text: /*
   * Copyright 2008, 2010 George Sapountzis <gsapountzis@gmail.com>
   *
   * 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 and this permission notice 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
   * BRIAN PAUL 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.
   */
  
  /*
   * DRI software rasterizer
   *
   * This is the mesa swrast module packaged into a DRI driver structure.
   *
   * The front-buffer is allocated by the loader. The loader provides read/write
   * callbacks for access to the front-buffer. The driver uses a scratch row for
   * front-buffer rendering to avoid repeated calls to the loader.
   *
   * The back-buffer is allocated by the driver and is private.
   */
  
  #include "main/context.h"
  #include "main/extensions.h"
  #include "main/formats.h"
  #include "main/framebuffer.h"
  #include "main/imports.h"
  #include "main/renderbuffer.h"
  #include "swrast/swrast.h"
  #include "swrast/s_renderbuffer.h"
  #include "swrast_setup/swrast_setup.h"
  #include "tnl/tnl.h"
  #include "tnl/t_context.h"
  #include "tnl/t_pipeline.h"
  #include "vbo/vbo.h"
  #include "drivers/common/driverfuncs.h"
  #include "drivers/common/meta.h"
  #include "utils.h"
  
  #include "main/teximage.h"
  #include "main/texformat.h"
  #include "main/texstate.h"
  
  #include "swrast_priv.h"
  #include "swrast/s_context.h"
  
  
  /**
   * Screen and config-related functions
   */
  
  static void swrastSetTexBuffer2(__DRIcontext *pDRICtx, GLint target,
  				GLint texture_format, __DRIdrawable *dPriv)
  {
      struct dri_context *dri_ctx;
      int x, y, w, h;
      __DRIscreen *sPriv = dPriv->driScreenPriv;
      struct gl_texture_unit *texUnit;
      struct gl_texture_object *texObj;
      struct gl_texture_image *texImage;
      struct swrast_texture_image *swImage;
      uint32_t internalFormat;
      gl_format texFormat;
  
      dri_ctx = pDRICtx->driverPrivate;
  
      internalFormat = (texture_format == __DRI_TEXTURE_FORMAT_RGB ? 3 : 4);
  
      texUnit = _mesa_get_current_tex_unit(&dri_ctx->Base);
      texObj = _mesa_select_tex_object(&dri_ctx->Base, texUnit, target);
      texImage = _mesa_get_tex_image(&dri_ctx->Base, texObj, target, 0);
      swImage = swrast_texture_image(texImage);
  
      _mesa_lock_texture(&dri_ctx->Base, texObj);
  
      sPriv->swrast_loader->getDrawableInfo(dPriv, &x, &y, &w, &h, dPriv->loaderPrivate);
  
      if (texture_format == __DRI_TEXTURE_FORMAT_RGB)
  	texFormat = MESA_FORMAT_XRGB8888;
      else
  	texFormat = MESA_FORMAT_ARGB8888;
  
      _mesa_init_teximage_fields(&dri_ctx->Base, texImage,
  			       w, h, 1, 0, internalFormat, texFormat);
  
      sPriv->swrast_loader->getImage(dPriv, x, y, w, h, (char *)swImage->Buffer,
  				   dPriv->loaderPrivate);
  
      _mesa_unlock_texture(&dri_ctx->Base, texObj);
  }
  
  static void swrastSetTexBuffer(__DRIcontext *pDRICtx, GLint target,
  			       __DRIdrawable *dPriv)
  {
      swrastSetTexBuffer2(pDRICtx, target, __DRI_TEXTURE_FORMAT_RGBA, dPriv);
  }
  
  static const __DRItexBufferExtension swrastTexBufferExtension = {
      { __DRI_TEX_BUFFER, __DRI_TEX_BUFFER_VERSION },
      swrastSetTexBuffer,
      swrastSetTexBuffer2,
  };
  
  static const __DRIextension *dri_screen_extensions[] = {
      &swrastTexBufferExtension.base,
      NULL
  };
  
  static __DRIconfig **
  swrastFillInModes(__DRIscreen *psp,
  		  unsigned pixel_bits, unsigned depth_bits,
  		  unsigned stencil_bits, GLboolean have_back_buffer)
  {
      __DRIconfig **configs;
      unsigned depth_buffer_factor;
      unsigned back_buffer_factor;
      GLenum fb_format;
      GLenum fb_type;
  
      /* GLX_SWAP_COPY_OML is only supported because the Intel driver doesn't
       * support pageflipping at all.
       */
      static const GLenum back_buffer_modes[] = {
  	GLX_NONE, GLX_SWAP_UNDEFINED_OML
      };
  
      uint8_t depth_bits_array[4];
      uint8_t stencil_bits_array[4];
      uint8_t msaa_samples_array[1];
  
      (void) psp;
      (void) have_back_buffer;
  
      depth_bits_array[0] = 0;
      depth_bits_array[1] = 0;
      depth_bits_array[2] = depth_bits;
      depth_bits_array[3] = depth_bits;
  
      /* Just like with the accumulation buffer, always provide some modes
       * with a stencil buffer.
       */
      stencil_bits_array[0] = 0;
      stencil_bits_array[1] = (stencil_bits == 0) ? 8 : stencil_bits;
      stencil_bits_array[2] = 0;
      stencil_bits_array[3] = (stencil_bits == 0) ? 8 : stencil_bits;
  
      msaa_samples_array[0] = 0;
  
      depth_buffer_factor = 4;
      back_buffer_factor = 2;
  
      switch (pixel_bits) {
      case 8:
  	fb_format = GL_RGB;
  	fb_type = GL_UNSIGNED_BYTE_2_3_3_REV;
  	break;
      case 16:
  	fb_format = GL_RGB;
  	fb_type = GL_UNSIGNED_SHORT_5_6_5;
  	break;
      case 24:
  	fb_format = GL_BGR;
  	fb_type = GL_UNSIGNED_INT_8_8_8_8_REV;
  	break;
      case 32:
  	fb_format = GL_BGRA;
  	fb_type = GL_UNSIGNED_INT_8_8_8_8_REV;
  	break;
      default:
  	fprintf(stderr, "[%s:%u] bad depth %d\n", __func__, __LINE__,
  		pixel_bits);
  	return NULL;
      }
  
      configs = driCreateConfigs(fb_format, fb_type,
  			       depth_bits_array, stencil_bits_array,
  			       depth_buffer_factor, back_buffer_modes,
  			       back_buffer_factor, msaa_samples_array, 1,
  			       GL_TRUE);
      if (configs == NULL) {
  	fprintf(stderr, "[%s:%u] Error creating FBConfig!\n", __func__,
  		__LINE__);
  	return NULL;
      }
  
      return configs;
  }
  
  static const __DRIconfig **
  dri_init_screen(__DRIscreen * psp)
  {
      __DRIconfig **configs8, **configs16, **configs24, **configs32;
  
      TRACE;
  
      psp->extensions = dri_screen_extensions;
  
      configs8  = swrastFillInModes(psp,  8,  8, 0, 1);
      configs16 = swrastFillInModes(psp, 16, 16, 0, 1);
      configs24 = swrastFillInModes(psp, 24, 24, 8, 1);
      configs32 = swrastFillInModes(psp, 32, 24, 8, 1);
  
      configs16 = driConcatConfigs(configs8, configs16);
      configs24 = driConcatConfigs(configs16, configs24);
      configs32 = driConcatConfigs(configs24, configs32);
  
      return (const __DRIconfig **)configs32;
  }
  
  static void
  dri_destroy_screen(__DRIscreen * sPriv)
  {
      TRACE;
      (void) sPriv;
  }
  
  
  /**
   * Framebuffer and renderbuffer-related functions.
   */
  
  static GLuint
  choose_pixel_format(const struct gl_config *v)
  {
      int depth = v->rgbBits;
  
      if (depth == 32
  	&& v->redMask   == 0xff0000
  	&& v->greenMask == 0x00ff00
  	&& v->blueMask  == 0x0000ff)
  	return PF_A8R8G8B8;
      else if (depth == 24
  	     && v->redMask   == 0xff0000
  	     && v->greenMask == 0x00ff00
  	     && v->blueMask  == 0x0000ff)
  	return PF_X8R8G8B8;
      else if (depth == 16
  	     && v->redMask   == 0xf800
  	     && v->greenMask == 0x07e0
  	     && v->blueMask  == 0x001f)
  	return PF_R5G6B5;
      else if (depth == 8
  	     && v->redMask   == 0x07
  	     && v->greenMask == 0x38
  	     && v->blueMask  == 0xc0)
  	return PF_R3G3B2;
  
      _mesa_problem( NULL, "unexpected format in %s", __FUNCTION__ );
      return 0;
  }
  
  static void
  swrast_delete_renderbuffer(struct gl_renderbuffer *rb)
  {
      struct dri_swrast_renderbuffer *xrb = dri_swrast_renderbuffer(rb);
  
      TRACE;
  
      free(xrb->Base.Buffer);
      free(xrb);
  }
  
  /* see bytes_per_line in libGL */
  static INLINE int
  bytes_per_line(unsigned pitch_bits, unsigned mul)
  {
     unsigned mask = mul - 1;
  
     return ((pitch_bits + mask) & ~mask) / 8;
  }
  
  static GLboolean
  swrast_alloc_front_storage(struct gl_context *ctx, struct gl_renderbuffer *rb,
  			   GLenum internalFormat, GLuint width, GLuint height)
  {
      struct dri_swrast_renderbuffer *xrb = dri_swrast_renderbuffer(rb);
  
      TRACE;
  
      (void) ctx;
      (void) internalFormat;
  
      xrb->Base.Buffer = NULL;
      rb->Width = width;
      rb->Height = height;
      xrb->pitch = bytes_per_line(width * xrb->bpp, 32);
  
      return GL_TRUE;
  }
  
  static GLboolean
  swrast_alloc_back_storage(struct gl_context *ctx, struct gl_renderbuffer *rb,
  			  GLenum internalFormat, GLuint width, GLuint height)
  {
      struct dri_swrast_renderbuffer *xrb = dri_swrast_renderbuffer(rb);
  
      TRACE;
  
      free(xrb->Base.Buffer);
  
      swrast_alloc_front_storage(ctx, rb, internalFormat, width, height);
  
      xrb->Base.Buffer = malloc(height * xrb->pitch);
  
      return GL_TRUE;
  }
  
  static struct dri_swrast_renderbuffer *
  swrast_new_renderbuffer(const struct gl_config *visual, __DRIdrawable *dPriv,
  			GLboolean front)
  {
      struct dri_swrast_renderbuffer *xrb = calloc(1, sizeof *xrb);
      struct gl_renderbuffer *rb;
      GLuint pixel_format;
  
      TRACE;
  
      if (!xrb)
  	return NULL;
  
      rb = &xrb->Base.Base;
  
      _mesa_init_renderbuffer(rb, 0);
  
      pixel_format = choose_pixel_format(visual);
  
      xrb->dPriv = dPriv;
      xrb->Base.Base.Delete = swrast_delete_renderbuffer;
      if (front) {
          rb->AllocStorage = swrast_alloc_front_storage;
      }
      else {
  	rb->AllocStorage = swrast_alloc_back_storage;
      }
  
      switch (pixel_format) {
      case PF_A8R8G8B8:
  	rb->Format = MESA_FORMAT_ARGB8888;
  	rb->InternalFormat = GL_RGBA;
  	rb->_BaseFormat = GL_RGBA;
  	xrb->bpp = 32;
  	break;
      case PF_X8R8G8B8:
  	rb->Format = MESA_FORMAT_ARGB8888; /* XXX */
  	rb->InternalFormat = GL_RGB;
  	rb->_BaseFormat = GL_RGB;
  	xrb->bpp = 32;
  	break;
      case PF_R5G6B5:
  	rb->Format = MESA_FORMAT_RGB565;
  	rb->InternalFormat = GL_RGB;
  	rb->_BaseFormat = GL_RGB;
  	xrb->bpp = 16;
  	break;
      case PF_R3G3B2:
  	rb->Format = MESA_FORMAT_RGB332;
  	rb->InternalFormat = GL_RGB;
  	rb->_BaseFormat = GL_RGB;
  	xrb->bpp = 8;
  	break;
      default:
  	return NULL;
      }
  
      return xrb;
  }
  
  static void
  swrast_map_renderbuffer(struct gl_context *ctx,
  			struct gl_renderbuffer *rb,
  			GLuint x, GLuint y, GLuint w, GLuint h,
  			GLbitfield mode,
  			GLubyte **out_map,
  			GLint *out_stride)
  {
     struct dri_swrast_renderbuffer *xrb = dri_swrast_renderbuffer(rb);
     GLubyte *map = xrb->Base.Buffer;
     int cpp = _mesa_get_format_bytes(rb->Format);
     int stride = rb->Width * cpp;
  
     if (rb->AllocStorage == swrast_alloc_front_storage) {
        __DRIdrawable *dPriv = xrb->dPriv;
        __DRIscreen *sPriv = dPriv->driScreenPriv;
  
        xrb->map_mode = mode;
        xrb->map_x = x;
        xrb->map_y = y;
        xrb->map_w = w;
        xrb->map_h = h;
  
        stride = w * cpp;
        xrb->Base.Buffer = malloc(h * stride);
  
        sPriv->swrast_loader->getImage(dPriv, x, y, w, h,
  				     (char *) xrb->Base.Buffer,
  				     dPriv->loaderPrivate);
  
        *out_map = xrb->Base.Buffer;
        *out_stride = stride;
        return;
     }
  
     ASSERT(xrb->Base.Buffer);
  
     if (rb->AllocStorage == swrast_alloc_back_storage) {
        map += (rb->Height - 1) * stride;
        stride = -stride;
     }
  
     map += (GLsizei)y * stride;
     map += (GLsizei)x * cpp;
  
     *out_map = map;
     *out_stride = stride;
  }
  
  static void
  swrast_unmap_renderbuffer(struct gl_context *ctx,
  			  struct gl_renderbuffer *rb)
  {
     struct dri_swrast_renderbuffer *xrb = dri_swrast_renderbuffer(rb);
  
     if (rb->AllocStorage == swrast_alloc_front_storage) {
        __DRIdrawable *dPriv = xrb->dPriv;
        __DRIscreen *sPriv = dPriv->driScreenPriv;
  
        if (xrb->map_mode & GL_MAP_WRITE_BIT) {
  	 sPriv->swrast_loader->putImage(dPriv, __DRI_SWRAST_IMAGE_OP_DRAW,
  					xrb->map_x, xrb->map_y,
  					xrb->map_w, xrb->map_h,
  					(char *) xrb->Base.Buffer,
  					dPriv->loaderPrivate);
        }
  
        free(xrb->Base.Buffer);
        xrb->Base.Buffer = NULL;
     }
  }
  
  static GLboolean
  dri_create_buffer(__DRIscreen * sPriv,
  		  __DRIdrawable * dPriv,
  		  const struct gl_config * visual, GLboolean isPixmap)
  {
      struct dri_drawable *drawable = NULL;
      struct gl_framebuffer *fb;
      struct dri_swrast_renderbuffer *frontrb, *backrb;
  
      TRACE;
  
      (void) sPriv;
      (void) isPixmap;
  
      drawable = CALLOC_STRUCT(dri_drawable);
      if (drawable == NULL)
  	goto drawable_fail;
  
      dPriv->driverPrivate = drawable;
      drawable->dPriv = dPriv;
  
      drawable->row = malloc(MAX_WIDTH * 4);
      if (drawable->row == NULL)
  	goto drawable_fail;
  
      fb = &drawable->Base;
  
      /* basic framebuffer setup */
      _mesa_initialize_window_framebuffer(fb, visual);
  
      /* add front renderbuffer */
      frontrb = swrast_new_renderbuffer(visual, dPriv, GL_TRUE);
      _mesa_add_renderbuffer(fb, BUFFER_FRONT_LEFT, &frontrb->Base.Base);
  
      /* add back renderbuffer */
      if (visual->doubleBufferMode) {
  	backrb = swrast_new_renderbuffer(visual, dPriv, GL_FALSE);
  	_mesa_add_renderbuffer(fb, BUFFER_BACK_LEFT, &backrb->Base.Base);
      }
  
      /* add software renderbuffers */
      _swrast_add_soft_renderbuffers(fb,
                                     GL_FALSE, /* color */
                                     visual->haveDepthBuffer,
                                     visual->haveStencilBuffer,
                                     visual->haveAccumBuffer,
                                     GL_FALSE, /* alpha */
                                     GL_FALSE /* aux bufs */);
  
      return GL_TRUE;
  
  drawable_fail:
  
      if (drawable)
  	free(drawable->row);
  
      FREE(drawable);
  
      return GL_FALSE;
  }
  
  static void
  dri_destroy_buffer(__DRIdrawable * dPriv)
  {
      TRACE;
  
      if (dPriv) {
  	struct dri_drawable *drawable = dri_drawable(dPriv);
  	struct gl_framebuffer *fb;
  
  	free(drawable->row);
  
  	fb = &drawable->Base;
  
  	fb->DeletePending = GL_TRUE;
  	_mesa_reference_framebuffer(&fb, NULL);
      }
  }
  
  static void
  dri_swap_buffers(__DRIdrawable * dPriv)
  {
      __DRIscreen *sPriv = dPriv->driScreenPriv;
  
      GET_CURRENT_CONTEXT(ctx);
  
      struct dri_drawable *drawable = dri_drawable(dPriv);
      struct gl_framebuffer *fb;
      struct dri_swrast_renderbuffer *frontrb, *backrb;
  
      TRACE;
  
      fb = &drawable->Base;
  
      frontrb =
  	dri_swrast_renderbuffer(fb->Attachment[BUFFER_FRONT_LEFT].Renderbuffer);
      backrb =
  	dri_swrast_renderbuffer(fb->Attachment[BUFFER_BACK_LEFT].Renderbuffer);
  
      /* check for signle-buffered */
      if (backrb == NULL)
  	return;
  
      /* check if swapping currently bound buffer */
      if (ctx && ctx->DrawBuffer == fb) {
  	/* flush pending rendering */
  	_mesa_notifySwapBuffers(ctx);
      }
  
      sPriv->swrast_loader->putImage(dPriv, __DRI_SWRAST_IMAGE_OP_SWAP,
  				   0, 0,
  				   frontrb->Base.Base.Width,
  				   frontrb->Base.Base.Height,
  				   (char *) backrb->Base.Buffer,
  				   dPriv->loaderPrivate);
  }
  
  
  /**
   * General device driver functions.
   */
  
  static void
  get_window_size( struct gl_framebuffer *fb, GLsizei *w, GLsizei *h )
  {
      __DRIdrawable *dPriv = swrast_drawable(fb)->dPriv;
      __DRIscreen *sPriv = dPriv->driScreenPriv;
      int x, y;
  
      sPriv->swrast_loader->getDrawableInfo(dPriv,
  					  &x, &y, w, h,
  					  dPriv->loaderPrivate);
  }
  
  static void
  swrast_check_and_update_window_size( struct gl_context *ctx, struct gl_framebuffer *fb )
  {
      GLsizei width, height;
  
      get_window_size(fb, &width, &height);
      if (fb->Width != width || fb->Height != height) {
  	_mesa_resize_framebuffer(ctx, fb, width, height);
      }
  }
  
  static const GLubyte *
  get_string(struct gl_context *ctx, GLenum pname)
  {
      (void) ctx;
      switch (pname) {
  	case GL_VENDOR:
  	    return (const GLubyte *) "Mesa Project";
  	case GL_RENDERER:
  	    return (const GLubyte *) "Software Rasterizer";
  	default:
  	    return NULL;
      }
  }
  
  static void
  update_state( struct gl_context *ctx, GLuint new_state )
  {
      /* not much to do here - pass it on */
      _swrast_InvalidateState( ctx, new_state );
      _swsetup_InvalidateState( ctx, new_state );
      _vbo_InvalidateState( ctx, new_state );
      _tnl_InvalidateState( ctx, new_state );
  }
  
  static void
  viewport(struct gl_context *ctx, GLint x, GLint y, GLsizei w, GLsizei h)
  {
      struct gl_framebuffer *draw = ctx->WinSysDrawBuffer;
      struct gl_framebuffer *read = ctx->WinSysReadBuffer;
  
      (void) x;
      (void) y;
      (void) w;
      (void) h;
      swrast_check_and_update_window_size(ctx, draw);
      swrast_check_and_update_window_size(ctx, read);
  }
  
  static gl_format swrastChooseTextureFormat(struct gl_context * ctx,
  					   GLint internalFormat,
  					   GLenum format,
  					   GLenum type)
  {
      if (internalFormat == GL_RGB)
  	return MESA_FORMAT_XRGB8888;
      return _mesa_choose_tex_format(ctx, internalFormat, format, type);
  }
  
  static void
  swrast_init_driver_functions(struct dd_function_table *driver)
  {
      driver->GetString = get_string;
      driver->UpdateState = update_state;
      driver->GetBufferSize = NULL;
      driver->Viewport = viewport;
      driver->ChooseTextureFormat = swrastChooseTextureFormat;
      driver->MapRenderbuffer = swrast_map_renderbuffer;
      driver->UnmapRenderbuffer = swrast_unmap_renderbuffer;
  }
  
  static const char *es2_extensions[] = {
     /* Used by mesa internally (cf all_mesa_extensions in ../common/utils.c) */
     "GL_ARB_transpose_matrix",
     "GL_ARB_window_pos",
     "GL_EXT_blend_func_separate",
     "GL_EXT_compiled_vertex_array",
     "GL_EXT_framebuffer_blit",
     "GL_IBM_multimode_draw_arrays",
     "GL_MESA_window_pos",
     "GL_NV_vertex_program",
  
     /* Required by GLES2 */
     "GL_ARB_fragment_program",
     "GL_ARB_fragment_shader",
     "GL_ARB_shader_objects",
     "GL_ARB_texture_cube_map",
     "GL_ARB_texture_non_power_of_two",
     "GL_ARB_vertex_shader",
     "GL_EXT_blend_color",
     "GL_EXT_blend_equation_separate",
     "GL_EXT_blend_minmax",
  
     /* Optional GLES2 */
     "GL_ARB_framebuffer_object",
     "GL_EXT_texture_filter_anisotropic",
     "GL_ARB_depth_texture",
     "GL_EXT_packed_depth_stencil",
     "GL_EXT_framebuffer_object",
     NULL,
  };
  
  static void
  InitExtensionsES2(struct gl_context *ctx)
  {
     int i;
  
     for (i = 0; es2_extensions[i]; i++)
        _mesa_enable_extension(ctx, es2_extensions[i]);
  }
  
  /**
   * Context-related functions.
   */
  
  static GLboolean
  dri_create_context(gl_api api,
  		   const struct gl_config * visual,
  		   __DRIcontext * cPriv,
  		   unsigned major_version,
  		   unsigned minor_version,
  		   uint32_t flags,
  		   unsigned *error,
  		   void *sharedContextPrivate)
  {
      struct dri_context *ctx = NULL;
      struct dri_context *share = (struct dri_context *)sharedContextPrivate;
      struct gl_context *mesaCtx = NULL;
      struct gl_context *sharedCtx = NULL;
      struct dd_function_table functions;
  
      TRACE;
  
      /* Flag filtering is handled in dri2CreateContextAttribs.
       */
      (void) flags;
  
      if (api == API_OPENGL
  	&& (major_version > 2
  	    || (major_version == 2 && minor_version > 1))) {
         *error = __DRI_CTX_ERROR_BAD_VERSION;
         goto context_fail;
      }
  
      ctx = CALLOC_STRUCT(dri_context);
      if (ctx == NULL) {
  	*error = __DRI_CTX_ERROR_NO_MEMORY;
  	goto context_fail;
      }
  
      cPriv->driverPrivate = ctx;
      ctx->cPriv = cPriv;
  
      /* build table of device driver functions */
      _mesa_init_driver_functions(&functions);
      swrast_init_driver_functions(&functions);
  
      if (share) {
  	sharedCtx = &share->Base;
      }
  
      mesaCtx = &ctx->Base;
  
      /* basic context setup */
      if (!_mesa_initialize_context(mesaCtx, api, visual, sharedCtx, &functions, (void *) cPriv)) {
  	*error = __DRI_CTX_ERROR_NO_MEMORY;
  	goto context_fail;
      }
  
      /* do bounds checking to prevent segfaults and server crashes! */
      mesaCtx->Const.CheckArrayBounds = GL_TRUE;
  
      /* create module contexts */
      _swrast_CreateContext( mesaCtx );
      _vbo_CreateContext( mesaCtx );
      _tnl_CreateContext( mesaCtx );
      _swsetup_CreateContext( mesaCtx );
      _swsetup_Wakeup( mesaCtx );
  
      /* use default TCL pipeline */
      {
         TNLcontext *tnl = TNL_CONTEXT(mesaCtx);
         tnl->Driver.RunPipeline = _tnl_run_pipeline;
      }
  
      _mesa_meta_init(mesaCtx);
      _mesa_enable_sw_extensions(mesaCtx);
  
      switch (api) {
      case API_OPENGL:
          _mesa_enable_1_3_extensions(mesaCtx);
          _mesa_enable_1_4_extensions(mesaCtx);
          _mesa_enable_1_5_extensions(mesaCtx);
          _mesa_enable_2_0_extensions(mesaCtx);
          _mesa_enable_2_1_extensions(mesaCtx);
          break;
      case API_OPENGLES:
          _mesa_enable_1_3_extensions(mesaCtx);
          _mesa_enable_1_4_extensions(mesaCtx);
          _mesa_enable_1_5_extensions(mesaCtx);
  
          break;
      case API_OPENGLES2:
          InitExtensionsES2( mesaCtx);
          break;
      }
  
      *error = __DRI_CTX_ERROR_SUCCESS;
      return GL_TRUE;
  
  context_fail:
  
      FREE(ctx);
  
      return GL_FALSE;
  }
  
  static void
  dri_destroy_context(__DRIcontext * cPriv)
  {
      TRACE;
  
      if (cPriv) {
  	struct dri_context *ctx = dri_context(cPriv);
  	struct gl_context *mesaCtx;
  
  	mesaCtx = &ctx->Base;
  
          _mesa_meta_free(mesaCtx);
  	_swsetup_DestroyContext( mesaCtx );
  	_swrast_DestroyContext( mesaCtx );
  	_tnl_DestroyContext( mesaCtx );
  	_vbo_DestroyContext( mesaCtx );
  	_mesa_destroy_context( mesaCtx );
      }
  }
  
  static GLboolean
  dri_make_current(__DRIcontext * cPriv,
  		 __DRIdrawable * driDrawPriv,
  		 __DRIdrawable * driReadPriv)
  {
      struct gl_context *mesaCtx;
      struct gl_framebuffer *mesaDraw;
      struct gl_framebuffer *mesaRead;
      TRACE;
  
      if (cPriv) {
  	struct dri_context *ctx = dri_context(cPriv);
  	struct dri_drawable *draw;
  	struct dri_drawable *read;
  
  	if (!driDrawPriv || !driReadPriv)
  	    return GL_FALSE;
  
  	draw = dri_drawable(driDrawPriv);
  	read = dri_drawable(driReadPriv);
  	mesaCtx = &ctx->Base;
  	mesaDraw = &draw->Base;
  	mesaRead = &read->Base;
  
  	/* check for same context and buffer */
  	if (mesaCtx == _mesa_get_current_context()
  	    && mesaCtx->DrawBuffer == mesaDraw
  	    && mesaCtx->ReadBuffer == mesaRead) {
  	    return GL_TRUE;
  	}
  
  	_glapi_check_multithread();
  
  	swrast_check_and_update_window_size(mesaCtx, mesaDraw);
  	if (mesaRead != mesaDraw)
  	    swrast_check_and_update_window_size(mesaCtx, mesaRead);
  
  	_mesa_make_current( mesaCtx,
  			    mesaDraw,
  			    mesaRead );
      }
      else {
  	/* unbind */
  	_mesa_make_current( NULL, NULL, NULL );
      }
  
      return GL_TRUE;
  }
  
  static GLboolean
  dri_unbind_context(__DRIcontext * cPriv)
  {
      TRACE;
      (void) cPriv;
  
      /* Unset current context and dispath table */
      _mesa_make_current(NULL, NULL, NULL);
  
      return GL_TRUE;
  }
  
  
  const struct __DriverAPIRec driDriverAPI = {
      .InitScreen = dri_init_screen,
      .DestroyScreen = dri_destroy_screen,
      .CreateContext = dri_create_context,
      .DestroyContext = dri_destroy_context,
      .CreateBuffer = dri_create_buffer,
      .DestroyBuffer = dri_destroy_buffer,
      .SwapBuffers = dri_swap_buffers,
      .MakeCurrent = dri_make_current,
      .UnbindContext = dri_unbind_context,
  };
  
  /* This is the table of extensions that the loader will dlsym() for. */
  PUBLIC const __DRIextension *__driDriverExtensions[] = {
      &driCoreExtension.base,
      &driSWRastExtension.base,
      NULL
  };
  