Import Brian's drawbuffers fix from trunk version 1.108 of this file.

1 files changed, 29 insertions, 12 deletions

diff --git a/src/mesa/main/attrib.c b/src/mesa/main/attrib.c
index 4afd982314c..ef9b539ff31 100644
--- a/src/mesa/main/attrib.c
+++ b/src/mesa/main/attrib.c
@@ -848,18 +848,35 @@ _mesa_PopAttrib(void)
                                (GLboolean) (color->ColorMask[1] != 0),
                                (GLboolean) (color->ColorMask[2] != 0),
                                (GLboolean) (color->ColorMask[3] != 0));
-               /* Call the API_level functions, not _mesa_drawbuffers() since
-                * we need to do error checking on the pop'd GL_DRAW_BUFFER.
-                * Ex: if GL_FRONT were pushed, but we're popping with a user
-                * FBO bound, GL_FRONT will be illegal and we'll need to
-                * record that error.  Per OpenGL ARB decision.
-                */
-               if (ctx->Extensions.ARB_draw_buffers) {
-                  _mesa_DrawBuffersARB(ctx->Const.MaxDrawBuffers,
-                                       color->DrawBuffer);
-               }
-               else {
-                  _mesa_DrawBuffer(color->DrawBuffer[0]);
+               {
+                  /* Need to determine if more than one color output is
+                   * specified.  If so, call glDrawBuffersARB, else call
+                   * glDrawBuffer().  This is a subtle, but essential point
+                   * since GL_FRONT (for example) is illegal for the former
+                   * function, but legal for the later.
+                   */
+                  GLboolean multipleBuffers = GL_FALSE;
+                  if (ctx->Extensions.ARB_draw_buffers) {
+                     GLuint i;
+                     for (i = 1; i < ctx->Const.MaxDrawBuffers; i++) {
+                        if (color->DrawBuffer[i] != GL_NONE) {
+                           multipleBuffers = GL_TRUE;
+                           break;
+                        }
+                     }
+                  }
+                  /* Call the API_level functions, not _mesa_drawbuffers()
+                   * since we need to do error checking on the pop'd
+                   * GL_DRAW_BUFFER.
+                   * Ex: if GL_FRONT were pushed, but we're popping with a
+                   * user FBO bound, GL_FRONT will be illegal and we'll need
+                   * to record that error.  Per OpenGL ARB decision.
+                   */
+                  if (multipleBuffers)
+                     _mesa_DrawBuffersARB(ctx->Const.MaxDrawBuffers,
+                                          color->DrawBuffer);
+                  else
+                     _mesa_DrawBuffer(color->DrawBuffer[0]);
                }
                _mesa_set_enable(ctx, GL_ALPHA_TEST, color->AlphaEnabled);
                _mesa_AlphaFunc(color->AlphaFunc, color->AlphaRef);