Summary:
With Nodes, we want to support recursive clipping of subviews.
Without this, surfaces like Marketplace won't properly handle subviews.
Reviewed By: sriramramani
Differential Revision: D3904721
Summary:
This fixes a crash for the case when we try to drop a view that has already been dropped.
**The Problem**
We got reports of a crash (t12912526) that occurs when the resolveViewManager method can't resolve a ViewManager for a View being dropped.
Investigating this, one thing in common between all the stack traces for this is that dropView is called from line 210 of FlatNativeViewHierarchyManager. This part of the code is specifically the part we added to remove strong references to any clipped children (from views that have subview clipping enabled).
So this is a problem specifically with Nodes and clipSubviews, which brings up some questions:
**when can this happen?**
The only situation this can possibly happen is when we drop a child (which is clipped) followed by dropping its parent in the same cycle. Consider a tree where each view only has one child, such as: A - B - C - D. This crash would happen if D is clipped, and we removed it, followed by removing any of its parents in the same frame.
**if the removes happen in different frames, does this bug occur?**
No - the reason is that before we execute the DropView operations, we run through StateBuilder, which traverses the shadow tree and marks updates, thus removing the view going away (such that the delete in the next frame doesn't try to re-delete it).
So why doesn't this happen when we're dropping in the same frame? The reason is that manageChildren (where this all starts) asks to remove some views. We handle this by removing said Nodes and their children from the shadow tree. Consequently, when StateBuilder iterates over the shadow tree, it can't do the right thing because said nodes no longer exist.
As a more concrete example, consider A - B - C - D again, and consider that both D and B are removed. StateBuilder only sees A, and realizes that it now has 0 children (whereas before it has 1), so it removes B from its children. However, this process isn't recursive, so C never gets cleaned up.
**why doesn't this happen with Nodes without clipping containers?**
The answer to this is that NativeViewHierarchyManager's dropView method checks the existance of each child before deeply dropping that child and its subtree. So in this case, we drop D and all its children, and when we come to drop B, we try to drop C (which exists) and then its children (D, which doesn't exist because we already dropped it, so we ignore it).
**why doesn't this happen with non-Nodes?**
The reason is that non-Nodes handles removes differently - every remove is enqueued in a call to NativeViewHierarchy's manageChildren, which explicitly asks the parent to remove said child. Consequently, we never try to remove a child that is already removed.
**Fix**
The initial fix was to check whether or not the view exists, but this updated patch just does the right thing at drop time - i.e. whenever a view is dropped, we notify the parent of this fact so that it can clear the reference from clipped views.
**One last Note**
There are two reasons for switching `super.dropView` to `dropView` - first, the comment is only partially correct - calling `super.dropView` will avoid looking at clipped children (as an aside, that could cause a leak in the case of nested clipping subviews), but will look at clipped grandchildren, because of the super class's iteration across the set of children.
Reviewed By: astreet
Differential Revision: D3815485
Summary:
@public
This is to be able to depend on ReactClippingViewGroup from BaseViewManager. Devs using ReactClippingViewGroup may need to update their imports when updating past this commit.
Reviewed By: lexs
Differential Revision: D3835328
Summary:
This is minor, but for our use case a SparseArray is going to be faster as long as we have less than 10,000 clipped subviews, and will also use much less memory.
Faster because of the boxing, unboxing and hash caching; less memory as it is two arrays instead of the object overhead of the HashMap.
Reviewed By: ahmedre
Differential Revision: D3704326
Summary: Adds support for horizontal clipping, though the FlatViewGroup needs to be made aware still of which it is.
Reviewed By: ahmedre
Differential Revision: D3673501
Summary: This optimizes node region searches in clipping cases, and does position calculation for drawCommands off of the UI thread.
Reviewed By: ahmedre
Differential Revision: D3665301
Summary: Add directional aware clipping to DrawCommandManager. Currently not attached to FlatViewGroup logic, with the plan to keep this unattached until we are clipping the way we want to in the final state.
Reviewed By: ahmedre
Differential Revision: D3622253
Summary: Previously, we had no information about the positioning of the view until after we had attached it. We have the position information attached to the shadow node, but this attaches it to the DrawView as well. It also removes the need for AbstractClippingDrawCommand.
Reviewed By: ahmedre
Differential Revision: D3609092
