refa: danmaku & feat: scroll fixed velocity (#1791)

lib/utils/extension/box_ext.dart

@@ -0,0 +1,28 @@
+import 'package:collection/collection.dart';
+import 'package:hive/hive.dart';
+
+extension BoxExt<E> on Box<E> {
+  bool equal(dynamic key, E value) {
+    return const DeepCollectionEquality().equals(value, get(key));
+  }
+
+  Future<void>? putNE(dynamic key, E value) {
+    if (!equal(key, value)) {
+      return put(key, value);
+    }
+    return null;
+  }
+
+  Future<void>? putAllNE(Map<dynamic, E> entries) {
+    final Map<dynamic, E> newEntries = {};
+    entries.forEach((key, value) {
+      if (!equal(key, value)) {
+        newEntries[key] = value;
+      }
+    });
+    if (newEntries.isNotEmpty) {
+      return putAll(newEntries);
+    }
+    return null;
+  }
+}

lib/utils/extension/num_ext.dart

@@ -18,7 +18,7 @@ extension IntExt on int? {
 
 extension DoubleExt on double {
   double toPrecision(int fractionDigits) {
-    final mod = pow(10, fractionDigits.toDouble()).toDouble();
-    return ((this * mod).round().toDouble() / mod);
+    final mod = pow(10, fractionDigits).toDouble();
+    return (this * mod).roundToDouble() / mod;
   }
 }