Initial timeline HTML support.

2026-11-03 16:10:20 +00:00 · 2022-03-24 14:47:55 +02:00
parent d3588cf6f1
commit cf42d61d27
20 changed files with 683 additions and 51 deletions
@@ -0,0 +1,200 @@
+//
+//  AttributedStringBuilderUtils.m
+//  ElementX
+//
+//  Created by Stefan Ceriu on 23/03/2022.
+//  Copyright © 2022 Element. All rights reserved.
+//
+
+#import "AttributedStringBuilderUtils.h"
+@import DTCoreText;
+
+// Temporary background color used to identify blockquote blocks with DTCoreText.
+#define kMXKToolsBlockquoteMarkColor [UIColor magentaColor]
+
+// Attribute in an NSAttributeString that marks a blockquote block that was in the original HTML string.
+NSString *const kMXKToolsBlockquoteMarkAttribute = @"kMXKToolsBlockquoteMarkAttribute";
+
+@implementation AttributedStringBuilderUtils
+
+ (NSAttributedString *)removeDTCoreTextArtifacts:(NSAttributedString *)attributedString
+{
+    NSMutableAttributedString *mutableAttributedString = [[NSMutableAttributedString alloc] initWithAttributedString:attributedString];
+    
+    // DTCoreText adds a newline at the end of plain text ( https://github.com/Cocoanetics/DTCoreText/issues/779 )
+    // or after a blockquote section.
+    // Trim trailing whitespace and newlines in the string content
+    while ([mutableAttributedString.string hasSuffixCharacterFromSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]])
+    {
+        [mutableAttributedString deleteCharactersInRange:NSMakeRange(mutableAttributedString.length - 1, 1)];
+    }
+    
+    // New lines may have also been introduced by the paragraph style
+    // Make sure the last paragraph style has no spacing
+    [mutableAttributedString enumerateAttributesInRange:NSMakeRange(0, mutableAttributedString.length) options:(NSAttributedStringEnumerationReverse) usingBlock:^(NSDictionary *attrs, NSRange range, BOOL *stop) {
+        
+        if (attrs[NSParagraphStyleAttributeName])
+        {
+            NSString *subString = [mutableAttributedString.string substringWithRange:range];
+            NSArray *components = [subString componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];
+            
+            NSMutableDictionary *updatedAttrs = [NSMutableDictionary dictionaryWithDictionary:attrs];
+            NSMutableParagraphStyle *paragraphStyle = [updatedAttrs[NSParagraphStyleAttributeName] mutableCopy];
+            paragraphStyle.paragraphSpacing = 0;
+            updatedAttrs[NSParagraphStyleAttributeName] = paragraphStyle;
+            
+            if (components.count > 1)
+            {
+                NSString *lastComponent = components.lastObject;
+                
+                NSRange range2 = NSMakeRange(range.location, range.length - lastComponent.length);
+                [mutableAttributedString setAttributes:attrs range:range2];
+                
+                range2 = NSMakeRange(range2.location + range2.length, lastComponent.length);
+                [mutableAttributedString setAttributes:updatedAttrs range:range2];
+            }
+            else
+            {
+                [mutableAttributedString setAttributes:updatedAttrs range:range];
+            }
+        }
+        
+        // Check only the last paragraph
+        *stop = YES;
+    }];
+    
+    // Image rendering failed on an exception until we replace the DTImageTextAttachments with a simple NSTextAttachment subclass
+    // (thanks to https://github.com/Cocoanetics/DTCoreText/issues/863).
+    [mutableAttributedString enumerateAttribute:NSAttachmentAttributeName
+                                        inRange:NSMakeRange(0, mutableAttributedString.length)
+                                        options:0
+                                     usingBlock:^(id value, NSRange range, BOOL *stop) {
+                                         
+                                         if ([value isKindOfClass:DTImageTextAttachment.class])
+                                         {
+                                             DTImageTextAttachment *attachment = (DTImageTextAttachment*)value;
+                                             NSTextAttachment *textAttachment = [[NSTextAttachment alloc] init];
+                                             if (attachment.image)
+                                             {
+                                                 textAttachment.image = attachment.image;
+                                                 
+                                                 CGRect frame = textAttachment.bounds;
+                                                 frame.size = attachment.displaySize;
+                                                 textAttachment.bounds = frame;
+                                             }
+                                             // Note we remove here attachment without image.
+                                             NSAttributedString *attrStringWithImage = [NSAttributedString attributedStringWithAttachment:textAttachment];
+                                             [mutableAttributedString replaceCharactersInRange:range withAttributedString:attrStringWithImage];
+                                         }
+                                     }];
+    
+    return mutableAttributedString;
+}
+
+ (NSString*)cssToMarkBlockquotes
+{
+    return [NSString stringWithFormat:@"blockquote {background: #%lX; display: block;}", (unsigned long)[[self class] rgbValueWithColor:kMXKToolsBlockquoteMarkColor]];
+}
+
+ (NSAttributedString*)removeMarkedBlockquotesArtifacts:(NSAttributedString*)attributedString
+{
+    NSMutableAttributedString *mutableAttributedString = [[NSMutableAttributedString alloc] initWithAttributedString:attributedString];
+
+    // Enumerate all sections marked thanks to `cssToMarkBlockquotes`
+    // and apply our own attribute instead.
+
+    // According to blockquotes in the string, DTCoreText can apply 2 policies:
+    //     - define a `DTTextBlocksAttribute` attribute on a <blockquote> block
+    //     - or, just define a `NSBackgroundColorAttributeName` attribute
+
+    // `DTTextBlocksAttribute` case
+    [attributedString enumerateAttribute:DTTextBlocksAttribute
+                                 inRange:NSMakeRange(0, attributedString.length)
+                                 options:0
+                              usingBlock:^(id  _Nullable value, NSRange range, BOOL * _Nonnull stop)
+     {
+         if ([value isKindOfClass:NSArray.class])
+         {
+             NSArray *array = (NSArray*)value;
+             if (array.count > 0 && [array[0] isKindOfClass:DTTextBlock.class])
+             {
+                 DTTextBlock *dtTextBlock = (DTTextBlock *)array[0];
+                 if ([dtTextBlock.backgroundColor isEqual:kMXKToolsBlockquoteMarkColor])
+                 {
+                     // Apply our own attribute
+                     [mutableAttributedString addAttribute:kMXKToolsBlockquoteMarkAttribute value:@(YES) range:range];
+
+                     // Fix a boring behaviour where DTCoreText add a " " string before a string corresponding
+                     // to an HTML blockquote. This " " string has ParagraphStyle.headIndent = 0 which breaks
+                     // the blockquote block indentation
+                     if (range.location > 0)
+                     {
+                         NSRange prevRange = NSMakeRange(range.location - 1, 1);
+
+                         NSRange effectiveRange;
+                         NSParagraphStyle *paragraphStyle = [attributedString attribute:NSParagraphStyleAttributeName
+                                                                                atIndex:prevRange.location
+                                                                         effectiveRange:&effectiveRange];
+
+                         // Check if this is the " " string
+                         if (paragraphStyle && effectiveRange.length == 1 && paragraphStyle.firstLineHeadIndent != 25)
+                         {
+                             // Fix its paragraph style
+                             NSMutableParagraphStyle *newParagraphStyle = [paragraphStyle mutableCopy];
+                             newParagraphStyle.firstLineHeadIndent = 25.0;
+                             newParagraphStyle.headIndent = 25.0;
+
+                             [mutableAttributedString addAttribute:NSParagraphStyleAttributeName value:newParagraphStyle range:prevRange];
+                         }
+                     }
+                 }
+             }
+         }
+     }];
+
+    // `NSBackgroundColorAttributeName` case
+    [mutableAttributedString enumerateAttribute:NSBackgroundColorAttributeName
+                                        inRange:NSMakeRange(0, mutableAttributedString.length)
+                                        options:0
+                                     usingBlock:^(id value, NSRange range, BOOL *stop)
+     {
+
+         if ([value isKindOfClass:UIColor.class] && [(UIColor*)value isEqual:kMXKToolsBlockquoteMarkColor])
+         {
+             // Remove the marked background
+             [mutableAttributedString removeAttribute:NSBackgroundColorAttributeName range:range];
+
+             // And apply our own attribute
+             [mutableAttributedString addAttribute:kMXKToolsBlockquoteMarkAttribute value:@(YES) range:range];
+         }
+     }];
+
+    return mutableAttributedString;
+}
+
+ (NSUInteger)rgbValueWithColor:(UIColor*)color
+{
+    CGFloat red, green, blue, alpha;
+    
+    [color getRed:&red green:&green blue:&blue alpha:&alpha];
+    
+    NSUInteger rgbValue = ((int)(red * 255) << 16) + ((int)(green * 255) << 8) + (blue * 255);
+    
+    return rgbValue;
+}
+
+ (void)enumerateMarkedBlockquotesInAttributedString:(NSAttributedString*)attributedString usingBlock:(void (^)(NSRange range, BOOL *stop))block
+{
+    [attributedString enumerateAttribute:kMXKToolsBlockquoteMarkAttribute
+                                 inRange:NSMakeRange(0, attributedString.length)
+                                 options:0
+                              usingBlock:^(id  _Nullable value, NSRange range, BOOL * _Nonnull stop)
+     {
+         if ([value isKindOfClass:NSNumber.class] && ((NSNumber*)value).boolValue)
+         {
+             block(range, stop);
+         }
+     }];
+}
+
+@end