Summary:
It's just causing problems (e.g. when combined with transform animations like those used
in some navigators) and hopefully it's not necessary with JS-side windowing. If people need the
perf, they can turn it on themselves.
Should fix https://github.com/facebook/react-native/issues/13316 and related issues.
Reviewed By: achen1
Differential Revision: D4884147
fbshipit-source-id: 95c82448581076c0d0b2c80b1cd80cc294898174
Summary:
A nice bit of polish for apps is to update the separators between list items
when press actives the highlight (things get especially noticeable/ugly when
the separators are not full width and don't adjust). This can be difficult to
coordinate and update efficiently, so we bake the functionality into
`VirtualizedList`.
The approach taken here is a little different from `ListView`. We pass a new
`separators` object with `renderItem` that has easy-to-use callbacks for toggling
the 'highlighted' prop on both adjacent separators - they can be wired up
directly to the `onShow/HideUnderlay` props of `TouchableHighlight` (pit of
success and all that - we want those RN apps to be polished!), but we also
provide a more generic `separators.updateProps` method to set any custom
props. This also passes in `leadingItem` so more custom wiring can be done on
initial render (e.g. linking the highlight state with `Animated`).
This also moves the separator rendering into the `CellRenderer`. I think this might
also fix some subtle measurement bugs with the `onLayout` not capturing the
height of the separator, so that's nice too, but the main reason is to have
an easy place to store the state so we don't have to re-render the entire list
like `ListView` does. Instead we track references to the cells and call update
only on the two we care about so the feedback is instantaneous even with big,
heavy lists.
This diff also messes with a bunch of flow and updates the example to be more
like a standard list.
`SectionList` support is coming in a stacked diff.
**TestPlan**
Video demo:
https://youtu.be/uFE7qGA0mg4
Pretty sure this is backwards compatible....
Reviewed By: thechefchen
Differential Revision: D4833557
fbshipit-source-id: 685af46243ba13246bf280dae8a4223381ce8cea
Summary:
If tracking is enabled and the sampling check passes on a scroll or layout event,
we compare the scroll offset to the layout of the rendered items. If the items don't cover
the visible area of the list, we fire an `onFillRateExceeded` call with relevant stats for
logging the event through an analytics pipeline.
The measurement methodology is a little jank because everything is async, but it seems directionally
useful for getting ballpark numbers, catching regressions, and tracking improvements.
Benchmark testing shows a ~2014 MotoX starts hitting the fill rate limit at about 2500 px / sec,
which is pretty fast scrolling.
This also reworks our frame rate stuff so we can use a shared `SceneTracking` thing and track blankness
globally.
Reviewed By: bvaughn
Differential Revision: D4806867
fbshipit-source-id: 119bf177463c8c3aa51fa13d1a9d03b1a96042aa
