddressProc) dlsym (dlhand, "glXGetProcAddressARB");
            }

	  if (dlerror () != NULL)
	    {
	      get_proc_func = NULL;
	      g_warning ("failed to bind GLXGetProcAddress "
                         "or GLXGetProcAddressARB");
	    }
	}
    }

  if (get_proc_func)
    return get_proc_func ((unsigned char*) name);

  return NULL;
}


static gboolean
check_vblank_env (const char *name)
{
  const char *val;

  val = getenv("CLUTTER_VBLANK");

  if (val && !strcasecmp(val, name))
    return TRUE;

  return FALSE;
}

/* clutter_feature_init:
 * must be called with the static lock on __features held, to keep it
 * mt-safe.
 *
 * XXX - here we need a bit of weird machinery in place.  the features
 * are checked at run time, each time we try to access them - unless
 * we already checked them once.  unfortunately, we need an open
 * X display if we want to check them, so ideally we'd need to call
 * clutter_init() before checking for any feature.  the generator for
 * the api documentation, and more in general every tool relying on the
 * introspection API provided by GObject, may well not be able to call
 * clutter_init() (and neither they should be, as we might be running
 * them on a headless build box).  so, we need a way to get the features
 * without explicitely calling clutter_feature_init() inside clutter_init()
 * and we also need to have an open X display when we test for the features.
 * __features is dynamically allocated, and applications tend to badly
 * crash when trying to access __features components if we did not allocate
 * it; so when can't use a NULL check to know whether we already invoked
 * clutter_feature_init() once; hence, we must allocate it anyway, and have
 * a flag to let us know when the features have been set - that is when
 * clutter_feature_init() has been successfully completed with an open
 * X display.
 */
static void
clutter_feature_init (void)
{
  const gchar *gl_extensions, *glx_extensions;
  
  CLUTTER_NOTE (MISC, "checking features");

  if (!__features)
    {
      CLUTTER_NOTE (MISC, "allocating features data");

      __features = g_new0 (ClutterFeatures, 1);
      memset(&__features->funcs, 0, sizeof(ClutterFeatureFuncs));
      __features->features_set = FALSE; /* don't rely on zero-ing */
    }

  if (!clutter_xdisplay ())
    return;

  if (__features->features_set)
    return;

  gl_extensions = (const gchar*) glGetString (GL_EXTENSIONS);
  glx_extensions = glXQueryExtensionsString (clutter_xdisplay (),
                                             clutter_xscreen ());
  
  if (check_gl_extension ("GL_ARB_texture_rectangle", gl_extensions))
    __features->flags |= CLUTTER_FEATURE_TEXTURE_RECTANGLE;

  /* vblank */

  __features->vblank_type = CLUTTER_VBLANK_NONE;

  if (getenv("__GL_SYNC_TO_VBLANK") || check_vblank_env("none"))
    {
      CLUTTER_NOTE (MISC, "vblank sync: disabled at user request");
    }
  else
    {
      if (!check_vblank_env("dri") && 
	  check_gl_extension ("GLX_SGI_video_sync", glx_extensions))
	{
	  __features->funcs.get_video_sync = 
	     (GLXGetVideoSyncProc) get_proc_address ("glXGetVideoSyncSGI");

	  __features->funcs.wait_video_sync = 
	    (GLXWaitVideoSyncProc) get_proc_address ("glXWaitVideoSyncSGI");

	  if ((__features->funcs.get_video_sync != NULL) &&
	      (__features->funcs.wait_video_sync != NULL))
	    {
	      CLUTTER_NOTE (MISC, "vblank sync: using glx");
	      
              __features->vblank_type = CLUTTER_VBLANK_GLX;
	      __features->flags |= CLUTTER_FEATURE_SYNC_TO_VBLANK;
	    }
	}
	
      if (!(__features->flags & CLUTTER_FEATURE_SYNC_TO_VBLANK))
	{
	  __features->dri_fd = open("/dev/dri/card0", O_RDWR);
	  if (__features->dri_fd >= 0)
	    {
	      CLUTTER_NOTE (MISC, "vblank sync: using dri");

	      __features->vblank_type = CLUTTER_VBLANK_DRI;
	      __features->flags |= CLUTTER_FEATURE_SYNC_TO_VBLANK;
	    }
	}

      if (!(__features->flags & CLUTTER_FEATURE_SYNC_TO_VBLANK))
        {
          CLUTTER_NOTE (MISC,
                        "vblank sync: no use-able mechanism found");
        }
    }

  CLUTTER_NOTE (MISC, "features checked");

  __features->features_set = TRUE;
}

static void
clutter_feature_do_init (void)
{
  G_LOCK (__features);
  clutter_feature_init ();
  G_UNLOCK (__features);
}

/**
 * clutter_feature_available:
 * @feature: a #ClutterFeatureFlags
 *
 * Checks whether @feature is available.  @feature can be a logical
 * OR of #ClutterFeatureFlags.
 * 
 * Return value: %TRUE if a feature is available
 *
 * Since: 0.1.1
 */
gboolean
clutter_feature_available (ClutterFeatureFlags feature)
{
  clutter_feature_do_init ();

  return (__features->flags & feature);
}

/**
 * clutter_feature_get_all:
 *
 * Returns all the supported features.
 *
 * Return value: a logical OR of all the supported features.
 *
 * Since: 0.1.1
 */
ClutterFeatureFlags
clutter_feature_get_all (void)
{
  clutter_feature_do_init ();

  return __features->flags;
}

/**
 * clutter_feature_wait_for_vblank:
 *
 * FIXME
 *
 * Since: 0.2
 */
void
clutter_feature_wait_for_vblank (void)
{
  clutter_feature_do_init ();

  switch (__features->vblank_type)
    {
    case CLUTTER_VBLANK_GLX:
      {
	unsigned int retraceCount;
	__features->funcs.get_video_sync (&retraceCount);
	__features->funcs.wait_video_sync (2, 
					   (retraceCount + 1) % 2,
                                           &retraceCount); 
      }
      break;
    case CLUTTER_VBLANK_DRI:
      {
	drm_wait_vblank_t blank;
	blank.request.type     = DRM_VBLANK_RELATIVE;
	blank.request.sequence = 1;
	blank.request.signal   = 0;
	drm_wait_vblank (__features->dri_fd, &blank);
      }
      break;
    case CLUTTER_VBLANK_NONE:
    default:
      break;
    }
}