context.c

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   ctx->Const.FragmentProgram.MaxUniformComponents = 4 * MAX_UNIFORMS;
   init_natives(&ctx->Const.FragmentProgram);
#endif
   ctx->Const.MaxProgramMatrices = MAX_PROGRAM_MATRICES;
   ctx->Const.MaxProgramMatrixStackDepth = MAX_PROGRAM_MATRIX_STACK_DEPTH;

   /* CheckArrayBounds is overriden by drivers/x11 for X server */
   ctx->Const.CheckArrayBounds = GL_FALSE;

   /* GL_ARB_draw_buffers */
   ctx->Const.MaxDrawBuffers = MAX_DRAW_BUFFERS;

   /* GL_OES_read_format */
   ctx->Const.ColorReadFormat = GL_RGBA;
   ctx->Const.ColorReadType = GL_UNSIGNED_BYTE;

#if FEATURE_EXT_framebuffer_object
   ctx->Const.MaxColorAttachments = MAX_COLOR_ATTACHMENTS;
   ctx->Const.MaxRenderbufferSize = MAX_WIDTH;
#endif

#if FEATURE_ARB_vertex_shader
   ctx->Const.MaxVertexTextureImageUnits = MAX_VERTEX_TEXTURE_IMAGE_UNITS;
   ctx->Const.MaxVarying = MAX_VARYING;
#endif

   /* sanity checks */
   ASSERT(ctx->Const.MaxTextureUnits == MIN2(ctx->Const.MaxTextureImageUnits,
                                             ctx->Const.MaxTextureCoordUnits));
   ASSERT(ctx->Const.FragmentProgram.MaxLocalParams <= MAX_PROGRAM_LOCAL_PARAMS);
   ASSERT(ctx->Const.VertexProgram.MaxLocalParams <= MAX_PROGRAM_LOCAL_PARAMS);

   ASSERT(MAX_NV_FRAGMENT_PROGRAM_TEMPS <= MAX_PROGRAM_TEMPS);
   ASSERT(MAX_NV_VERTEX_PROGRAM_TEMPS <= MAX_PROGRAM_TEMPS);
   ASSERT(MAX_NV_VERTEX_PROGRAM_INPUTS <= VERT_ATTRIB_MAX);
   ASSERT(MAX_NV_VERTEX_PROGRAM_OUTPUTS <= VERT_RESULT_MAX);
}


/**
 * Do some sanity checks on the limits/constants for the given context.
 * Only called the first time a context is bound.
 */
static void
check_context_limits(GLcontext *ctx)
{
   /* Many context limits/constants are limited by the size of
    * internal arrays.
    */
   assert(ctx->Const.MaxTextureImageUnits <= MAX_TEXTURE_IMAGE_UNITS);
   assert(ctx->Const.MaxTextureCoordUnits <= MAX_TEXTURE_COORD_UNITS);
   assert(ctx->Const.MaxTextureUnits <= MAX_TEXTURE_IMAGE_UNITS);
   assert(ctx->Const.MaxTextureUnits <= MAX_TEXTURE_COORD_UNITS);

   assert(ctx->Const.MaxViewportWidth <= MAX_WIDTH);
   assert(ctx->Const.MaxViewportHeight <= MAX_WIDTH);

   /* make sure largest texture image is <= MAX_WIDTH in size */
   assert((1 << (ctx->Const.MaxTextureLevels -1 )) <= MAX_WIDTH);
   assert((1 << (ctx->Const.MaxCubeTextureLevels -1 )) <= MAX_WIDTH);
   assert((1 << (ctx->Const.Max3DTextureLevels -1 )) <= MAX_WIDTH);

   assert(ctx->Const.MaxDrawBuffers <= MAX_DRAW_BUFFERS);

   /* XXX probably add more tests */
}


/**
 * Initialize the attribute groups in a GL context.
 *
 * \param ctx GL context.
 *
 * Initializes all the attributes, calling the respective <tt>init*</tt>
 * functions for the more complex data structures.
 */
static GLboolean
init_attrib_groups(GLcontext *ctx)
{
   assert(ctx);

   /* Constants */
   _mesa_init_constants( ctx );

   /* Extensions */
   _mesa_init_extensions( ctx );

   /* Attribute Groups */
   _mesa_init_accum( ctx );
   _mesa_init_attrib( ctx );
   _mesa_init_buffer_objects( ctx );
   _mesa_init_color( ctx );
   _mesa_init_colortables( ctx );
   _mesa_init_current( ctx );
   _mesa_init_depth( ctx );
   _mesa_init_debug( ctx );
   _mesa_init_display_list( ctx );
   _mesa_init_eval( ctx );
   _mesa_init_fbobjects( ctx );
   _mesa_init_feedback( ctx );
   _mesa_init_fog( ctx );
   _mesa_init_histogram( ctx );
   _mesa_init_hint( ctx );
   _mesa_init_line( ctx );
   _mesa_init_lighting( ctx );
   _mesa_init_matrix( ctx );
   _mesa_init_multisample( ctx );
   _mesa_init_pixel( ctx );
   _mesa_init_point( ctx );
   _mesa_init_polygon( ctx );
   _mesa_init_program( ctx );
   _mesa_init_query( ctx );
   _mesa_init_rastpos( ctx );
   _mesa_init_scissor( ctx );
   _mesa_init_shader_state( ctx );
   _mesa_init_stencil( ctx );
   _mesa_init_transform( ctx );
   _mesa_init_varray( ctx );
   _mesa_init_viewport( ctx );

   if (!_mesa_init_texture( ctx ))
      return GL_FALSE;

   _mesa_init_texture_s3tc( ctx );
   _mesa_init_texture_fxt1( ctx );

   /* Miscellaneous */
   ctx->NewState = _NEW_ALL;
   ctx->ErrorValue = (GLenum) GL_NO_ERROR;

   return GL_TRUE;
}


/**
 * Update default objects in a GL context with respect to shared state.
 *
 * \param ctx GL context.
 *
 * Removes references to old default objects, (texture objects, program
 * objects, etc.) and changes to reference those from the current shared
 * state.
 */
static GLboolean
update_default_objects(GLcontext *ctx)
{
   assert(ctx);

   _mesa_update_default_objects_program(ctx);
   _mesa_update_default_objects_texture(ctx);
   _mesa_update_default_objects_buffer_objects(ctx);

   return GL_TRUE;
}


/**
 * This is the default function we plug into all dispatch table slots
 * This helps prevents a segfault when someone calls a GL function without
 * first checking if the extension's supported.
 */
static int
generic_nop(void)
{
   _mesa_warning(NULL, "User called no-op dispatch function (an unsupported extension function?)");
   return 0;
}


/**
 * Allocate and initialize a new dispatch table.
 */
static struct _glapi_table *
alloc_dispatch_table(void)
{
   /* Find the larger of Mesa's dispatch table and libGL's dispatch table.
    * In practice, this'll be the same for stand-alone Mesa.  But for DRI
    * Mesa we do this to accomodate different versions of libGL and various
    * DRI drivers.
    */
   GLint numEntries = MAX2(_glapi_get_dispatch_table_size(),
                           sizeof(struct _glapi_table) / sizeof(_glapi_proc));
   struct _glapi_table *table =
      (struct _glapi_table *) _mesa_malloc(numEntries * sizeof(_glapi_proc));
   if (table) {
      _glapi_proc *entry = (_glapi_proc *) table;
      GLint i;
      for (i = 0; i < numEntries; i++) {
         entry[i] = (_glapi_proc) generic_nop;
      }
   }
   return table;
}


/**
 * Initialize a GLcontext struct (rendering context).
 *
 * This includes allocating all the other structs and arrays which hang off of
 * the context by pointers.
 * Note that the driver needs to pass in its dd_function_table here since
 * we need to at least call driverFunctions->NewTextureObject to create the
 * default texture objects.
 * 
 * Called by _mesa_create_context().
 *
 * Performs the imports and exports callback tables initialization, and
 * miscellaneous one-time initializations. If no shared context is supplied one
 * is allocated, and increase its reference count.  Setups the GL API dispatch
 * tables.  Initialize the TNL module. Sets the maximum Z buffer depth.
 * Finally queries the \c MESA_DEBUG and \c MESA_VERBOSE environment variables
 * for debug flags.
 *
 * \param ctx the context to initialize
 * \param visual describes the visual attributes for this context
 * \param share_list points to context to share textures, display lists,
 *        etc with, or NULL
 * \param driverFunctions table of device driver functions for this context
 *        to use
 * \param driverContext pointer to driver-specific context data
 */
GLboolean
_mesa_initialize_context(GLcontext *ctx,
                         const GLvisual *visual,
                         GLcontext *share_list,
                         const struct dd_function_table *driverFunctions,
                         void *driverContext)
{
   ASSERT(driverContext);
   assert(driverFunctions->NewTextureObject);
   assert(driverFunctions->FreeTexImageData);

   /* misc one-time initializations */
   one_time_init(ctx);

   ctx->Visual = *visual;
   ctx->DrawBuffer = NULL;
   ctx->ReadBuffer = NULL;
   ctx->WinSysDrawBuffer = NULL;
   ctx->WinSysReadBuffer = NULL;

   /* Plug in driver functions and context pointer here.
    * This is important because when we call alloc_shared_state() below
    * we'll call ctx->Driver.NewTextureObject() to create the default
    * textures.
    */
   ctx->Driver = *driverFunctions;
   ctx->DriverCtx = driverContext;

   if (share_list) {
      /* share state with another context */
      ctx->Shared = share_list->Shared;
   }
   else {
      /* allocate new, unshared state */
      if (!alloc_shared_state( ctx )) {
         return GL_FALSE;
      }
   }
   _glthread_LOCK_MUTEX(ctx->Shared->Mutex);
   ctx->Shared->RefCount++;
   _glthread_UNLOCK_MUTEX(ctx->Shared->Mutex);

   if (!init_attrib_groups( ctx )) {
      free_shared_state(ctx, ctx->Shared);
      return GL_FALSE;
   }

   /* setup the API dispatch tables */
   ctx->Exec = alloc_dispatch_table();
   ctx->Save = alloc_dispatch_table();
   if (!ctx->Exec || !ctx->Save) {
      free_shared_state(ctx, ctx->Shared);
      if (ctx->Exec)
         _mesa_free(ctx->Exec);
   }
   _mesa_init_exec_table(ctx->Exec);
   ctx->CurrentDispatch = ctx->Exec;
#if _HAVE_FULL_GL
   _mesa_init_dlist_table(ctx->Save);
   _mesa_install_save_vtxfmt( ctx, &ctx->ListState.ListVtxfmt );
   /* Neutral tnl module stuff */
   _mesa_init_exec_vtxfmt( ctx ); 
   ctx->TnlModule.Current = NULL;
   ctx->TnlModule.SwapCount = 0;
#endif

   ctx->FragmentProgram._MaintainTexEnvProgram
      = (_mesa_getenv("MESA_TEX_PROG") != NULL);
   ctx->FragmentProgram._UseTexEnvProgram = ctx->FragmentProgram._MaintainTexEnvProgram;

   ctx->VertexProgram._MaintainTnlProgram
      = (_mesa_getenv("MESA_TNL_PROG") != NULL);
   if (ctx->VertexProgram._MaintainTnlProgram) {
      /* this is required... */
      ctx->FragmentProgram._MaintainTexEnvProgram = GL_TRUE;
   }

   ctx->FirstTimeCurrent = GL_TRUE;

   return GL_TRUE;
}


/**
 * Allocate and initialize a GLcontext structure.
 * Note that the driver needs to pass in its dd_function_table here since
 * we need to at least call driverFunctions->NewTextureObject to initialize
 * the rendering context.
 *
 * \param visual a GLvisual pointer (we copy the struct contents)
 * \param share_list another context to share display lists with or NULL
 * \param driverFunctions points to the dd_function_table into which the
 *        driver has plugged in all its special functions.
 * \param driverCtx points to the device driver's private context state
 * 
 * \return pointer to a new __GLcontextRec or NULL if error.
 */
GLcontext *
_mesa_create_context(const GLvisual *visual,
                     GLcontext *share_list,
                     const struct dd_function_table *driverFunctions,
                     void *driverContext)
{
   GLcontext *ctx;

   ASSERT(visual);
   ASSERT(driverContext);

   ctx = (GLcontext *) _mesa_calloc(sizeof(GLcontext));
   if (!ctx)
      return NULL;

   if (_mesa_initialize_context(ctx, visual, share_list,
                                driverFunctions, driverContext)) {
      return ctx;
   }
   else {
      _mesa_free(ctx);
      return NULL;
   }
}


/**
 * Free the data associated with the given context.
 * 
 * But doesn't free the GLcontext struct itself.
 *
 * \sa _mesa_initialize_context() and init_attrib_groups().
 */
void
_mesa_free_context_data( GLcontext *ctx )
{
   if (!_mesa_get_current_context()){
      /* No current context, but we may need one in order to delete
       * texture objs, etc.  So temporarily bind the context now.
       */
      _mesa_make_current(ctx, NULL, NULL);
   }

   /* unreference WinSysDraw/Read buffers */
   _mesa_unreference_framebuffer(&ctx->WinSysDrawBuffer);
   _mesa_unreference_framebuffer(&ctx->WinSysReadBuffer);
   _mesa_unreference_framebuffer(&ctx->DrawBuffer);
   _mesa_unreference_framebuffer(&ctx->ReadBuffer);

   _mesa_reference_vertprog(ctx, &ctx->VertexProgram.Current, NULL);
   _mesa_reference_vertprog(ctx, &ctx->VertexProgram._Current, NULL);
   _mesa_reference_vertprog(ctx, &ctx->VertexProgram._TnlProgram, NULL);

   _mesa_reference_fragprog(ctx, &ctx->FragmentProgram.Current, NULL);
   _mesa_reference_fragprog(ctx, &ctx->FragmentProgram._Current, NULL);
   _mesa_reference_fragprog(ctx, &ctx->FragmentProgram._TexEnvProgram, NULL);

   _mesa_free_attrib_data(ctx);
   _mesa_free_lighting_data( ctx );
   _mesa_free_eval_data( ctx );
   _mesa_free_texture_data( ctx );
   _mesa_free_matrix_data( ctx );
   _mesa_free_viewport_data( ctx );
   _mesa_free_colortables_data( ctx );
   _mesa_free_program_data(ctx);
   _mesa_free_shader_state(ctx);
   _mesa_free_query_data(ctx);

#if FEATURE_ARB_vertex_buffer_object
   _mesa_delete_buffer_object(ctx, ctx->Array.NullBufferObj);
#endif
   _mesa_delete_array_object(ctx, ctx->Array.DefaultArrayObj);

   /* free dispatch tables */
   _mesa_free(ctx->Exec);
   _mesa_free(ctx->Save);

   /* Shared context state (display lists, textures, etc) */
   _glthread_LOCK_MUTEX(ctx->Shared->Mutex);
   ctx->Shared->RefCount--;
   assert(ctx->Shared->RefCount >= 0);
   _glthread_UNLOCK_MUTEX(ctx->Shared->Mutex);
   if (ctx->Shared->RefCount == 0) {
      /* free shared state */
      free_shared_state( ctx, ctx->Shared );
   }

   if (ctx->Extensions.String)
      _mesa_free((void *) ctx->Extensions.String);

   /* unbind the context if it's currently bound */
   if (ctx == _mesa_get_current_context()) {
      _mesa_make_current(NULL, NULL, NULL);
   }
}


/**
 * Destroy a GLcontext structure.
 *
 * \param ctx GL context.
 * 
 * Calls _mesa_free_context_data() and frees the GLcontext structure itself.
 */
void
_mesa_destroy_context( GLcontext *ctx )
{
   if (ctx) {
      _mesa_free_context_data(ctx);
      _mesa_free( (void *) ctx );
   }
}


#if _HAVE_FULL_GL
/**
 * Copy attribute groups from one context to another.
 * 
 * \param src source context
 * \param dst destination context
 * \param mask bitwise OR of GL_*_BIT flags
 *
 * According to the bits specified in \p mask, copies the corresponding
 * attributes from \p src into \p dst.  For many of the attributes a simple \c
 * memcpy is not enough due to the existence of internal pointers in their data
 * structures.