mirror of
https://github.com/facebook/react-native.git
synced 2025-11-01 09:14:26 +00:00
Valentin Shergin
28a5f122a8
Summary: MountingCoordinator is a borderline between Core and Mounting. Some of Core design constraints are impossible/impractical to enforce on Mounting layer, so we have to handle all of those cases in `MountingCoordinator`. One of the constrains is that all ShadowNodes implicitly depend on associated ComponentDescriptor instances without retaining them (retaining is expensive and creates a retain cycle). The problem is that the Mounting layer can call `MountingCoordinator::pull()` at any moment (even after the whole Core is already destroyed). To prevent this, the owner of a `MountingCoordinator` on the Core side calls `revoke()` right before being deallocated (right before the moment the owner cannot guarantee the constraint). Reviewed By: JoshuaGross Differential Revision: D17272295 fbshipit-source-id: ba8b02eab8f84cce68aa65c1ad36950cd2498049
143 lines
4.1 KiB
C++
143 lines
4.1 KiB
C++
/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <array>
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#include <cmath>
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#include <memory>
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#include <vector>
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#include <better/small_vector.h>
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#include <react/core/LayoutMetrics.h>
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#include <react/core/Sealable.h>
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#include <react/core/ShadowNode.h>
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#include <react/debug/DebugStringConvertible.h>
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#include <react/graphics/Transform.h>
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namespace facebook {
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namespace react {
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struct LayoutConstraints;
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struct LayoutContext;
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/*
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* Describes all sufficient layout API (in approach-agnostic way)
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* which makes a concurrent layout possible.
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*/
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class LayoutableShadowNode : public virtual Sealable {
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public:
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using UnsharedList = better::
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small_vector<LayoutableShadowNode *, kShadowNodeChildrenSmallVectorSize>;
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virtual ~LayoutableShadowNode() noexcept = default;
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/*
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* Measures the node (and node content, probably recursively) with
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* given constrains and relying on possible layout.
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* Default implementation returns zero size.
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*/
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virtual Size measure(LayoutConstraints layoutConstraints) const;
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/*
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* Computes layout recursively.
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* Additional environmental constraints might be provided via `layoutContext`
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* argument.
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* Default implementation basically calls `layoutChildren()` and then
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* `layout()` (recursively), and provides some obvious performance
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* optimization.
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*/
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virtual void layout(LayoutContext layoutContext);
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/*
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* Returns layout metrics computed during previous layout pass.
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*/
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virtual LayoutMetrics getLayoutMetrics() const;
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/*
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* Returns `true` if the node represents only information necessary for
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* layout computation and can be safely removed from view hierarchy.
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* Default implementation returns `false`.
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*/
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virtual bool isLayoutOnly() const;
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/*
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* Returns a transform object that represents transformations that will/should
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* be applied on top of regular layout metrics by mounting layer.
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* The `transform` value modifies a coordinate space of a layout system.
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* Default implementation returns `Identity` transform.
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*/
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virtual Transform getTransform() const;
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/*
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* Returns layout metrics relatively to the given ancestor node.
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*/
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LayoutMetrics getRelativeLayoutMetrics(
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const LayoutableShadowNode &ancestorLayoutableShadowNode) const;
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protected:
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/*
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* Clean or Dirty layout state:
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* Indicates whether all nodes (and possibly their subtrees) along the path
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* to the root node should be re-laid out.
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*/
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virtual void cleanLayout() = 0;
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virtual void dirtyLayout() = 0;
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virtual bool getIsLayoutClean() const = 0;
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/*
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* Indicates does the shadow node (or any descendand node of the node)
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* get a new layout metrics during a previous layout pass.
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*/
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virtual void setHasNewLayout(bool hasNewLayout) = 0;
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virtual bool getHasNewLayout() const = 0;
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/*
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* Applies layout for all children;
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* does not call anything in recursive manner *by desing*.
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*/
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virtual void layoutChildren(LayoutContext layoutContext);
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/*
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* Unifed methods to access text layout metrics.
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*/
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virtual Float firstBaseline(Size size) const;
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virtual Float lastBaseline(Size size) const;
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/*
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* Returns layoutable children to interate on.
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*/
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virtual LayoutableShadowNode::UnsharedList getLayoutableChildNodes()
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const = 0;
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/*
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* In case layout algorithm needs to mutate this (probably sealed) node,
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* it has to clone and replace it in the hierarchy before to do so.
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*/
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virtual LayoutableShadowNode *cloneAndReplaceChild(
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LayoutableShadowNode *child,
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int suggestedIndex = -1) = 0;
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/*
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* Sets layout metrics for the shadow node.
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* Returns true if the metrics are different from previous ones.
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*/
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virtual bool setLayoutMetrics(LayoutMetrics layoutMetrics);
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#pragma mark - DebugStringConvertible
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#if RN_DEBUG_STRING_CONVERTIBLE
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SharedDebugStringConvertibleList getDebugProps() const;
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#endif
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private:
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LayoutMetrics layoutMetrics_{};
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};
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} // namespace react
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} // namespace facebook
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