Perf: Performance optimization (#1964)

* Node.length, Node.offset caching added

* Unnecessary Document.from removed, method arguments changed accordingly

* root.toDelta check replaced with assertion

lib/src/models/documents/document.dart

@@ -354,10 +354,7 @@ class Document {
     } catch (e) {
       throw StateError('_delta compose failed');
     }
-
-    if (_delta != _root.toDelta()) {
-      throw StateError('Compose failed');
-    }
+    assert(_delta == _root.toDelta(), 'Compose failed');
     final change = DocChange(originalDelta, delta, changeSource);
     documentChangeObserver.add(change);
     history.handleDocChange(change);
@@ -442,7 +439,6 @@ class Document {
           doc.toString(), 'Document Delta cannot be empty.');
     }
 
-    // print(doc.last.data.runtimeType);
     assert((doc.last.data as String).endsWith('\n'));
 
     var offset = 0;

lib/src/models/documents/nodes/container.dart

@@ -47,25 +47,30 @@ abstract base class QuillContainer<T extends Node?> extends Node {
   /// Always returns fresh instance.
   T get defaultChild;
 
+  int? _length;
+
   /// Adds [node] to the end of this container children list.
   void add(T node) {
     assert(node?.parent == null);
     node?.parent = this;
     _children.add(node as Node);
+    clearLengthCache();
   }
 
   /// Adds [node] to the beginning of this container children list.
   void addFirst(T node) {
     assert(node?.parent == null);
     node?.parent = this;
     _children.addFirst(node as Node);
+    clearLengthCache();
   }
 
   /// Removes [node] from this container.
   void remove(T node) {
     assert(node?.parent == this);
     node?.parent = null;
     _children.remove(node as Node);
+    clearLengthCache();
   }
 
   /// Moves children of this node to [newParent].
@@ -118,11 +123,20 @@ abstract base class QuillContainer<T extends Node?> extends Node {
           .map((e) => e.toPlainText(embedBuilders, unknownEmbedBuilder))
           .join();
 
-  /// Content length of this node's children.
-  ///
-  /// To get number of children in this node use [childCount].
   @override
-  int get length => _children.fold(0, (cur, node) => cur + node.length);
+  int get length {
+    _length ??= _children.fold(0, (cur, node) => (cur ?? 0) + node.length);
+    return _length!;
+  }
+
+  @override
+  void clearLengthCache() {
+    _length = null;
+    clearOffsetCache();
+    if (parent != null) {
+      parent!.clearLengthCache();
+    }
+  }
 
   @override
   void insert(int index, Object data, Style? style) {

lib/src/models/documents/nodes/leaf.dart

@@ -24,18 +24,39 @@ abstract base class Leaf extends Node {
   /// Contents of this node, either a String if this is a [QuillText] or an
   /// [Embed] if this is an [BlockEmbed].
   Object get value => _value;
+
+  set value(Object v) {
+    _value = v;
+    _length = null;
+    clearOffsetCache();
+  }
+
   Object _value;
 
   @override
   Line? get parent => super.parent as Line?;
 
+  int? _length;
+
   @override
   int get length {
+    if (_length != null) {
+      return _length!;
+    }
     if (_value is String) {
-      return (_value as String).length;
+      _length = (_value as String).length;
+    } else {
+      // return 1 for embedded object
+      _length = 1;
+    }
+    return _length!;
+  }
+
+  @override
+  void clearLengthCache() {
+    if (parent != null) {
+      parent!.clearLengthCache();
     }
-    // return 1 for embedded object
-    return 1;
   }
 
   @override
@@ -47,6 +68,7 @@ abstract base class Leaf extends Node {
 
   @override
   void insert(int index, Object data, Style? style) {
+    final length = this.length;
     assert(index >= 0 && index <= length);
     final node = Leaf(data);
     if (index < length) {
@@ -75,6 +97,7 @@ abstract base class Leaf extends Node {
 
   @override
   void delete(int index, int? len) {
+    final length = this.length;
     assert(index < length);
 
     final local = math.min(length - index, len!);
@@ -117,15 +140,15 @@ abstract base class Leaf extends Node {
     // Merging it with previous node if style is the same.
     final prev = node.previous;
     if (!node.isFirst && prev is QuillText && prev.style == node.style) {
-      prev._value = prev.value + node.value;
+      prev.value = prev.value + node.value;
       node.unlink();
       node = prev;
     }
 
     // Merging it with next node if style is the same.
     final next = node.next;
     if (!node.isLast && next is QuillText && next.style == node.style) {
-      node._value = node.value + next.value;
+      node.value = node.value + next.value;
       next.unlink();
     }
   }
@@ -152,7 +175,7 @@ abstract base class Leaf extends Node {
 
     assert(this is QuillText);
     final text = _value as String;
-    _value = text.substring(0, index);
+    value = text.substring(0, index);
     final split = Leaf(text.substring(index))..applyStyle(style);
     insertAfter(split);
     return split;

lib/src/models/documents/nodes/line.dart

@@ -127,11 +127,11 @@ base class Line extends QuillContainer<Leaf?> {
     if (style == null) {
       return;
     }
-    final thisLength = length;
+    final length = this.length;
 
-    final local = math.min(thisLength - index, len!);
+    final local = math.min(length - index, len!);
     // If index is at newline character then this is a line/block style update.
-    final isLineFormat = (index + local == thisLength) && local == 1;
+    final isLineFormat = (index + local == length) && local == 1;
 
     if (isLineFormat) {
       assert(
@@ -145,7 +145,7 @@ base class Line extends QuillContainer<Leaf?> {
       assert(style.values.every((attr) =>
           attr.scope == AttributeScope.inline ||
           attr.scope == AttributeScope.ignore));
-      assert(index + local != thisLength);
+      assert(index + local != length);
       super.retain(index, local, style);
     }
 
@@ -158,6 +158,7 @@ base class Line extends QuillContainer<Leaf?> {
 
   @override
   void delete(int index, int? len) {
+    final length = this.length;
     final local = math.min(length - index, len!);
     final isLFDeleted = index + local == length; // Line feed
     if (isLFDeleted) {

lib/src/models/documents/nodes/node.dart

@@ -47,24 +47,41 @@ abstract base class Node extends LinkedListEntry<Node> {
   /// Length of this node in characters.
   int get length;
 
+  void clearLengthCache();
+
   Node clone() => newInstance()..applyStyle(style);
 
+  int? _offset;
+
   /// Offset in characters of this node relative to [parent] node.
   ///
   /// To get offset of this node in the document see [documentOffset].
   int get offset {
-    var offset = 0;
+    if (_offset != null) {
+      return _offset!;
+    }
 
     if (list == null || isFirst) {
-      return offset;
+      return 0;
+    }
+    var offset = 0;
+    for (final node in list!) {
+      if (node == this) {
+        break;
+      }
+      offset += node.length;
     }
 
-    var cur = this;
-    do {
-      cur = cur.previous!;
-      offset += cur.length;
-    } while (!cur.isFirst);
-    return offset;
+    _offset = offset;
+    return _offset!;
+  }
+
+  void clearOffsetCache() {
+    _offset = null;
+    final next = this.next;
+    if (next != null) {
+      next.clearOffsetCache();
+    }
   }
 
   /// Offset in characters of this node in the document.
@@ -100,18 +117,21 @@ abstract base class Node extends LinkedListEntry<Node> {
     assert(entry.parent == null && parent != null);
     entry.parent = parent;
     super.insertBefore(entry);
+    clearLengthCache();
   }
 
   @override
   void insertAfter(Node entry) {
     assert(entry.parent == null && parent != null);
     entry.parent = parent;
     super.insertAfter(entry);
+    clearLengthCache();
   }
 
   @override
   void unlink() {
     assert(parent != null);
+    clearLengthCache();
     parent = null;
     super.unlink();
   }

lib/src/models/rules/delete.dart

@@ -1,6 +1,7 @@
 import 'package:meta/meta.dart' show immutable;
 
 import '../../../quill_delta.dart';
+import '../../models/documents/document.dart';
 import '../documents/attribute.dart';
 import '../documents/nodes/embeddable.dart';
 import 'rule.dart';
@@ -26,9 +27,9 @@ class EnsureLastLineBreakDeleteRule extends DeleteRule {
   const EnsureLastLineBreakDeleteRule();
 
   @override
-  Delta? applyRule(Delta document, int index,
+  Delta? applyRule(Document document, int index,
       {int? len, Object? data, Attribute? attribute}) {
-    final itr = DeltaIterator(document)..skip(index + len!);
+    final itr = DeltaIterator(document.toDelta())..skip(index + len!);
 
     return Delta()
       ..retain(index)
@@ -43,9 +44,9 @@ class CatchAllDeleteRule extends DeleteRule {
   const CatchAllDeleteRule();
 
   @override
-  Delta applyRule(Delta document, int index,
+  Delta applyRule(Document document, int index,
       {int? len, Object? data, Attribute? attribute}) {
-    final itr = DeltaIterator(document)..skip(index + len!);
+    final itr = DeltaIterator(document.toDelta())..skip(index + len!);
 
     return Delta()
       ..retain(index)
@@ -64,9 +65,9 @@ class PreserveLineStyleOnMergeRule extends DeleteRule {
   const PreserveLineStyleOnMergeRule();
 
   @override
-  Delta? applyRule(Delta document, int index,
+  Delta? applyRule(Document document, int index,
       {int? len, Object? data, Attribute? attribute}) {
-    final itr = DeltaIterator(document)..skip(index);
+    final itr = DeltaIterator(document.toDelta())..skip(index);
     var op = itr.next(1);
     if (op.data != '\n') {
       return null;
@@ -121,9 +122,9 @@ class EnsureEmbedLineRule extends DeleteRule {
   const EnsureEmbedLineRule();
 
   @override
-  Delta? applyRule(Delta document, int index,
+  Delta? applyRule(Document document, int index,
       {int? len, Object? data, Attribute? attribute}) {
-    final itr = DeltaIterator(document);
+    final itr = DeltaIterator(document.toDelta());
 
     var op = itr.skip(index);
     final opAfter = itr.skip(index + 1);

lib/src/models/rules/format.dart

@@ -1,6 +1,7 @@
 import 'package:meta/meta.dart' show immutable;
 
 import '../../../quill_delta.dart';
+import '../../models/documents/document.dart';
 import '../documents/attribute.dart';
 import 'rule.dart';
 
@@ -28,7 +29,7 @@ class ResolveLineFormatRule extends FormatRule {
 
   @override
   Delta? applyRule(
-    Delta document,
+    Document document,
     int index, {
     int? len,
     Object? data,
@@ -41,7 +42,7 @@ class ResolveLineFormatRule extends FormatRule {
     // Apply line styles to all newline characters within range of this
     // retain operation.
     var result = Delta()..retain(index);
-    final itr = DeltaIterator(document)..skip(index);
+    final itr = DeltaIterator(document.toDelta())..skip(index);
     Operation op;
     for (var cur = 0; cur < len! && itr.hasNext; cur += op.length!) {
       op = itr.next(len - cur);
@@ -119,7 +120,7 @@ class FormatLinkAtCaretPositionRule extends FormatRule {
 
   @override
   Delta? applyRule(
-    Delta document,
+    Document document,
     int index, {
     int? len,
     Object? data,
@@ -130,7 +131,7 @@ class FormatLinkAtCaretPositionRule extends FormatRule {
     }
 
     final delta = Delta();
-    final itr = DeltaIterator(document);
+    final itr = DeltaIterator(document.toDelta());
     final before = itr.skip(index), after = itr.next();
     int? beg = index, retain = 0;
     if (before != null && before.hasAttribute(attribute.key)) {
@@ -159,7 +160,7 @@ class ResolveInlineFormatRule extends FormatRule {
 
   @override
   Delta? applyRule(
-    Delta document,
+    Document document,
     int index, {
     int? len,
     Object? data,
@@ -170,7 +171,7 @@ class ResolveInlineFormatRule extends FormatRule {
     }
 
     final delta = Delta()..retain(index);
-    final itr = DeltaIterator(document)..skip(index);
+    final itr = DeltaIterator(document.toDelta())..skip(index);
 
     Operation op;
     for (var cur = 0; cur < len! && itr.hasNext; cur += op.length!) {
@@ -205,7 +206,7 @@ class ResolveImageFormatRule extends FormatRule {
 
   @override
   Delta? applyRule(
-    Delta document,
+    Document document,
     int index, {
     int? len,
     Object? data,