framebuffer.c

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

   _mesa_bzero(&fb->Visual, sizeof(fb->Visual));
   fb->Visual.rgbMode = GL_TRUE; /* assume this */

#if 0 /* this _might_ be needed */
   if (fb->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
      /* leave visual fields zero'd */
      return;
   }
#endif

   /* find first RGB or CI renderbuffer */
   for (i = 0; i < BUFFER_COUNT; i++) {
      if (fb->Attachment[i].Renderbuffer) {
         const struct gl_renderbuffer *rb = fb->Attachment[i].Renderbuffer;
         if (rb->_BaseFormat == GL_RGBA || rb->_BaseFormat == GL_RGB) {
            fb->Visual.redBits = rb->RedBits;
            fb->Visual.greenBits = rb->GreenBits;
            fb->Visual.blueBits = rb->BlueBits;
            fb->Visual.alphaBits = rb->AlphaBits;
            fb->Visual.rgbBits = fb->Visual.redBits
               + fb->Visual.greenBits + fb->Visual.blueBits;
            fb->Visual.floatMode = GL_FALSE;
            break;
         }
         else if (rb->_BaseFormat == GL_COLOR_INDEX) {
            fb->Visual.indexBits = rb->IndexBits;
            fb->Visual.rgbMode = GL_FALSE;
            break;
         }
      }
   }

   if (fb->Attachment[BUFFER_DEPTH].Renderbuffer) {
      fb->Visual.haveDepthBuffer = GL_TRUE;
      fb->Visual.depthBits
         = fb->Attachment[BUFFER_DEPTH].Renderbuffer->DepthBits;
   }

   if (fb->Attachment[BUFFER_STENCIL].Renderbuffer) {
      fb->Visual.haveStencilBuffer = GL_TRUE;
      fb->Visual.stencilBits
         = fb->Attachment[BUFFER_STENCIL].Renderbuffer->StencilBits;
   }

   if (fb->Attachment[BUFFER_ACCUM].Renderbuffer) {
      fb->Visual.haveAccumBuffer = GL_TRUE;
      fb->Visual.accumRedBits
         = fb->Attachment[BUFFER_ACCUM].Renderbuffer->RedBits;
      fb->Visual.accumGreenBits
         = fb->Attachment[BUFFER_ACCUM].Renderbuffer->GreenBits;
      fb->Visual.accumBlueBits
         = fb->Attachment[BUFFER_ACCUM].Renderbuffer->BlueBits;
      fb->Visual.accumAlphaBits
         = fb->Attachment[BUFFER_ACCUM].Renderbuffer->AlphaBits;
   }

   compute_depth_max(fb);
}


/**
 * Update the framebuffer's _DepthBuffer field using the renderbuffer
 * found at the given attachment index.
 *
 * If that attachment points to a combined GL_DEPTH_STENCIL renderbuffer,
 * create and install a depth wrapper/adaptor.
 *
 * \param fb  the framebuffer whose _DepthBuffer field to update
 * \param attIndex  indicates the renderbuffer to possibly wrap
 */
void
_mesa_update_depth_buffer(GLcontext *ctx,
                          struct gl_framebuffer *fb,
                          GLuint attIndex)
{
   struct gl_renderbuffer *depthRb;

   /* only one possiblity for now */
   ASSERT(attIndex == BUFFER_DEPTH);

   depthRb = fb->Attachment[attIndex].Renderbuffer;

   if (depthRb && depthRb->_ActualFormat == GL_DEPTH24_STENCIL8_EXT) {
      /* The attached depth buffer is a GL_DEPTH_STENCIL renderbuffer */
      if (!fb->_DepthBuffer
          || fb->_DepthBuffer->Wrapped != depthRb
          || fb->_DepthBuffer->_BaseFormat != GL_DEPTH_COMPONENT) {
         /* need to update wrapper */
         struct gl_renderbuffer *wrapper
            = _mesa_new_z24_renderbuffer_wrapper(ctx, depthRb);
         _mesa_reference_renderbuffer(&fb->_DepthBuffer, wrapper);
         ASSERT(fb->_DepthBuffer->Wrapped == depthRb);
      }
   }
   else {
      /* depthRb may be null */
      _mesa_reference_renderbuffer(&fb->_DepthBuffer, depthRb);
   }
}


/**
 * Update the framebuffer's _StencilBuffer field using the renderbuffer
 * found at the given attachment index.
 *
 * If that attachment points to a combined GL_DEPTH_STENCIL renderbuffer,
 * create and install a stencil wrapper/adaptor.
 *
 * \param fb  the framebuffer whose _StencilBuffer field to update
 * \param attIndex  indicates the renderbuffer to possibly wrap
 */
void
_mesa_update_stencil_buffer(GLcontext *ctx,
                            struct gl_framebuffer *fb,
                            GLuint attIndex)
{
   struct gl_renderbuffer *stencilRb;

   ASSERT(attIndex == BUFFER_DEPTH ||
          attIndex == BUFFER_STENCIL);

   stencilRb = fb->Attachment[attIndex].Renderbuffer;

   if (stencilRb && stencilRb->_ActualFormat == GL_DEPTH24_STENCIL8_EXT) {
      /* The attached stencil buffer is a GL_DEPTH_STENCIL renderbuffer */
      if (!fb->_StencilBuffer
          || fb->_StencilBuffer->Wrapped != stencilRb
          || fb->_StencilBuffer->_BaseFormat != GL_STENCIL_INDEX) {
         /* need to update wrapper */
         struct gl_renderbuffer *wrapper
            = _mesa_new_s8_renderbuffer_wrapper(ctx, stencilRb);
         _mesa_reference_renderbuffer(&fb->_StencilBuffer, wrapper);
         ASSERT(fb->_StencilBuffer->Wrapped == stencilRb);
      }
   }
   else {
      /* stencilRb may be null */
      _mesa_reference_renderbuffer(&fb->_StencilBuffer, stencilRb);
   }
}


/*
 * Example DrawBuffers scenarios:
 *
 * 1. glDrawBuffer(GL_FRONT_AND_BACK), fixed-func or shader writes to
 * "gl_FragColor" or program writes to the "result.color" register:
 *
 *   fragment color output   renderbuffer
 *   ---------------------   ---------------
 *   color[0]                Front, Back
 *
 *
 * 2. glDrawBuffers(3, [GL_FRONT, GL_AUX0, GL_AUX1]), shader writes to
 * gl_FragData[i] or program writes to result.color[i] registers:
 *
 *   fragment color output   renderbuffer
 *   ---------------------   ---------------
 *   color[0]                Front
 *   color[1]                Aux0
 *   color[3]                Aux1
 *
 *
 * 3. glDrawBuffers(3, [GL_FRONT, GL_AUX0, GL_AUX1]) and shader writes to
 * gl_FragColor, or fixed function:
 *
 *   fragment color output   renderbuffer
 *   ---------------------   ---------------
 *   color[0]                Front, Aux0, Aux1
 *
 *
 * In either case, the list of renderbuffers is stored in the
 * framebuffer->_ColorDrawBuffers[] array and
 * framebuffer->_NumColorDrawBuffers indicates the number of buffers.
 * The renderer (like swrast) has to look at the current fragment shader
 * to see if it writes to gl_FragColor vs. gl_FragData[i] to determine
 * how to map color outputs to renderbuffers.
 *
 * Note that these two calls are equivalent (for fixed function fragment
 * shading anyway):
 *   a)  glDrawBuffer(GL_FRONT_AND_BACK);  (assuming non-stereo framebuffer)
 *   b)  glDrawBuffers(2, [GL_FRONT_LEFT, GL_BACK_LEFT]);
 */




/**
 * Update the (derived) list of color drawing renderbuffer pointers.
 * Later, when we're rendering we'll loop from 0 to _NumColorDrawBuffers
 * writing colors.
 */
static void
update_color_draw_buffers(GLcontext *ctx, struct gl_framebuffer *fb)
{
   GLuint output;

   /* set 0th buffer to NULL now in case _NumColorDrawBuffers is zero */
   fb->_ColorDrawBuffers[0] = NULL;

   for (output = 0; output < fb->_NumColorDrawBuffers; output++) {
      GLint buf = fb->_ColorDrawBufferIndexes[output];
      if (buf >= 0) {
         fb->_ColorDrawBuffers[output] = fb->Attachment[buf].Renderbuffer;
      }
      else {
         fb->_ColorDrawBuffers[output] = NULL;
      }
   }
}


/**
 * Update the (derived) color read renderbuffer pointer.
 * Unlike the DrawBuffer, we can only read from one (or zero) color buffers.
 */
static void
update_color_read_buffer(GLcontext *ctx, struct gl_framebuffer *fb)
{
   (void) ctx;
   if (fb->_ColorReadBufferIndex == -1 ||
       fb->DeletePending ||
       fb->Width == 0 ||
       fb->Height == 0) {
      fb->_ColorReadBuffer = NULL; /* legal! */
   }
   else {
      ASSERT(fb->_ColorReadBufferIndex >= 0);
      ASSERT(fb->_ColorReadBufferIndex < BUFFER_COUNT);
      fb->_ColorReadBuffer
         = fb->Attachment[fb->_ColorReadBufferIndex].Renderbuffer;
   }
}


/**
 * Update a gl_framebuffer's derived state.
 *
 * Specifically, update these framebuffer fields:
 *    _ColorDrawBuffers
 *    _NumColorDrawBuffers
 *    _ColorReadBuffer
 *    _DepthBuffer
 *    _StencilBuffer
 *
 * If the framebuffer is user-created, make sure it's complete.
 *
 * The following functions (at least) can effect framebuffer state:
 * glReadBuffer, glDrawBuffer, glDrawBuffersARB, glFramebufferRenderbufferEXT,
 * glRenderbufferStorageEXT.
 */
static void
update_framebuffer(GLcontext *ctx, struct gl_framebuffer *fb)
{
   if (fb->Name == 0) {
      /* This is a window-system framebuffer */
      /* Need to update the FB's GL_DRAW_BUFFER state to match the
       * context state (GL_READ_BUFFER too).
       */
      if (fb->ColorDrawBuffer[0] != ctx->Color.DrawBuffer[0]) {
         _mesa_drawbuffers(ctx, ctx->Const.MaxDrawBuffers,
                           ctx->Color.DrawBuffer, NULL);
      }
      if (fb->ColorReadBuffer != ctx->Pixel.ReadBuffer) {
         
      }
   }
   else {
      /* This is a user-created framebuffer.
       * Completeness only matters for user-created framebuffers.
       */
      _mesa_test_framebuffer_completeness(ctx, fb);
      _mesa_update_framebuffer_visual(fb);
   }

   /* Strictly speaking, we don't need to update the draw-state
    * if this FB is bound as ctx->ReadBuffer (and conversely, the
    * read-state if this FB is bound as ctx->DrawBuffer), but no
    * harm.
    */
   update_color_draw_buffers(ctx, fb);
   update_color_read_buffer(ctx, fb);
   _mesa_update_depth_buffer(ctx, fb, BUFFER_DEPTH);
   _mesa_update_stencil_buffer(ctx, fb, BUFFER_STENCIL);

   compute_depth_max(fb);
}


/**
 * Update state related to the current draw/read framebuffers.
 */
void
_mesa_update_framebuffer(GLcontext *ctx)
{
   struct gl_framebuffer *drawFb = ctx->DrawBuffer;
   struct gl_framebuffer *readFb = ctx->ReadBuffer;

   update_framebuffer(ctx, drawFb);
   if (readFb != drawFb)
      update_framebuffer(ctx, readFb);
}


/**
 * Check if the renderbuffer for a read operation (glReadPixels, glCopyPixels,
 * glCopyTex[Sub]Image, etc. exists.
 * \param format  a basic image format such as GL_RGB, GL_RGBA, GL_ALPHA,
 *                GL_DEPTH_COMPONENT, etc. or GL_COLOR, GL_DEPTH, GL_STENCIL.
 * \return GL_TRUE if buffer exists, GL_FALSE otherwise
 */
GLboolean
_mesa_source_buffer_exists(GLcontext *ctx, GLenum format)
{
   const struct gl_renderbuffer_attachment *att
      = ctx->ReadBuffer->Attachment;

   if (ctx->ReadBuffer->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
      return GL_FALSE;
   }

   switch (format) {
   case GL_COLOR:
   case GL_RED:
   case GL_GREEN:
   case GL_BLUE:
   case GL_ALPHA:
   case GL_LUMINANCE:
   case GL_LUMINANCE_ALPHA:
   case GL_INTENSITY:
   case GL_RGB:
   case GL_BGR:
   case GL_RGBA:
   case GL_BGRA:
   case GL_ABGR_EXT:
   case GL_COLOR_INDEX:
      if (ctx->ReadBuffer->_ColorReadBuffer == NULL) {
         return GL_FALSE;
      }
      /* XXX enable this post 6.5 release:
      ASSERT(ctx->ReadBuffer->_ColorReadBuffer->RedBits > 0 ||
             ctx->ReadBuffer->_ColorReadBuffer->IndexBits > 0);
      */
      break;
   case GL_DEPTH:
   case GL_DEPTH_COMPONENT:
      if (!att[BUFFER_DEPTH].Renderbuffer) {
         return GL_FALSE;
      }
      ASSERT(att[BUFFER_DEPTH].Renderbuffer->DepthBits > 0);
      break;
   case GL_STENCIL:
   case GL_STENCIL_INDEX:
      if (!att[BUFFER_STENCIL].Renderbuffer) {
         return GL_FALSE;
      }
      ASSERT(att[BUFFER_STENCIL].Renderbuffer->StencilBits > 0);
      break;
   case GL_DEPTH_STENCIL_EXT:
      if (!att[BUFFER_DEPTH].Renderbuffer ||
          !att[BUFFER_STENCIL].Renderbuffer) {
         return GL_FALSE;
      }
      ASSERT(att[BUFFER_DEPTH].Renderbuffer->DepthBits > 0);
      ASSERT(att[BUFFER_STENCIL].Renderbuffer->StencilBits > 0);
      break;
   default:
      _mesa_problem(ctx,
                    "Unexpected format 0x%x in _mesa_source_buffer_exists",
                    format);
      return GL_FALSE;
   }

   /* OK */
   return GL_TRUE;
}


/**
 * As above, but for drawing operations.
 * XXX code do some code merging w/ above function.
 */
GLboolean
_mesa_dest_buffer_exists(GLcontext *ctx, GLenum format)
{
   const struct gl_renderbuffer_attachment *att
      = ctx->ReadBuffer->Attachment;

   if (ctx->DrawBuffer->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
      return GL_FALSE;
   }

   switch (format) {
   case GL_COLOR:
   case GL_RED:
   case GL_GREEN:
   case GL_BLUE:
   case GL_ALPHA:
   case GL_LUMINANCE:
   case GL_LUMINANCE_ALPHA:
   case GL_INTENSITY:
   case GL_RGB:
   case GL_BGR:
   case GL_RGBA:
   case GL_BGRA:
   case GL_ABGR_EXT:
   case GL_COLOR_INDEX:
      /* nothing special */
      /* Could assert that colorbuffer has RedBits > 0 */
      break;
   case GL_DEPTH:
   case GL_DEPTH_COMPONENT:
      if (!att[BUFFER_DEPTH].Renderbuffer) {
         return GL_FALSE;
      }
      ASSERT(att[BUFFER_DEPTH].Renderbuffer->DepthBits > 0);
      break;
   case GL_STENCIL:
   case GL_STENCIL_INDEX:
      if (!att[BUFFER_STENCIL].Renderbuffer) {
         return GL_FALSE;
      }
      ASSERT(att[BUFFER_STENCIL].Renderbuffer->StencilBits > 0);
      break;
   case GL_DEPTH_STENCIL_EXT:
      if (!att[BUFFER_DEPTH].Renderbuffer ||
          !att[BUFFER_STENCIL].Renderbuffer) {
         return GL_FALSE;
      }
      ASSERT(att[BUFFER_DEPTH].Renderbuffer->DepthBits > 0);
      ASSERT(att[BUFFER_STENCIL].Renderbuffer->StencilBits > 0);
      break;
   default:
      _mesa_problem(ctx,
                    "Unexpected format 0x%x in _mesa_source_buffer_exists",
                    format);
      return GL_FALSE;
   }

   /* OK */
   return GL_TRUE;
}