滚动条能加箭头吗？没有箭头，无法使用FastStone Capture滚动截屏！

编辑器上的滚动条没有箭头，不能使用FastStone Capture 截长屏。 箭头应该是标配的哟

Start by locating the editor scrollbar implementation and reproduce the missing-arrow behavior with FastStone Capture. Confirm the desired platform behavior and test scrolling screenshots with the arrows present; the work is done when the scrollbar displays usable arrow controls and FastStone Capture can capture the full editor content.

Written by the indexing model from the issue text.