1 files changed, 16 insertions, 17 deletions

diff --git a/src/mesa/main/buffers.c b/src/mesa/main/buffers.c
index b23d2f612b..d8b5f3b1f4 100644
--- a/src/mesa/main/buffers.c
+++ b/src/mesa/main/buffers.c
@@ -120,11 +120,9 @@ draw_buffer_enum_to_bitmask(GLenum buffer)
       case GL_AUX0:
          return BUFFER_BIT_AUX0;
       case GL_AUX1:
-         return BUFFER_BIT_AUX1;
       case GL_AUX2:
-         return BUFFER_BIT_AUX2;
       case GL_AUX3:
-         return BUFFER_BIT_AUX3;
+         return 1 << BUFFER_COUNT; /* invalid, but not BAD_MASK */
       case GL_COLOR_ATTACHMENT0_EXT:
          return BUFFER_BIT_COLOR0;
       case GL_COLOR_ATTACHMENT1_EXT:
@@ -177,11 +175,9 @@ read_buffer_enum_to_index(GLenum buffer)
       case GL_AUX0:
          return BUFFER_AUX0;
       case GL_AUX1:
-         return BUFFER_AUX1;
       case GL_AUX2:
-         return BUFFER_AUX2;
       case GL_AUX3:
-         return BUFFER_AUX3;
+         return BUFFER_COUNT; /* invalid, but not -1 */
       case GL_COLOR_ATTACHMENT0_EXT:
          return BUFFER_COLOR0;
       case GL_COLOR_ATTACHMENT1_EXT:
@@ -247,13 +243,14 @@ _mesa_DrawBuffer(GLenum buffer)
       destMask = draw_buffer_enum_to_bitmask(buffer);
       if (destMask == BAD_MASK) {
          /* totally bogus buffer */
-         _mesa_error(ctx, GL_INVALID_ENUM, "glDrawBuffer(buffer)");
+         _mesa_error(ctx, GL_INVALID_ENUM, "glDrawBuffer(buffer=0x%x)", buffer);
          return;
       }
       destMask &= supportedMask;
       if (destMask == 0x0) {
          /* none of the named color buffers exist! */
-         _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffer(buffer)");
+         _mesa_error(ctx, GL_INVALID_OPERATION,
+                     "glDrawBuffer(buffer=0x%x)", buffer);
          return;
       }
    }
@@ -289,11 +286,10 @@ _mesa_DrawBuffersARB(GLsizei n, const GLenum *buffers)
    GET_CURRENT_CONTEXT(ctx);
    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);
 
-   if (!ctx->Extensions.ARB_draw_buffers) {
-      _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffersARB");
-      return;
-   }
-   if (n < 1 || n > (GLsizei) ctx->Const.MaxDrawBuffers) {
+   /* Turns out n==0 is a valid input that should not produce an error.
+    * The remaining code below correctly handles the n==0 case.
+    */
+   if (n < 0 || n > (GLsizei) ctx->Const.MaxDrawBuffers) {
       _mesa_error(ctx, GL_INVALID_VALUE, "glDrawBuffersARB(n)");
       return;
    }
@@ -335,12 +331,14 @@ _mesa_DrawBuffersARB(GLsizei n, const GLenum *buffers)
    _mesa_drawbuffers(ctx, n, buffers, destMask);
 
    /*
-    * Call device driver function.
+    * Call device driver function.  Note that n can be equal to 0,
+    * in which case we don't want to reference buffers[0], which
+    * may not be valid.
     */
    if (ctx->Driver.DrawBuffers)
       ctx->Driver.DrawBuffers(ctx, n, buffers);
    else if (ctx->Driver.DrawBuffer)
-      ctx->Driver.DrawBuffer(ctx, buffers[0]);
+      ctx->Driver.DrawBuffer(ctx, n>0? buffers[0]:GL_NONE);
 }
 
 
@@ -419,7 +417,7 @@ _mesa_drawbuffers(GLcontext *ctx, GLuint n, const GLenum *buffers,
       }
    }
 
-   ctx->NewState |= _NEW_COLOR;
+   ctx->NewState |= _NEW_BUFFERS;
 }
 
 
@@ -445,7 +443,7 @@ _mesa_readbuffer(GLcontext *ctx, GLenum buffer, GLint bufferIndex)
    fb->ColorReadBuffer = buffer;
    fb->_ColorReadBufferIndex = bufferIndex;
 
-   ctx->NewState |= _NEW_PIXEL;
+   ctx->NewState |= _NEW_BUFFERS;
 }
 
 
@@ -494,6 +492,7 @@ _mesa_ReadBuffer(GLenum buffer)
    /* OK, all error checking has been completed now */
 
    _mesa_readbuffer(ctx, buffer, srcBuffer);
+   ctx->NewState |= _NEW_BUFFERS;
 
    /*
     * Call device driver function.