PuTTY 若是遇到軟體是用 alternate screen, 就不會把 buffer 加到 scrollback,
然而 screen 就是用 alternate screen, 所以 PuTTY+screen scrollback 會失效.
有兩種方式可以解決
1. 停用 PuTTY 的 alternate screen
Terminal / Features / Disable switching to alternate terminal screen
2. 停用 screen 的 alternate screen
加一行 termcapinfo xterm ti@:te@ 到 screenrc
ref. A.7.19 Since I upgraded to PuTTY 0.54, the scrollback has stopped working when I run screen.