+ if (last_prim->begin == 0) {
+ /* We're dealing with the second or later section of a split/wrapped
+ * GL_LINE_LOOP. Since we're converting line loops to line strips,
+ * we've already increment the last_prim->start counter by one to
+ * skip the 0th vertex in the loop. We need to undo that (effectively
+ * subtract one from last_prim->start) so that we copy the 0th vertex
+ * to the next vertex buffer.
+ */
+ assert(last_prim->start > 0);
+ src -= sz;
+ }
+ /* fall-through */