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// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'package:engine/ui.dart' show TextRange;
import 'text_editing.dart';
export 'package:engine/ui.dart' show TextPosition, TextRange;
export 'text_editing.dart' show TextSelection;
/// A read-only interface for accessing visual information about the
/// implementing text.
abstract class TextLayoutMetrics {
// TODO(gspencergoog): replace when we expose this ICU information.
/// Check if the given code unit is a white space or separator
/// character.
///
/// Includes newline characters from ASCII and separators from the
/// [unicode separator category](https://www.compart.com/en/unicode/category/Zs)
static bool isWhitespace(int codeUnit) {
switch (codeUnit) {
case 0x9: // horizontal tab
case 0xA: // line feed
case 0xB: // vertical tab
case 0xC: // form feed
case 0xD: // carriage return
case 0x1C: // file separator
case 0x1D: // group separator
case 0x1E: // record separator
case 0x1F: // unit separator
case 0x20: // space
case 0xA0: // no-break space
case 0x1680: // ogham space mark
case 0x2000: // en quad
case 0x2001: // em quad
case 0x2002: // en space
case 0x2003: // em space
case 0x2004: // three-per-em space
case 0x2005: // four-er-em space
case 0x2006: // six-per-em space
case 0x2007: // figure space
case 0x2008: // punctuation space
case 0x2009: // thin space
case 0x200A: // hair space
case 0x202F: // narrow no-break space
case 0x205F: // medium mathematical space
case 0x3000: // ideographic space
break;
default:
return false;
}
return true;
}
/// Check if the given code unit is a line terminator character.
///
/// Includes newline characters from ASCII
/// (https://www.unicode.org/standard/reports/tr13/tr13-5.html).
static bool isLineTerminator(int codeUnit) {
switch (codeUnit) {
case 0x0A: // line feed
case 0x0B: // vertical feed
case 0x0C: // form feed
case 0x0D: // carriage return
case 0x85: // new line
case 0x2028: // line separator
case 0x2029: // paragraph separator
return true;
default:
return false;
}
}
/// {@template flutter.services.TextLayoutMetrics.getLineAtOffset}
/// Return a [TextSelection] containing the line of the given [TextPosition].
/// {@endtemplate}
TextSelection getLineAtOffset(TextPosition position);
/// {@macro flutter.painting.TextPainter.getWordBoundary}
TextRange getWordBoundary(TextPosition position);
/// {@template flutter.services.TextLayoutMetrics.getTextPositionAbove}
/// Returns the TextPosition above the given offset into the text.
///
/// If the offset is already on the first line, the given offset will be
/// returned.
/// {@endtemplate}
TextPosition getTextPositionAbove(TextPosition position);
/// {@template flutter.services.TextLayoutMetrics.getTextPositionBelow}
/// Returns the TextPosition below the given offset into the text.
///
/// If the offset is already on the last line, the given offset will be
/// returned.
/// {@endtemplate}
TextPosition getTextPositionBelow(TextPosition position);
}