draw/pt: adjust overflow calculations

gallium lies. buffer_size is not actually buffer_size but available
size, which is 'buffer_size - buffer_offset' so by adding buffer
offset we'd incorrectly compute overflow.

Signed-off-by: Zack Rusin <[email protected]>
Reviewed-by: José Fonseca <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/gallium/include/pipe/p_state.h b/src/gallium/include/pipe/p_state.h
index 28249d2261a..262078d09b3 100644
--- a/src/gallium/include/pipe/p_state.h
+++ b/src/gallium/include/pipe/p_state.h
@@ -465,6 +465,13 @@ struct pipe_constant_buffer {
  * have been written. The internal offset can be stored on the device
  * and the CPU actually doesn't have to query it.
  *
+ * Note that the buffer_size variable is actually specifying the available
+ * space in the buffer, not the size of the attached buffer. 
+ * In other words in majority of cases buffer_size would simply be 
+ * 'buffer->width0 - buffer_offset', so buffer_size refers to the size
+ * of the buffer left, after accounting for buffer offset, for stream output
+ * to write to.
+ *
  * Use PIPE_QUERY_SO_STATISTICS to know how many primitives have
  * actually been written.
  */