Summary:
VirtualizedList state is represented in terms of [first, last] ranges, where it is possible to express a zero-cell range by having [n, n-1]. This includes some awkward examples, like [0, -1] being valid.
CellRenderMask assumes `addCells` is called with at least one cell, with VirtualizedList previously guarding against adding the no cell case. This guard is present for adding main cell regions, but not for `_initialRenderRegion()`, which can be overridden to have a zero length as well.
This moves the `CellRenderMask` to be permissive of zero-length cell regions, and removes the caller guard.
Changelog:
[Internal][Fixed] - Allow empty cell ranges in CellRenderMask
Reviewed By: rshest
Differential Revision: D38184444
fbshipit-source-id: d2dadfdd9628b24f894126d63b1eb93f6387b877
Summary:
A CellRenderMask helps track regions of cells/spacers to render. It's API allows adding ranges of cells, where its otput be an ordered list of contiguous spacer/non-spacer ranges.
The implementation keeps this region list internally, splitting or merging regions when cells are added. This output will be used by the render function of a refactored VirtualizedList.
## Changelog
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[Internal] [Added] - Add "CellRenderMask" Region Tracking Structure
Pull Request resolved: https://github.com/facebook/react-native/pull/31420
Test Plan: Validated via UTs.
Reviewed By: lunaleaps
Differential Revision: D28293161
Pulled By: rozele
fbshipit-source-id: a5e4e2144a90387aabe0974650429018440abf67
Nick Gerleman
Andres Suarez
Nick Gerleman