- vbo->draw_prims( ctx, exec->array.inputs, prim, 1, &ib, ib.rebase, end+1 );
-}
+ /* Need to give special consideration to rendering a range of
+ * indices starting somewhere above zero. Typically the
+ * application is issuing multiple DrawRangeElements() to draw
+ * successive primitives layed out linearly in the vertex arrays.
+ * Unless the vertex arrays are all in a VBO (or locked as with
+ * CVA), the OpenGL semantics imply that we need to re-read or
+ * re-upload the vertex data on each draw call.
+ *
+ * In the case of hardware tnl, we want to avoid starting the
+ * upload at zero, as it will mean every draw call uploads an
+ * increasing amount of not-used vertex data. Worse - in the
+ * software tnl module, all those vertices might be transformed and
+ * lit but never rendered.
+ *
+ * If we just upload or transform the vertices in start..end,
+ * however, the indices will be incorrect.
+ *
+ * At this level, we don't know exactly what the requirements of
+ * the backend are going to be, though it will likely boil down to
+ * either:
+ *
+ * 1) Do nothing, everything is in a VBO and is processed once
+ * only.
+ *
+ * 2) Adjust the indices and vertex arrays so that start becomes
+ * zero.
+ *
+ * Rather than doing anything here, I'll provide a helper function
+ * for the latter case elsewhere.
+ */