Shuffle & Cleanup Stuff (#3080)

Source/TextKit/ASTextKitContext.h

@@ -0,0 +1,47 @@
+//
+//  ASTextKitContext.h
+//  AsyncDisplayKit
+//
+//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+//
+
+#import <UIKit/UIKit.h>
+#import <AsyncDisplayKit/ASBaseDefines.h>
+
+/**
+ A threadsafe container for the TextKit components that ASTextKit uses to lay out and truncate its text.
+
+ This container is the sole owner and manager of the TextKit classes.  This is an important model because of major
+ thread safety issues inside vanilla TextKit.  It provides a central locking location for accessing TextKit methods.
+ */
+AS_SUBCLASSING_RESTRICTED
+@interface ASTextKitContext : NSObject
+
+/**
+ Initializes a context and its associated TextKit components.
+
+ Initialization of TextKit components is a globally locking operation so be careful of bottlenecks with this class.
+ */
+- (instancetype)initWithAttributedString:(NSAttributedString *)attributedString
+                           lineBreakMode:(NSLineBreakMode)lineBreakMode
+                    maximumNumberOfLines:(NSUInteger)maximumNumberOfLines
+                          exclusionPaths:(NSArray *)exclusionPaths
+                         constrainedSize:(CGSize)constrainedSize;
+
+/**
+ All operations on TextKit values MUST occur within this locked context.  Simultaneous access (even non-mutative) to
+ TextKit components may cause crashes.
+
+ The block provided MUST not call out to client code from within its scope or it is possible for this to cause deadlocks
+ in your application.  Use with EXTREME care.
+
+ Callers MUST NOT keep a ref to these internal objects and use them later.  This WILL cause crashes in your application.
+ */
+- (void)performBlockWithLockedTextKitComponents:(AS_NOESCAPE void (^)(NSLayoutManager *layoutManager,
+                                                          NSTextStorage *textStorage,
+                                                          NSTextContainer *textContainer))block;
+
+@end