Jony

I put the source file to `main.cpp`, and compile with `gcc -pthread main.cpp -o test`, no error happens. So there is no libraries missing in my environment, but there could...

Wow, your suggestion works. The real case is as follows, I reduced the document from thousands lines to one hundred lines. [test.zip](https://github.com/asciidocfx/AsciidocFX/files/5420714/test.zip)  Vertically, H4 aligns with H3, and H5...