yubioath-flutter/lib/widgets/utf8_utils.dart
2022-11-22 10:24:11 +01:00

54 lines
2.0 KiB
Dart
Executable File

/*
* Copyright (C) 2022 Yubico.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
/// Get the number of bytes used by a String when encoded to UTF-8.
int byteLength(String value) => utf8.encode(value).length;
/// Builds a counter widget showing number of bytes used/available.
///
/// Set this as a [TextField.buildCounter] callback to show the number of bytes
/// used rather than number of characters. [currentValue] should always match
/// the input text value to measure.
InputCounterWidgetBuilder buildByteCounterFor(String currentValue) =>
(context, {required currentLength, required isFocused, maxLength}) {
final theme = Theme.of(context);
final caption = theme.textTheme.caption;
final style = (byteLength(currentValue) <= (maxLength ?? 0))
? caption
: caption?.copyWith(color: theme.errorColor);
return Text(
maxLength != null ? '${byteLength(currentValue)}/$maxLength' : '',
style: style,
semanticsLabel: 'Character count',
);
};
/// Limits the input in length based on the byte length when encoded.
/// This is generally used together with [buildByteCounterFor].
TextInputFormatter limitBytesLength(int maxByteLength) =>
TextInputFormatter.withFunction((oldValue, newValue) {
final newLength = byteLength(newValue.text);
if (newLength <= maxByteLength) {
return newValue;
}
return oldValue;
});