55 lines
1.5 KiB
Dart
55 lines
1.5 KiB
Dart
import 'package:flutter/services.dart';
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extension on String {
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int getBeginningOfPreviousLine(int startingIndex) {
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for (var i = startingIndex; i >= 0; i--) {
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if (this[i] == '\n') return i + 1;
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}
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return 0;
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}
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// returns the line that ends at endingIndex
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String lineBefore(int endingIndex) {
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return substring(getBeginningOfPreviousLine(endingIndex), endingIndex + 1);
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}
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}
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extension on TextEditingValue {
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/// Append a string after the cursor
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TextEditingValue append(String s) {
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final beg = text.substring(0, selection.baseOffset);
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final end = text.substring(selection.baseOffset);
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return copyWith(
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text: '$beg$s$end',
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selection: selection.copyWith(
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baseOffset: selection.baseOffset + s.length,
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extentOffset: selection.extentOffset + s.length,
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),
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);
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}
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}
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/// Provides convinience formatting in markdown text fields
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class MarkdownFormatter extends TextInputFormatter {
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@override
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TextEditingValue formatEditUpdate(
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TextEditingValue oldValue, TextEditingValue newValue) {
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if (oldValue.text.length > newValue.text.length) return newValue;
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final char = newValue.text[newValue.selection.baseOffset - 1];
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if (char == '\n') {
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final lineBefore =
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newValue.text.lineBefore(newValue.selection.baseOffset - 2);
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if (lineBefore.startsWith('- ')) {
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return newValue.append('- ');
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}
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if (lineBefore.startsWith('* ')) {
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return newValue.append('* ');
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}
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}
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return newValue;
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}
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}
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