Add Experimental Text Node Implementation (#259)

* Add experimental text node implementation, based on YYText

* Fix warnings and alert when unimplemented experimental features are used.

* Address feedback from review

* Extend the cthulog

* Update license headers

Source/Private/TextExperiment/Component/ASTextDebugOption.h

@@ -0,0 +1,95 @@
+//
+//  ASTextDebugOption.h
+//  Modified from YYText <https://github.com/ibireme/YYText>
+//
+//  Created by ibireme on 15/4/8.
+//  Copyright (c) 2015 ibireme.
+//
+//  This source code is licensed under the MIT-style license found in the
+//  LICENSE file in the root directory of this source tree.
+//
+
+#import <UIKit/UIKit.h>
+
+@class ASTextDebugOption;
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ The ASTextDebugTarget protocol defines the method a debug target should implement.
+ A debug target can be add to the global container to receive the shared debug
+ option changed notification.
+ */
+@protocol ASTextDebugTarget <NSObject>
+
+@required
+/**
+ When the shared debug option changed, this method would be called on main thread.
+ It should return as quickly as possible. The option's property should not be changed
+ in this method.
+ 
+ @param option  The shared debug option.
+ */
+- (void)setDebugOption:(nullable ASTextDebugOption *)option;
+@end
+
+
+
+/**
+ The debug option for ASText.
+ */
+@interface ASTextDebugOption : NSObject <NSCopying>
+@property (nullable, nonatomic, strong) UIColor *baselineColor;      ///< baseline color
+@property (nullable, nonatomic, strong) UIColor *CTFrameBorderColor; ///< CTFrame path border color
+@property (nullable, nonatomic, strong) UIColor *CTFrameFillColor;   ///< CTFrame path fill color
+@property (nullable, nonatomic, strong) UIColor *CTLineBorderColor;  ///< CTLine bounds border color
+@property (nullable, nonatomic, strong) UIColor *CTLineFillColor;    ///< CTLine bounds fill color
+@property (nullable, nonatomic, strong) UIColor *CTLineNumberColor;  ///< CTLine line number color
+@property (nullable, nonatomic, strong) UIColor *CTRunBorderColor;   ///< CTRun bounds border color
+@property (nullable, nonatomic, strong) UIColor *CTRunFillColor;     ///< CTRun bounds fill color
+@property (nullable, nonatomic, strong) UIColor *CTRunNumberColor;   ///< CTRun number color
+@property (nullable, nonatomic, strong) UIColor *CGGlyphBorderColor; ///< CGGlyph bounds border color
+@property (nullable, nonatomic, strong) UIColor *CGGlyphFillColor;   ///< CGGlyph bounds fill color
+
+- (BOOL)needDrawDebug; ///< `YES`: at least one debug color is visible. `NO`: all debug color is invisible/nil.
+- (void)clear; ///< Set all debug color to nil.
+
+/**
+ Add a debug target.
+ 
+ @discussion When `setSharedDebugOption:` is called, all added debug target will
+ receive `setDebugOption:` in main thread. It maintains an unsafe_unretained
+ reference to this target. The target must to removed before dealloc.
+ 
+ @param target A debug target.
+ */
++ (void)addDebugTarget:(id<ASTextDebugTarget>)target;
+
+/**
+ Remove a debug target which is added by `addDebugTarget:`.
+ 
+ @param target A debug target.
+ */
++ (void)removeDebugTarget:(id<ASTextDebugTarget>)target;
+
+/**
+ Returns the shared debug option.
+ 
+ @return The shared debug option, default is nil.
+ */
++ (nullable ASTextDebugOption *)sharedDebugOption;
+
+/**
+ Set a debug option as shared debug option.
+ This method must be called on main thread.
+ 
+ @discussion When call this method, the new option will set to all debug target
+ which is added by `addDebugTarget:`.
+ 
+ @param option  A new debug option (nil is valid).
+ */
++ (void)setSharedDebugOption:(nullable ASTextDebugOption *)option;
+
+@end
+
+NS_ASSUME_NONNULL_END