refactor(ios): update paragraph spacing logic to handle marginTop correctly (#106)

Author: hryhoriiK97

ios/renderer/HeadingRenderer.m

@@ -72,9 +72,10 @@ - (void)renderNode:(MarkdownASTNode *)node into:(NSMutableAttributedString *)out
   applyLineHeight(output, range, style.lineHeight);
   applyTextAlignment(output, range, style.textAlign);
 
-  // Use paragraphSpacingBefore for internal elements; applyBlockSpacingBefore handles index 0
+  // Skip marginTop for the first block — already handled by applyBlockSpacingBefore above
   if (contentStart != 1) {
-    applyParagraphSpacingBefore(output, range, style.marginTop);
+    NSUInteger inserted = applyParagraphSpacingBefore(output, range, style.marginTop);
+    start += inserted;
   }
   applyParagraphSpacingAfter(output, start, style.marginBottom);
 }

ios/renderer/ParagraphRenderer.m

@@ -65,9 +65,10 @@ - (void)renderNode:(MarkdownASTNode *)node into:(NSMutableAttributedString *)out
 
   applyTextAlignment(output, range, _config.paragraphTextAlign);
 
-  // Apply marginTop for non-index-0 elements using paragraphSpacingBefore
+  // Skip marginTop for the first block — already handled by applyBlockSpacingBefore above
   if (shouldApplyMargin && contentStart != 1) {
-    applyParagraphSpacingBefore(output, range, marginTop);
+    NSUInteger inserted = applyParagraphSpacingBefore(output, range, marginTop);
+    start += inserted;
   }
 
   CGFloat marginBottom = 0;

ios/utils/ParagraphStyleUtils.h

@@ -10,7 +10,7 @@ extern NSAttributedString *kNewlineAttributedString;
 NSWritingDirection currentWritingDirection(void);
 NSMutableParagraphStyle *getOrCreateParagraphStyle(NSMutableAttributedString *output, NSUInteger index);
 void applyParagraphSpacingAfter(NSMutableAttributedString *output, NSUInteger start, CGFloat marginBottom);
-void applyParagraphSpacingBefore(NSMutableAttributedString *output, NSRange range, CGFloat marginTop);
+NSUInteger applyParagraphSpacingBefore(NSMutableAttributedString *output, NSRange range, CGFloat marginTop);
 NSUInteger applyBlockSpacingBefore(NSMutableAttributedString *output, NSUInteger insertionPoint, CGFloat marginTop);
 void applyBlockSpacingAfter(NSMutableAttributedString *output, CGFloat marginBottom);
 void applyLineHeight(NSMutableAttributedString *output, NSRange range, CGFloat lineHeight);

ios/utils/ParagraphStyleUtils.m

@@ -39,17 +39,32 @@ void applyParagraphSpacingAfter(NSMutableAttributedString *output, NSUInteger st
   [output addAttribute:NSParagraphStyleAttributeName value:style range:range];
 }
 
-void applyParagraphSpacingBefore(NSMutableAttributedString *output, NSRange range, CGFloat marginTop)
+NSUInteger applyParagraphSpacingBefore(NSMutableAttributedString *output, NSRange range, CGFloat marginTop)
 {
-  if (marginTop <= 0) {
-    return;
-  }
+  if (marginTop <= 0 || range.location == 0)
+    return 0;
 
-  // Note: paragraphSpacingBefore does not work at index 0 in TextKit.
-  // Leading spacing for the first element is handled by renderers via applyBlockSpacingBefore.
-  NSMutableParagraphStyle *style = getOrCreateParagraphStyle(output, range.location);
-  style.paragraphSpacingBefore = marginTop;
-  [output addAttribute:NSParagraphStyleAttributeName value:style range:range];
+  NSUInteger prevIdx = range.location - 1;
+  if ([output.string characterAtIndex:prevIdx] != '\n')
+    return 0;
+
+  NSParagraphStyle *prevStyle = [output attribute:NSParagraphStyleAttributeName atIndex:prevIdx effectiveRange:NULL];
+
+  CGFloat prevMarginBottom = prevStyle.paragraphSpacing;
+  if (prevMarginBottom >= marginTop)
+    return 0;
+
+  CGFloat extraGap = marginTop - prevMarginBottom;
+
+  NSMutableParagraphStyle *spacerStyle = [kBlockSpacerTemplate mutableCopy];
+  spacerStyle.baseWritingDirection = currentWritingDirection();
+  spacerStyle.paragraphSpacing = MAX(0, extraGap - 1.0);
+
+  NSDictionary *attrs = @{NSParagraphStyleAttributeName : spacerStyle};
+  NSAttributedString *spacer = [[NSAttributedString alloc] initWithString:@"\n" attributes:attrs];
+
+  [output insertAttributedString:spacer atIndex:range.location];
+  return 1;
 }
 
 NSUInteger applyBlockSpacingBefore(NSMutableAttributedString *output, NSUInteger insertionPoint, CGFloat marginTop)