Masonry scroll handler relies on event.target instead of event.currentTarget

[chinmaychaudhary]

Example: https://codesandbox.io/s/masonry-scroll-bug-e5vsd

On scrolling the red bordered div, everything is fine. When scrolling any of the inner divs i.e. the colored blocks, the onScroll for Masonry is invoked. The scroll handler of Masonry then looks at event.target (

react-virtualized/source/Masonry/Masonry.js

Line 413 in 710fc67

const eventScrollTop = event.target.scrollTop;

) instead of event.currentTarget which leads to incorrect behavior.

What is the current behavior?

If there's any scroll which is propagated to Masonry's div, the scrollTop is calculated using event.target instead of event.currentTarget (

react-virtualized/source/Masonry/Masonry.js

Line 413 in 710fc67

const eventScrollTop = event.target.scrollTop;

)

What is the expected behavior?

The scroll handler should look at the scrollTop of event.currentTarget

Which versions of React and react-virtualized, and which browser / OS are affected by this issue? Did this work in previous versions of react-virtualized?

Browser : Chrome
OS : MacOS
React : 16.9.0
React DOM : 16.9.0
react-virtualized : 9.21.1