SEP-491 prerequisite: add textViewShouldBeginEditing: to ASEditableTextNodeDelegate (#535)

* SEP-491 prerequisite: add textViewShouldBeginEditing: to ASEditableTextNodeDelegate

* - added entry to CHANGELOG.md, addressed nit

CHANGELOG.md

@@ -14,6 +14,7 @@
 - Fix retain cycle between ASImageNode and PINAnimatedImage [Phil Larson](https://github.com/plarson) [#520](https://github.com/TextureGroup/Texture/pull/520)
 - Change the API for disabling logging from a compiler flag to a runtime C function ASDisableLogging().  [Adlai Holler](https://github.com/Adlai-Holler) [#528](https://github.com/TextureGroup/Texture/pull/528)
 - Table and collection views to consider content inset when calculating (default) element size range [Huy Nguyen](https://github.com/nguyenhuy) [#525](https://github.com/TextureGroup/Texture/pull/525)
+- [ASEditableTextNode] added -editableTextNodeShouldBeginEditing to ASEditableTextNodeDelegate to mirror the corresponding method from UITextViewDelegate. [Yan S.](https://github.com/yans) [#535](https://github.com/TextureGroup/Texture/pull/535)
 
 ##2.4
 - Fix an issue where inserting/deleting sections could lead to inconsistent supplementary element behavior. [Adlai Holler](https://github.com/Adlai-Holler)

Source/ASEditableTextNode.h

@@ -158,6 +158,13 @@ NS_ASSUME_NONNULL_BEGIN
 @protocol ASEditableTextNodeDelegate <NSObject>
 
 @optional
+/**
+ @abstract Asks the delegate if editing should begin for the text node.
+ @param editableTextNode An editable text node.
+ @discussion YES if editing should begin; NO if editing should not begin -- the default returns YES.
+ */
+- (BOOL)editableTextNodeShouldBeginEditing:(ASEditableTextNode *)editableTextNode;
+
 /**
   @abstract Indicates to the delegate that the text node began editing.
   @param editableTextNode An editable text node.

Source/ASEditableTextNode.mm

@@ -699,6 +699,12 @@
 }
 
 #pragma mark - UITextView Delegate
+- (BOOL)textViewShouldBeginEditing:(UITextView *)textView
+{
+  // Delegateify.
+  return [self _delegateShouldBeginEditing];
+}
+
 - (void)textViewDidBeginEditing:(UITextView *)textView
 {
   // Delegateify.
@@ -793,6 +799,14 @@
 }
 
 #pragma mark -
+- (BOOL)_delegateShouldBeginEditing
+{
+  if ([_delegate respondsToSelector:@selector(editableTextNodeShouldBeginEditing:)]) {
+    return [_delegate editableTextNodeShouldBeginEditing:self];
+  }
+  return YES;
+}
+
 - (void)_delegateDidBeginEditing
 {
   if ([_delegate respondsToSelector:@selector(editableTextNodeDidBeginEditing:)])