5.0新增api对应4.0的getXY

主要用于给某一些x的特定位置（比如max、min）添加标注。目前设置text要么是data要么是x y的百分比像素，无法做到对应的功能。

Compare the 4.0 getXY API with the corresponding 5.0 API and inspect how text positions are currently specified. Determine how annotations at data locations such as max or min should be represented, then verify that the selected position is supported without relying only on data values or percentage-based pixel coordinates.

Written by the indexing model from the issue text.