feat: [ScrollView,FlatList] Add ref.scrollToStart({animated?: boolean}) method

[retyui]

Summary:

scrollToEnd(options?: {animated?: boolean}) is available out of the box, and it's surprising that scrollToStart wasn't added yet

Changelog:

[GENERAL] [ADDED] - [ScrollView, FlatList] Add ref.scrollToStart({animated?: boolean}) method

Test Plan:

Manual + types tests

Android	iOS
Screen.Recording.2024-06-27.at.12.27.29.mov	Screen.Recording.2024-06-27.at.12.23.52.mov

[NickGerleman]

This seems like a sane addition, but current implementation is not correct for horizontal lists in RTL.

[retyui]

This seems like a sane addition, but current implementation is not correct for horizontal lists in RTL.

Let me create a demo and test it https://reactnative.dev/blog/2016/08/19/right-to-left-support-for-react-native-apps#making-an-app-rtl-ready

[NickGerleman]

The RNTester FlatList example has a checkbox for RTL which will apply forceRTL. That is what I usually use. But, the gist is that, as of recent versions, all the events and commands are aligned so that x coordinate space is not inverted.

This can be a bit tricky, since as more content is added to the list, the x coordinate will change alongside. scrollToIndex will try to find where the item is, but this will only works reliably in combination with getItemLayout.

scrollToEnd has some logic to do this based on metrics IIRC, but I think the reliable way to do this everywhere would be adding a scrollToStart native command.

[sammy-SC]

how does this behave if ScrollView has insets?