1 files changed, 77 insertions, 20 deletions

diff --git a/src/mesa/main/buffers.c b/src/mesa/main/buffers.c
index c280f89e1d1..d9c18bfaafc 100644
--- a/src/mesa/main/buffers.c
+++ b/src/mesa/main/buffers.c
@@ -140,7 +140,9 @@ _mesa_Clear( GLbitfield mask )
       return;
    }
 
-   if (ctx->DrawBuffer->Width == 0 || ctx->DrawBuffer->Height == 0)
+   if (ctx->DrawBuffer->Width == 0 || ctx->DrawBuffer->Height == 0 ||
+       ctx->DrawBuffer->_Xmin >= ctx->DrawBuffer->_Xmax ||
+       ctx->DrawBuffer->_Ymin >= ctx->DrawBuffer->_Ymax)
       return;
 
    if (ctx->RenderMode == GL_RENDER) {
@@ -336,6 +338,20 @@ read_buffer_enum_to_index(GLenum buffer)
  * \sa _mesa_DrawBuffersARB
  *
  * \param buffer  buffer token such as GL_LEFT or GL_FRONT_AND_BACK, etc.
+ *
+ * Note that the behaviour of this function depends on whether the
+ * current ctx->DrawBuffer is a window-system framebuffer (Name=0) or
+ * a user-created framebuffer object (Name!=0).
+ *   In the former case, we update the per-context ctx->Color.DrawBuffer
+ *   state var _and_ the FB's ColorDrawBuffer state.
+ *   In the later case, we update the FB's ColorDrawBuffer state only.
+ *
+ * Furthermore, upon a MakeCurrent() or BindFramebuffer() call, if the
+ * new FB is a window system FB, we need to re-update the FB's
+ * ColorDrawBuffer state to match the context.  This is handled in
+ * _mesa_update_framebuffer().
+ *
+ * See the GL_EXT_framebuffer_object spec for more info.
  */
 void GLAPIENTRY
 _mesa_DrawBuffer(GLenum buffer)
@@ -370,6 +386,14 @@ _mesa_DrawBuffer(GLenum buffer)
 
    /* if we get here, there's no error so set new state */
    _mesa_drawbuffers(ctx, 1, &buffer, &destMask);
+
+   /*
+    * Call device driver function.
+    */
+   if (ctx->Driver.DrawBuffers)
+      ctx->Driver.DrawBuffers(ctx, 1, &buffer);
+   else if (ctx->Driver.DrawBuffer)
+      ctx->Driver.DrawBuffer(ctx, buffer);
 }
 
 
@@ -435,6 +459,14 @@ _mesa_DrawBuffersARB(GLsizei n, const GLenum *buffers)
 
    /* OK, if we get here, there were no errors so set the new state */
    _mesa_drawbuffers(ctx, n, buffers, destMask);
+
+   /*
+    * Call device driver function.
+    */
+   if (ctx->Driver.DrawBuffers)
+      ctx->Driver.DrawBuffers(ctx, n, buffers);
+   else if (ctx->Driver.DrawBuffer)
+      ctx->Driver.DrawBuffer(ctx, buffers[0]);
 }
 
 
@@ -463,16 +495,22 @@ set_color_output(GLcontext *ctx, GLuint output, GLenum buffer,
    /* not really needed, will be set later */
    fb->_NumColorDrawBuffers[output] = 0;
 
-   /* Set traditional state var */
-   ctx->Color.DrawBuffer[output] = buffer;
+   if (fb->Name == 0) {
+      /* Only set the per-context DrawBuffer state if we're currently
+       * drawing to a window system framebuffer.
+       */
+      ctx->Color.DrawBuffer[output] = buffer;
+   }
 }
 
 
 /**
- * Helper routine used by _mesa_DrawBuffer, _mesa_DrawBuffersARB and
- * _mesa_PopAttrib to set drawbuffer state.
+ * Helper function to set the GL_DRAW_BUFFER state in the context and
+ * current FBO.
+ *
  * All error checking will have been done prior to calling this function
  * so nothing should go wrong at this point.
+ *
  * \param ctx  current context
  * \param n    number of color outputs to set
  * \param buffers  array[n] of colorbuffer names, like GL_LEFT.
@@ -509,14 +547,32 @@ _mesa_drawbuffers(GLcontext *ctx, GLuint n, const GLenum *buffers,
    }
 
    ctx->NewState |= _NEW_COLOR;
+}
 
-   /*
-    * Call device driver function.
-    */
-   if (ctx->Driver.DrawBuffers)
-      ctx->Driver.DrawBuffers(ctx, n, buffers);
-   else if (ctx->Driver.DrawBuffer)
-      ctx->Driver.DrawBuffer(ctx, buffers[0]);
+
+/**
+ * Like \sa _mesa_drawbuffers(), this is a helper function for setting
+ * GL_READ_BUFFER state in the context and current FBO.
+ * \param ctx  the rendering context
+ * \param buffer  GL_FRONT, GL_BACK, GL_COLOR_ATTACHMENT0, etc.
+ * \param bufferIndex  the numerical index corresponding to 'buffer'
+ */
+void
+_mesa_readbuffer(GLcontext *ctx, GLenum buffer, GLint bufferIndex)
+{
+   struct gl_framebuffer *fb = ctx->ReadBuffer;
+
+   if (fb->Name == 0) {
+      /* Only update the per-context READ_BUFFER state if we're bound to
+       * a window-system framebuffer.
+       */
+      ctx->Pixel.ReadBuffer = buffer;
+   }
+
+   fb->ColorReadBuffer = buffer;
+   fb->_ColorReadBufferIndex = bufferIndex;
+
+   ctx->NewState |= _NEW_PIXEL;
 }
 
 
@@ -534,6 +590,9 @@ _mesa_ReadBuffer(GLenum buffer)
    GET_CURRENT_CONTEXT(ctx);
    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);
 
+   if (MESA_VERBOSE & VERBOSE_API)
+      _mesa_debug(ctx, "glReadBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
+
    fb = ctx->ReadBuffer;
 
    if (MESA_VERBOSE & VERBOSE_API)
@@ -547,23 +606,21 @@ _mesa_ReadBuffer(GLenum buffer)
       /* general case / window-system framebuffer */
       srcBuffer = read_buffer_enum_to_index(buffer);
       if (srcBuffer == -1) {
-         _mesa_error(ctx, GL_INVALID_ENUM, "glReadBuffer(buffer=0x%x)", buffer);
+         _mesa_error(ctx, GL_INVALID_ENUM,
+                     "glReadBuffer(buffer=0x%x)", buffer);
          return;
       }
       supportedMask = supported_buffer_bitmask(ctx, fb);
       if (((1 << srcBuffer) & supportedMask) == 0) {
-         _mesa_error(ctx, GL_INVALID_OPERATION, "glReadBuffer(buffer=0x%x)", buffer);
+         _mesa_error(ctx, GL_INVALID_OPERATION,
+                     "glReadBuffer(buffer=0x%x)", buffer);
          return;
       }
    }
 
-   if (fb->Name == 0) {
-      ctx->Pixel.ReadBuffer = buffer;
-   }
-   fb->ColorReadBuffer = buffer;
-   fb->_ColorReadBufferIndex = srcBuffer;
+   /* OK, all error checking has been completed now */
 
-   ctx->NewState |= _NEW_PIXEL;
+   _mesa_readbuffer(ctx, buffer, srcBuffer);
 
    /*
     * Call device driver function.