Fabric: ShadowTree::synchronize and reliable constraintLayout

Summary:
New `ShadowTree::synchronize` method allows to perform operations on ShadowTree without a risk of an unsuccessful commit. To make it happen, the `commitMutex_` is now recursive and `synchronize` acquires it before calling the callback.
Using that we finally can implement reliable `constraintLayout`.

Reviewed By: mdvacca

Differential Revision: D10174281

fbshipit-source-id: 9864ebb5343d40e2da205272a834710f0ab730db

React/Fabric/RCTScheduler.h

@@ -49,7 +49,7 @@ NS_ASSUME_NONNULL_BEGIN
                                 layoutContext:(facebook::react::LayoutContext)layoutContext
                                     surfaceId:(facebook::react::SurfaceId)surfaceId;
 
-- (BOOL)constraintSurfaceLayoutWithLayoutConstraints:(facebook::react::LayoutConstraints)layoutConstraints
+- (void)constraintSurfaceLayoutWithLayoutConstraints:(facebook::react::LayoutConstraints)layoutConstraints
                                        layoutContext:(facebook::react::LayoutContext)layoutContext
                                            surfaceId:(facebook::react::SurfaceId)surfaceId;
 

React/Fabric/RCTScheduler.mm

@@ -80,11 +80,11 @@ private:
   return RCTCGSizeFromSize(_scheduler->measureSurface(surfaceId, layoutConstraints, layoutContext));
 }
 
-- (BOOL)constraintSurfaceLayoutWithLayoutConstraints:(LayoutConstraints)layoutConstraints
+- (void)constraintSurfaceLayoutWithLayoutConstraints:(LayoutConstraints)layoutConstraints
                                        layoutContext:(LayoutContext)layoutContext
                                            surfaceId:(SurfaceId)surfaceId
 {
-  return _scheduler->constraintSurfaceLayout(surfaceId, layoutConstraints, layoutContext);
+  _scheduler->constraintSurfaceLayout(surfaceId, layoutConstraints, layoutContext);
 }
 
 @end

React/Fabric/RCTSurfacePresenter.h

@@ -57,9 +57,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 /**
  * Sets `minimumSize` and `maximumSize` layout constraints for the Surface.
- * Returns `YES` if the operation finished successfully.
  */
-- (BOOL)setMinimumSize:(CGSize)minimumSize
+- (void)setMinimumSize:(CGSize)minimumSize
            maximumSize:(CGSize)maximumSize
                surface:(RCTFabricSurface *)surface;
 

React/Fabric/RCTSurfacePresenter.mm

@@ -119,7 +119,7 @@ using namespace facebook::react;
                                                     surfaceId:surface.rootTag];
 }
 
-- (BOOL)setMinimumSize:(CGSize)minimumSize
+- (void)setMinimumSize:(CGSize)minimumSize
            maximumSize:(CGSize)maximumSize
                surface:(RCTFabricSurface *)surface
 {
@@ -129,9 +129,9 @@ using namespace facebook::react;
   layoutConstraints.minimumSize = RCTSizeFromCGSize(minimumSize);
   layoutConstraints.maximumSize = RCTSizeFromCGSize(maximumSize);
 
-  return [self._scheduler constraintSurfaceLayoutWithLayoutConstraints:layoutConstraints
-                                                         layoutContext:layoutContext
-                                                             surfaceId:surface.rootTag];
+  [self._scheduler constraintSurfaceLayoutWithLayoutConstraints:layoutConstraints
+                                                  layoutContext:layoutContext
+                                                      surfaceId:surface.rootTag];
 }
 
 #pragma mark - Private

ReactCommon/fabric/uimanager/Scheduler.cpp

@@ -94,7 +94,7 @@ Size Scheduler::measureSurface(
   return shadowTree->measure(layoutConstraints, layoutContext);
 }
 
-bool Scheduler::constraintSurfaceLayout(
+void Scheduler::constraintSurfaceLayout(
   SurfaceId surfaceId,
   const LayoutConstraints &layoutConstraints,
   const LayoutContext &layoutContext
@@ -102,7 +102,9 @@ bool Scheduler::constraintSurfaceLayout(
   std::lock_guard<std::mutex> lock(mutex_);
   const auto &shadowTree = shadowTreeRegistry_.at(surfaceId);
   assert(shadowTree);
-  return shadowTree->constraintLayout(layoutConstraints, layoutContext);
+  shadowTree->synchronize([&]() {
+    shadowTree->constraintLayout(layoutConstraints, layoutContext);
+  });
 }
 
 #pragma mark - Delegate

ReactCommon/fabric/uimanager/Scheduler.h

@@ -53,10 +53,9 @@ public:
    * The user interface will be relaid out as a result. The operation will be
    * performed synchronously (including mounting) if the method is called
    * on the main thread.
-   * Returns `true` if the operation finished successfully.
    * Can be called from any thread.
    */
-  bool constraintSurfaceLayout(
+  void constraintSurfaceLayout(
     SurfaceId surfaceId,
     const LayoutConstraints &layoutConstraints,
     const LayoutContext &layoutContext

ReactCommon/fabric/uimanager/ShadowTree.cpp

@@ -39,10 +39,15 @@ Tag ShadowTree::getRootTag() const {
 }
 
 SharedRootShadowNode ShadowTree::getRootShadowNode() const {
-  std::lock_guard<std::mutex> lock(commitMutex_);
+  std::lock_guard<std::recursive_mutex> lock(commitMutex_);
   return rootShadowNode_;
 }
 
+void ShadowTree::synchronize(std::function<void(void)> function) const {
+  std::lock_guard<std::recursive_mutex> lock(commitMutex_);
+  function();
+}
+
 #pragma mark - Layout
 
 Size ShadowTree::measure(const LayoutConstraints &layoutConstraints, const LayoutContext &layoutContext) const {
@@ -109,7 +114,7 @@ bool ShadowTree::commit(
   const SharedRootShadowNode &newRootShadowNode,
   const ShadowViewMutationList &mutations
 ) const {
-  std::lock_guard<std::mutex> lock(commitMutex_);
+  std::lock_guard<std::recursive_mutex> lock(commitMutex_);
 
   if (oldRootShadowNode != rootShadowNode_) {
     return false;

ReactCommon/fabric/uimanager/ShadowTree.h

@@ -38,6 +38,16 @@ public:
    */
   Tag getRootTag() const;
 
+  /*
+   * Synchronously runs `function` when `commitMutex_` is acquired.
+   * It is useful in cases when transactional consistency and/or successful
+   * commit are required. E.g. you might want to run `measure` and
+   * `constraintLayout` as part of a single congious transaction.
+   * Use this only if it is necessary. All public methods of the class are
+   * already thread-safe.
+   */
+  void synchronize(std::function<void(void)> function) const;
+
 #pragma mark - Layout
 
   /*
@@ -93,7 +103,7 @@ private:
   const Tag rootTag_;
   mutable SharedRootShadowNode rootShadowNode_; // Protected by `commitMutex_`.
   ShadowTreeDelegate const *delegate_;
-  mutable std::mutex commitMutex_;
+  mutable std::recursive_mutex commitMutex_;
 };
 
 } // namespace react