From d6019fdb8aa8c99ffec46130fb8e05d8acd72cad Mon Sep 17 00:00:00 2001
From: Matt Voska <voska@users.noreply.github.com>
Date: Thu, 1 Oct 2026 10:41:51 -0300
Subject: [PATCH] fix(ios): give each list item's marker array its own hash

Each list item stores its markers as an NSArray attribute value. NSArray's
-hash is its count, so every one-marker array hashes to 1, while the
descriptors inside compare by identity, so no two of those arrays are equal.
UIFoundation uniques attribute dictionaries in a hash table, so adding item
N's marker probes past every earlier item's dictionary: rendering is
quadratic in the number of list items, and memory grows with it.

Store the markers in an NSArray subclass whose -hash is the hash of the
item's own (last) marker. It is still an NSArray, so ListMarkerDrawer and
TaskListTapUtils read it unchanged, and arrays that are equal still hash
equal.
---
 .../ios/renderer/ListItemRenderer.m           | 39 ++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/packages/react-native-enriched-markdown/ios/renderer/ListItemRenderer.m b/packages/react-native-enriched-markdown/ios/renderer/ListItemRenderer.m
index 018014b63..cc554b2f6 100644
--- a/packages/react-native-enriched-markdown/ios/renderer/ListItemRenderer.m
+++ b/packages/react-native-enriched-markdown/ios/renderer/ListItemRenderer.m
@@ -19,6 +19,41 @@
 @implementation ENRMListMarkerDescriptor
 @end
 
+// NSArray's -hash is its count, so plain one-marker arrays all collide in the
+// table that uniques attribute dictionaries, and each list item probes past
+// every earlier one. Hashing by the item's own marker keeps rendering linear.
+@interface ENRMListMarkerArray : NSArray
+@end
+
+@implementation ENRMListMarkerArray {
+  NSArray<ENRMListMarkerDescriptor *> *_markers;
+}
+
+- (instancetype)initWithMarkers:(NSArray<ENRMListMarkerDescriptor *> *)markers
+{
+  if (self = [super init]) {
+    _markers = [markers copy];
+  }
+  return self;
+}
+
+- (NSUInteger)count
+{
+  return _markers.count;
+}
+
+- (id)objectAtIndex:(NSUInteger)index
+{
+  return _markers[index];
+}
+
+- (NSUInteger)hash
+{
+  return _markers.lastObject.hash;
+}
+
+@end
+
 @interface ListItemRenderer ()
 - (void)applyCheckedDecorationsTo:(NSMutableAttributedString *)output
                             range:(NSRange)range
@@ -184,7 +219,9 @@ - (void)renderNodeContent:(MarkdownASTNode *)node
   NSArray *existingMarkers = [output attribute:ListItemMarkerStartAttribute atIndex:anchorLocation effectiveRange:NULL];
   NSArray *markers =
       [existingMarkers isKindOfClass:[NSArray class]] ? [existingMarkers arrayByAddingObject:marker] : @[ marker ];
-  [output addAttribute:ListItemMarkerStartAttribute value:markers range:anchorRange];
+  [output addAttribute:ListItemMarkerStartAttribute
+                 value:[[ENRMListMarkerArray alloc] initWithMarkers:markers]
+                 range:anchorRange];
 
   if (isTask && isChecked) {
     [self applyCheckedDecorationsTo:output range:itemRange nestingLevel:nestingLevel];