ParagraphAttributesUtils.mm

#import "ParagraphAttributesUtils.h"
#import "EnrichedTextInputView.h"
#import "StyleHeaders.h"
#import "ParagraphsUtils.h"
#import "TextInsertionUtils.h"

@implementation ParagraphAttributesUtils

// if the user backspaces the last character in a line, the iOS applies typing attributes from the previous line
// in the case of some paragraph styles it works especially bad when a list point just appears
// hence the solution - reset typing attributes
+ (BOOL)handleBackspaceInRange:(NSRange)range replacementText:(NSString *)text input:(id)input {
  EnrichedTextInputView *typedInput = (EnrichedTextInputView *)input;
  UnorderedListStyle *ulStyle = typedInput->stylesDict[@([UnorderedListStyle getStyleType])];
  OrderedListStyle *olStyle = typedInput->stylesDict[@([OrderedListStyle getStyleType])];
  BlockQuoteStyle *bqStyle = typedInput->stylesDict[@([BlockQuoteStyle getStyleType])];
  
  if(typedInput == nullptr) {
    return NO;
  }
  
  // we make sure it was a backspace (text with 0 length) and it deleted something (range longer than 0)
  if(text.length > 0 || range.length == 0) {
    return NO;
  }
  
  // find a non-newline range of the paragraph
  NSRange paragraphRange = [typedInput->textView.textStorage.string paragraphRangeForRange:range];
  
  NSArray *paragraphs = [ParagraphsUtils getNonNewlineRangesIn:typedInput->textView range:paragraphRange];
  if(paragraphs.count == 0) {
    return NO;
  }
  
  NSRange nonNewlineRange = [(NSValue *)paragraphs.firstObject rangeValue];
  
  // if the backspace removes the whole content of a paragraph (possibly more but has to start where the paragraph starts), we remove the typing attributes
  if(range.location == nonNewlineRange.location && range.length >= nonNewlineRange.length) {
    // for lists and quotes we want to remove the characters but keep attribtues so that a zero width space appears here
    // so we do the removing manually and reapply attributes
    if([ulStyle detectStyle:nonNewlineRange]) {
      [TextInsertionUtils replaceText:text at:range additionalAttributes:nullptr input:typedInput withSelection:YES];
      [ulStyle addAttributes:NSMakeRange(range.location, 0)];
      return YES;
    }
    if([olStyle detectStyle:nonNewlineRange]) {
      [TextInsertionUtils replaceText:text at:range additionalAttributes:nullptr input:typedInput withSelection:YES];
      [olStyle addAttributes:NSMakeRange(range.location, 0)];
      return YES;
    }
    if([bqStyle detectStyle:nonNewlineRange]) {
      [TextInsertionUtils replaceText:text at:range additionalAttributes:nullptr input:typedInput withSelection:YES];
      [bqStyle addAttributes:NSMakeRange(range.location, 0)];
      return YES;
    }
  
    // do the replacement manually
    [TextInsertionUtils replaceText:text at:range additionalAttributes:nullptr input:typedInput withSelection:YES];
    // reset typing attribtues
    typedInput->textView.typingAttributes = typedInput->defaultTypingAttributes;
    return YES;
  }

  return NO;
}

@end