feature request: extend NO_SCROLLBAR with horizontal/vertical options

Sometimes a scrollbar can appear that has no effect because it scrolls 0px in that direction. The same is true for very small "scrollable distances" like a couple of pixels.

Thus it would be nice to be able to disable just one of the scrollbars and keep the other if the content inside is big enough to require it.

首先定位 NO_SCROLLBAR 的实现，以及确定水平和垂直可滚动距离的代码。检查当前在距离为零或非常小时如何生成滚动条。完成标准是支持独立禁用水平和垂直滚动，同时在另一个方向需要滚动条时保留该滚动条。

由索引模型根据 Issue 内容生成。