svn merge ^/branches/released . --username marha

1 files changed, 961 insertions, 0 deletions

diff --git a/mesalib/src/mesa/main/framebuffer.c b/mesalib/src/mesa/main/framebuffer.c
new file mode 100644
index 000000000..dc79b8ca6
--- /dev/null
+++ b/mesalib/src/mesa/main/framebuffer.c
@@ -0,0 +1,961 @@
+/*
+ * Mesa 3-D graphics library
+ * Version:  7.2
+ *
+ * Copyright (C) 1999-2008  Brian Paul   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 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.
+ */
+
+
+/**
+ * Functions for allocating/managing framebuffers and renderbuffers.
+ * Also, routines for reading/writing renderbuffer data as ubytes,
+ * ushorts, uints, etc.
+ */
+
+
+#include "glheader.h"
+#include "imports.h"
+#include "buffers.h"
+#include "context.h"
+#include "depthstencil.h"
+#include "macros.h"
+#include "mtypes.h"
+#include "fbobject.h"
+#include "framebuffer.h"
+#include "renderbuffer.h"
+#include "texobj.h"
+
+
+
+/**
+ * Compute/set the _DepthMax field for the given framebuffer.
+ * This value depends on the Z buffer resolution.
+ */
+static void
+compute_depth_max(struct gl_framebuffer *fb)
+{
+   if (fb->Visual.depthBits == 0) {
+      /* Special case.  Even if we don't have a depth buffer we need
+       * good values for DepthMax for Z vertex transformation purposes
+       * and for per-fragment fog computation.
+       */
+      fb->_DepthMax = (1 << 16) - 1;
+   }
+   else if (fb->Visual.depthBits < 32) {
+      fb->_DepthMax = (1 << fb->Visual.depthBits) - 1;
+   }
+   else {
+      /* Special case since shift values greater than or equal to the
+       * number of bits in the left hand expression's type are undefined.
+       */
+      fb->_DepthMax = 0xffffffff;
+   }
+   fb->_DepthMaxF = (GLfloat) fb->_DepthMax;
+
+   /* Minimum resolvable depth value, for polygon offset */
+   fb->_MRD = (GLfloat)1.0 / fb->_DepthMaxF;
+}
+
+
+/**
+ * Create and initialize a gl_framebuffer object.
+ * This is intended for creating _window_system_ framebuffers, not generic
+ * framebuffer objects ala GL_EXT_framebuffer_object.
+ *
+ * \sa _mesa_new_framebuffer
+ */
+struct gl_framebuffer *
+_mesa_create_framebuffer(const GLvisual *visual)
+{
+   struct gl_framebuffer *fb = CALLOC_STRUCT(gl_framebuffer);
+   assert(visual);
+   if (fb) {
+      _mesa_initialize_framebuffer(fb, visual);
+   }
+   return fb;
+}
+
+
+/**
+ * Allocate a new gl_framebuffer object.
+ * This is the default function for ctx->Driver.NewFramebuffer().
+ * This is for allocating user-created framebuffers, not window-system
+ * framebuffers!
+ * \sa _mesa_create_framebuffer
+ */
+struct gl_framebuffer *
+_mesa_new_framebuffer(GLcontext *ctx, GLuint name)
+{
+   struct gl_framebuffer *fb;
+   (void) ctx;
+   assert(name != 0);
+   fb = CALLOC_STRUCT(gl_framebuffer);
+   if (fb) {
+      fb->Name = name;
+      fb->RefCount = 1;
+      fb->_NumColorDrawBuffers = 1;
+      fb->ColorDrawBuffer[0] = GL_COLOR_ATTACHMENT0_EXT;
+      fb->_ColorDrawBufferIndexes[0] = BUFFER_COLOR0;
+      fb->ColorReadBuffer = GL_COLOR_ATTACHMENT0_EXT;
+      fb->_ColorReadBufferIndex = BUFFER_COLOR0;
+      fb->Delete = _mesa_destroy_framebuffer;
+      _glthread_INIT_MUTEX(fb->Mutex);
+   }
+   return fb;
+}
+
+
+/**
+ * Initialize a gl_framebuffer object.  Typically used to initialize
+ * window system-created framebuffers, not user-created framebuffers.
+ * \sa _mesa_create_framebuffer
+ */
+void
+_mesa_initialize_framebuffer(struct gl_framebuffer *fb, const GLvisual *visual)
+{
+   assert(fb);
+   assert(visual);
+
+   _mesa_bzero(fb, sizeof(struct gl_framebuffer));
+
+   _glthread_INIT_MUTEX(fb->Mutex);
+
+   fb->RefCount = 1;
+
+   /* save the visual */
+   fb->Visual = *visual;
+
+   /* Init read/draw renderbuffer state */
+   if (visual->doubleBufferMode) {
+      fb->_NumColorDrawBuffers = 1;
+      fb->ColorDrawBuffer[0] = GL_BACK;
+      fb->_ColorDrawBufferIndexes[0] = BUFFER_BACK_LEFT;
+      fb->ColorReadBuffer = GL_BACK;
+      fb->_ColorReadBufferIndex = BUFFER_BACK_LEFT;
+   }
+   else {
+      fb->_NumColorDrawBuffers = 1;
+      fb->ColorDrawBuffer[0] = GL_FRONT;
+      fb->_ColorDrawBufferIndexes[0] = BUFFER_FRONT_LEFT;
+      fb->ColorReadBuffer = GL_FRONT;
+      fb->_ColorReadBufferIndex = BUFFER_FRONT_LEFT;
+   }
+
+   fb->Delete = _mesa_destroy_framebuffer;
+   fb->_Status = GL_FRAMEBUFFER_COMPLETE_EXT;
+
+   compute_depth_max(fb);
+}
+
+
+/**
+ * Deallocate buffer and everything attached to it.
+ * Typically called via the gl_framebuffer->Delete() method.
+ */
+void
+_mesa_destroy_framebuffer(struct gl_framebuffer *fb)
+{
+   if (fb) {
+      _mesa_free_framebuffer_data(fb);
+      _mesa_free(fb);
+   }
+}
+
+
+/**
+ * Free all the data hanging off the given gl_framebuffer, but don't free
+ * the gl_framebuffer object itself.
+ */
+void
+_mesa_free_framebuffer_data(struct gl_framebuffer *fb)
+{
+   GLuint i;
+
+   assert(fb);
+   assert(fb->RefCount == 0);
+
+   _glthread_DESTROY_MUTEX(fb->Mutex);
+
+   for (i = 0; i < BUFFER_COUNT; i++) {
+      struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
+      if (att->Renderbuffer) {
+         _mesa_reference_renderbuffer(&att->Renderbuffer, NULL);
+      }
+      if (att->Texture) {
+         _mesa_reference_texobj(&att->Texture, NULL);
+      }
+      ASSERT(!att->Renderbuffer);
+      ASSERT(!att->Texture);
+      att->Type = GL_NONE;
+   }
+
+   /* unbind _Depth/_StencilBuffer to decr ref counts */
+   _mesa_reference_renderbuffer(&fb->_DepthBuffer, NULL);
+   _mesa_reference_renderbuffer(&fb->_StencilBuffer, NULL);
+}
+
+
+/**
+ * Set *ptr to point to fb, with refcounting and locking.
+ */
+void
+_mesa_reference_framebuffer(struct gl_framebuffer **ptr,
+                            struct gl_framebuffer *fb)
+{
+   assert(ptr);
+   if (*ptr == fb) {
+      /* no change */
+      return;
+   }
+
+   if (*ptr) {
+      /* unreference old renderbuffer */
+      GLboolean deleteFlag = GL_FALSE;
+      struct gl_framebuffer *oldFb = *ptr;
+
+      _glthread_LOCK_MUTEX(oldFb->Mutex);
+      ASSERT(oldFb->RefCount > 0);
+      oldFb->RefCount--;
+      deleteFlag = (oldFb->RefCount == 0);
+      _glthread_UNLOCK_MUTEX(oldFb->Mutex);
+      
+      if (deleteFlag)
+         oldFb->Delete(oldFb);
+
+      *ptr = NULL;
+   }
+   assert(!*ptr);
+
+   if (fb) {
+      _glthread_LOCK_MUTEX(fb->Mutex);
+      fb->RefCount++;
+      _glthread_UNLOCK_MUTEX(fb->Mutex);
+      *ptr = fb;
+   }
+}
+
+
+/**
+ * Resize the given framebuffer's renderbuffers to the new width and height.
+ * This should only be used for window-system framebuffers, not
+ * user-created renderbuffers (i.e. made with GL_EXT_framebuffer_object).
+ * This will typically be called via ctx->Driver.ResizeBuffers() or directly
+ * from a device driver.
+ *
+ * \note it's possible for ctx to be null since a window can be resized
+ * without a currently bound rendering context.
+ */
+void
+_mesa_resize_framebuffer(GLcontext *ctx, struct gl_framebuffer *fb,
+                         GLuint width, GLuint height)
+{
+   GLuint i;
+
+   /* XXX I think we could check if the size is not changing
+    * and return early.
+    */
+
+   /* For window system framebuffers, Name is zero */
+   assert(fb->Name == 0);
+
+   for (i = 0; i < BUFFER_COUNT; i++) {
+      struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
+      if (att->Type == GL_RENDERBUFFER_EXT && att->Renderbuffer) {
+         struct gl_renderbuffer *rb = att->Renderbuffer;
+         /* only resize if size is changing */
+         if (rb->Width != width || rb->Height != height) {
+            /* could just as well pass rb->_ActualFormat here */
+            if (rb->AllocStorage(ctx, rb, rb->InternalFormat, width, height)) {
+               ASSERT(rb->Width == width);
+               ASSERT(rb->Height == height);
+            }
+            else {
+               _mesa_error(ctx, GL_OUT_OF_MEMORY, "Resizing framebuffer");
+               /* no return */
+            }
+         }
+      }
+   }
+
+   if (fb->_DepthBuffer) {
+      struct gl_renderbuffer *rb = fb->_DepthBuffer;
+      if (rb->Width != width || rb->Height != height) {
+         if (!rb->AllocStorage(ctx, rb, rb->InternalFormat, width, height)) {
+            _mesa_error(ctx, GL_OUT_OF_MEMORY, "Resizing framebuffer");
+         }
+      }
+   }
+
+   if (fb->_StencilBuffer) {
+      struct gl_renderbuffer *rb = fb->_StencilBuffer;
+      if (rb->Width != width || rb->Height != height) {
+         if (!rb->AllocStorage(ctx, rb, rb->InternalFormat, width, height)) {
+            _mesa_error(ctx, GL_OUT_OF_MEMORY, "Resizing framebuffer");
+         }
+      }
+   }
+
+   fb->Width = width;
+   fb->Height = height;
+
+   if (ctx) {
+      /* update scissor / window bounds */
+      _mesa_update_draw_buffer_bounds(ctx);
+      /* Signal new buffer state so that swrast will update its clipping
+       * info (the CLIP_BIT flag).
+       */
+      ctx->NewState |= _NEW_BUFFERS;
+   }
+}
+
+
+
+/**
+ * XXX THIS IS OBSOLETE - drivers should take care of detecting window
+ * size changes and act accordingly, likely calling _mesa_resize_framebuffer().
+ *
+ * GL_MESA_resize_buffers extension.
+ *
+ * When this function is called, we'll ask the window system how large
+ * the current window is.  If it's a new size, we'll call the driver's
+ * ResizeBuffers function.  The driver will then resize its color buffers
+ * as needed, and maybe call the swrast's routine for reallocating
+ * swrast-managed depth/stencil/accum/etc buffers.
+ * \note This function should only be called through the GL API, not
+ * from device drivers (as was done in the past).
+ */
+void
+_mesa_resizebuffers( GLcontext *ctx )
+{
+   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH( ctx );
+
+   if (MESA_VERBOSE & VERBOSE_API)
+      _mesa_debug(ctx, "glResizeBuffersMESA\n");
+
+   if (!ctx->Driver.GetBufferSize) {
+      return;
+   }
+
+   if (ctx->WinSysDrawBuffer) {
+      GLuint newWidth, newHeight;
+      GLframebuffer *buffer = ctx->WinSysDrawBuffer;
+
+      assert(buffer->Name == 0);
+
+      /* ask device driver for size of output buffer */
+      ctx->Driver.GetBufferSize( buffer, &newWidth, &newHeight );
+
+      /* see if size of device driver's color buffer (window) has changed */
+      if (buffer->Width != newWidth || buffer->Height != newHeight) {
+         if (ctx->Driver.ResizeBuffers)
+            ctx->Driver.ResizeBuffers(ctx, buffer, newWidth, newHeight );
+      }
+   }
+
+   if (ctx->WinSysReadBuffer
+       && ctx->WinSysReadBuffer != ctx->WinSysDrawBuffer) {
+      GLuint newWidth, newHeight;
+      GLframebuffer *buffer = ctx->WinSysReadBuffer;
+
+      assert(buffer->Name == 0);
+
+      /* ask device driver for size of read buffer */
+      ctx->Driver.GetBufferSize( buffer, &newWidth, &newHeight );
+
+      /* see if size of device driver's color buffer (window) has changed */
+      if (buffer->Width != newWidth || buffer->Height != newHeight) {
+         if (ctx->Driver.ResizeBuffers)
+            ctx->Driver.ResizeBuffers(ctx, buffer, newWidth, newHeight );
+      }
+   }
+
+   ctx->NewState |= _NEW_BUFFERS;  /* to update scissor / window bounds */
+}
+
+
+/*
+ * XXX THIS IS OBSOLETE
+ */
+void GLAPIENTRY
+_mesa_ResizeBuffersMESA( void )
+{
+   GET_CURRENT_CONTEXT(ctx);
+
+   if (ctx->Extensions.MESA_resize_buffers)
+      _mesa_resizebuffers( ctx );
+}
+
+
+
+/**
+ * Examine all the framebuffer's renderbuffers to update the Width/Height
+ * fields of the framebuffer.  If we have renderbuffers with different
+ * sizes, set the framebuffer's width and height to the min size.
+ * Note: this is only intended for user-created framebuffers, not
+ * window-system framebuffes.
+ */
+static void
+update_framebuffer_size(GLcontext *ctx, struct gl_framebuffer *fb)
+{
+   GLuint minWidth = ~0, minHeight = ~0;
+   GLuint i;
+
+   /* user-created framebuffers only */
+   assert(fb->Name);
+
+   for (i = 0; i < BUFFER_COUNT; i++) {
+      struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
+      const struct gl_renderbuffer *rb = att->Renderbuffer;
+      if (rb) {
+         minWidth = MIN2(minWidth, rb->Width);
+         minHeight = MIN2(minHeight, rb->Height);
+      }
+   }
+
+   if (minWidth != ~0) {
+      fb->Width = minWidth;
+      fb->Height = minHeight;
+   }
+   else {
+      fb->Width = 0;
+      fb->Height = 0;
+   }
+}
+
+
+/**
+ * Update the context's current drawing buffer's Xmin, Xmax, Ymin, Ymax fields.
+ * These values are computed from the buffer's width and height and
+ * the scissor box, if it's enabled.
+ * \param ctx  the GL context.
+ */
+void
+_mesa_update_draw_buffer_bounds(GLcontext *ctx)
+{
+   struct gl_framebuffer *buffer = ctx->DrawBuffer;
+
+   if (!buffer)
+      return;
+
+   if (buffer->Name) {
+      /* user-created framebuffer size depends on the renderbuffers */
+      update_framebuffer_size(ctx, buffer);
+   }
+
+   buffer->_Xmin = 0;
+   buffer->_Ymin = 0;
+   buffer->_Xmax = buffer->Width;
+   buffer->_Ymax = buffer->Height;
+
+   if (ctx->Scissor.Enabled) {
+      if (ctx->Scissor.X > buffer->_Xmin) {
+	 buffer->_Xmin = ctx->Scissor.X;
+      }
+      if (ctx->Scissor.Y > buffer->_Ymin) {
+	 buffer->_Ymin = ctx->Scissor.Y;
+      }
+      if (ctx->Scissor.X + ctx->Scissor.Width < buffer->_Xmax) {
+	 buffer->_Xmax = ctx->Scissor.X + ctx->Scissor.Width;
+      }
+      if (ctx->Scissor.Y + ctx->Scissor.Height < buffer->_Ymax) {
+	 buffer->_Ymax = ctx->Scissor.Y + ctx->Scissor.Height;
+      }
+      /* finally, check for empty region */
+      if (buffer->_Xmin > buffer->_Xmax) {
+         buffer->_Xmin = buffer->_Xmax;
+      }
+      if (buffer->_Ymin > buffer->_Ymax) {
+         buffer->_Ymin = buffer->_Ymax;
+      }
+   }
+
+   ASSERT(buffer->_Xmin <= buffer->_Xmax);
+   ASSERT(buffer->_Ymin <= buffer->_Ymax);
+}
+
+
+/**
+ * The glGet queries of the framebuffer red/green/blue size, stencil size,
+ * etc. are satisfied by the fields of ctx->DrawBuffer->Visual.  These can
+ * change depending on the renderbuffer bindings.  This function updates
+ * the given framebuffer's Visual from the current renderbuffer bindings.
+ *
+ * This may apply to user-created framebuffers or window system framebuffers.
+ *
+ * Also note: ctx->DrawBuffer->Visual.depthBits might not equal
+ * ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer.DepthBits.
+ * The former one is used to convert floating point depth values into
+ * integer Z values.
+ */
+void
+_mesa_update_framebuffer_visual(struct gl_framebuffer *fb)
+{
+   GLuint i;
+
+   _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;
+            fb->Visual.samples = rb->NumSamples;
+            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.
+       */
+      if (fb->_Status != GL_FRAMEBUFFER_COMPLETE) {
+         _mesa_test_framebuffer_completeness(ctx, 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 we don't know the framebuffer status, update it now */
+   if (ctx->ReadBuffer->_Status == 0) {
+      _mesa_test_framebuffer_completeness(ctx, ctx->ReadBuffer);
+   }
+
+   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;
+      }
+      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 could do some code merging w/ above function.
+ */
+GLboolean
+_mesa_dest_buffer_exists(GLcontext *ctx, GLenum format)
+{
+   const struct gl_renderbuffer_attachment *att = ctx->DrawBuffer->Attachment;
+
+   /* If we don't know the framebuffer status, update it now */
+   if (ctx->DrawBuffer->_Status == 0) {
+      _mesa_test_framebuffer_completeness(ctx, ctx->DrawBuffer);
+   }
+
+   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 since GL_DRAW_BUFFER could be GL_NONE. */
+      /* 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_dest_buffer_exists",
+                    format);
+      return GL_FALSE;
+   }
+
+   /* OK */
+   return GL_TRUE;
+}