Summary:
Remove layout-only views. Works by checking properties against a list of known properties that only affect layout. The `RCTShadowView` hierarchy still has a 1:1 correlation with the JS nodes.
This works by adjusting the tags and indices in `manageChildren`. For example, if JS told us to insert tag 1 at index 0 and tag 1 is layout-only with children whose tags are 2 and 3, we adjust it so we insert tags 2 and 3 at indices 0 and 1. This keeps changes out of `RCTView` and `RCTScrollView`. In order to simplify this logic, view moves are now processed as view removals followed by additions. A move from index 0 to 1 is recorded as a removal of view at indices 0 and 1 and an insertion of tags 1 and 2 at indices 0 and 1. Of course, the remaining indices have to be offset to take account for this.
The `collapsible` attribute is a bit of a hack to force `RCTScrollView` to always have one child. This was easier than rethinking out the logic there, but we could change this later.
Summary:
Remove layout-only views. Works by checking properties against a list of known properties that only affect layout. The `RCTShadowView` hierarchy still has a 1:1 correlation with the JS nodes.
This works by adjusting the tags and indices in `manageChildren`. For example, if JS told us to insert tag 1 at index 0 and tag 1 is layout-only with children whose tags are 2 and 3, we adjust it so we insert tags 2 and 3 at indices 0 and 1. This keeps changes out of `RCTView` and `RCTScrollView`. In order to simplify this logic, view moves are now processed as view removals followed by additions. A move from index 0 to 1 is recorded as a removal of view at indices 0 and 1 and an insertion of tags 1 and 2 at indices 0 and 1. Of course, the remaining indices have to be offset to take account for this.
The `collapsible` attribute is a bit of a hack to force `RCTScrollView` to always have one child. This was easier than rethinking out the logic there, but we could change this later.
@public
Test Plan: There are tests in `RCTUIManagerTests.m` that test the tag- and index-manipulation logic works. There are various scenarios including add-only, remove-only, and move. In addition, two scenario tests verify that the optimization works by checking the number of views and shadow views after various situations happen.
Andy Street
Dorota Kapturkiewicz
James Ide
Philipp von Weitershausen
Spencer Ahrens
Alex Akers
chaceliang
Georgiy Kassabli
Krzysztof Magiera