svga: fix zero-stride vertex array bug

For zero-stride vertex arrays, the svga driver copies the value into
the constant value and uses that value in the shader.  The recent
gallium-userbuf changes caused a regression in this.  An example
symptom was per-primitive glColor3f() calls getting ignored.

Where we copied the vertex value from the vertex buffer to the
constant buffer we neglected to take into account the
pipe_vertex_buffer::buffer_offset field.  Adding that value to the
source offset fixes the problem.  Actually, it looks like we should
have been doing this all along, but it never was an issue before for
some reason.

diff --git a/src/gallium/drivers/svga/svga_state_vs.c b/src/gallium/drivers/svga/svga_state_vs.c
index 3cb0cdb96979cd1fd5848ccd6ced5909143e57c1..1d140bd03a14143be6e080ec59e3a46ad5e4e092 100644 (file)
--- a/src/gallium/drivers/svga/svga_state_vs.c
+++ b/src/gallium/drivers/svga/svga_state_vs.c
@@ -222,7 +222,11 @@ struct svga_tracked_state svga_hw_vs =
 };
 
 
-/***********************************************************************
+/**
+ * This function handles the special case of vertex attributes
+ * with stride=0.  Basically, copy those values into the constant
+ * buffer and modify the vertex shader to get the values from the
+ * constant buffer rather than a vertex array.
  */
 static enum pipe_error
 update_zero_stride( struct svga_context *svga,
@@ -269,7 +273,7 @@ update_zero_stride( struct svga_context *svga,
          
          mapped_buffer = pipe_buffer_map_range(&svga->pipe, 
                                                vbuffer->buffer,
-                                               vel->src_offset,
+                                               vel->src_offset + vbuffer->buffer_offset,
                                                util_format_get_blocksize(vel->src_format),
                                                PIPE_TRANSFER_READ,
                                               &transfer);