ScrollView - only send the didScroll event if the document origin has changed

[shwanton]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary

• In 0.71, we had a race condition where the ScrollView scrollViewDocumentViewBoundsDidChange notification would sometimes trigger the onScroll event with a contentSize of zero.
• This happened when the scrollview was loading data & showing a spinner. With and empty contentSize, the spinner would be stuck and the content would never render.
• With this fix, we track the latest document view origin & we only emit the onScroll if the origin has changed which means scrolling has occurred.

Changelog

[MACOs] [FIXED] - ScrollView - only send the didScroll event if the document origin has changed

Test Plan

• This race condition was intermittent and I could not repro with RNTester using setTimeout to imitate the behavior of loading data.

Before (spinner gets stuck & content doesn't load)

CleanShot.2023-05-31.at.17.27.44.mp4

After

CleanShot.2023-05-31.at.17.34.10.mp4

[Saadnajmi]

Will this also come to main?

[shwanton]

Will this also come to main?

I originally had this only on main. Just changed the title so it's not referencing 0.71
Do you want me to pick this to 0.71 as well?

[Saadnajmi]

Will this also come to main?

I originally had this only on main. Just changed the title so it's not referencing 0.71
Do you want me to pick this to 0.71 as well?

Up to you if you want to pick to 0.71. I think we won't personally do it unless we run into the same bug.