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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.
/// Flutter code sample for [SelectableRegion].
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
void main() => runApp(const MyApp());
class MyApp extends StatelessWidget {
const MyApp({super.key});
static const String _title = 'Flutter Code Sample';
@override
Widget build(BuildContext context) {
return MaterialApp(
title: _title,
home: SelectionArea(
child: Scaffold(
appBar: AppBar(title: const Text(_title)),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: const <Widget>[
Text('Select this icon', style: TextStyle(fontSize: 30)),
SizedBox(height: 10),
MySelectableAdapter(child: Icon(Icons.key, size: 30)),
],
),
),
),
),
);
}
}
class MySelectableAdapter extends StatelessWidget {
const MySelectableAdapter({super.key, required this.child});
final Widget child;
@override
Widget build(BuildContext context) {
final SelectionRegistrar? registrar = SelectionContainer.maybeOf(context);
if (registrar == null) {
return child;
}
return MouseRegion(
cursor: SystemMouseCursors.text,
child: _SelectableAdapter(
registrar: registrar,
child: child,
),
);
}
}
class _SelectableAdapter extends SingleChildRenderObjectWidget {
const _SelectableAdapter({
required this.registrar,
required Widget child,
}) : super(child: child);
final SelectionRegistrar registrar;
@override
_RenderSelectableAdapter createRenderObject(BuildContext context) {
return _RenderSelectableAdapter(
DefaultSelectionStyle.of(context).selectionColor!,
registrar,
);
}
@override
void updateRenderObject(BuildContext context, _RenderSelectableAdapter renderObject) {
renderObject
..selectionColor = DefaultSelectionStyle.of(context).selectionColor!
..registrar = registrar;
}
}
class _RenderSelectableAdapter extends RenderProxyBox with Selectable, SelectionRegistrant {
_RenderSelectableAdapter(
Color selectionColor,
SelectionRegistrar registrar,
) : _selectionColor = selectionColor,
_geometry = ValueNotifier<SelectionGeometry>(_noSelection) {
this.registrar = registrar;
_geometry.addListener(markNeedsPaint);
}
static const SelectionGeometry _noSelection = SelectionGeometry(status: SelectionStatus.none, hasContent: true);
final ValueNotifier<SelectionGeometry> _geometry;
Color get selectionColor => _selectionColor;
late Color _selectionColor;
set selectionColor(Color value) {
if (_selectionColor == value) {
return;
}
_selectionColor = value;
markNeedsPaint();
}
// ValueListenable APIs
@override
void addListener(VoidCallback listener) => _geometry.addListener(listener);
@override
void removeListener(VoidCallback listener) => _geometry.removeListener(listener);
@override
SelectionGeometry get value => _geometry.value;
// Selectable APIs.
// Adjust this value to enlarge or shrink the selection highlight.
static const double _padding = 10.0;
Rect _getSelectionHighlightRect() {
return Rect.fromLTWH(
0 - _padding,
0 - _padding,
size.width + _padding * 2,
size.height + _padding * 2
);
}
Offset? _start;
Offset? _end;
void _updateGeometry() {
if (_start == null || _end == null) {
_geometry.value = _noSelection;
return;
}
final Rect renderObjectRect = Rect.fromLTWH(0, 0, size.width, size.height);
final Rect selectionRect = Rect.fromPoints(_start!, _end!);
if (renderObjectRect.intersect(selectionRect).isEmpty) {
_geometry.value = _noSelection;
} else {
final Rect selectionRect = _getSelectionHighlightRect();
final SelectionPoint firstSelectionPoint = SelectionPoint(
localPosition: selectionRect.bottomLeft,
lineHeight: selectionRect.size.height,
handleType: TextSelectionHandleType.left,
);
final SelectionPoint secondSelectionPoint = SelectionPoint(
localPosition: selectionRect.bottomRight,
lineHeight: selectionRect.size.height,
handleType: TextSelectionHandleType.right,
);
final bool isReversed;
if (_start!.dy > _end!.dy) {
isReversed = true;
} else if (_start!.dy < _end!.dy) {
isReversed = false;
} else {
isReversed = _start!.dx > _end!.dx;
}
_geometry.value = SelectionGeometry(
status: SelectionStatus.uncollapsed,
hasContent: true,
startSelectionPoint: isReversed ? secondSelectionPoint : firstSelectionPoint,
endSelectionPoint: isReversed ? firstSelectionPoint : secondSelectionPoint,
);
}
}
@override
SelectionResult dispatchSelectionEvent(SelectionEvent event) {
SelectionResult result = SelectionResult.none;
switch (event.type) {
case SelectionEventType.startEdgeUpdate:
case SelectionEventType.endEdgeUpdate:
final Rect renderObjectRect = Rect.fromLTWH(0, 0, size.width, size.height);
// Normalize offset in case it is out side of the rect.
final Offset point = globalToLocal((event as SelectionEdgeUpdateEvent).globalPosition);
final Offset adjustedPoint = SelectionUtils.adjustDragOffset(renderObjectRect, point);
if (event.type == SelectionEventType.startEdgeUpdate) {
_start = adjustedPoint;
} else {
_end = adjustedPoint;
}
result = SelectionUtils.getResultBasedOnRect(renderObjectRect, point);
break;
case SelectionEventType.clear:
_start = _end = null;
break;
case SelectionEventType.selectAll:
case SelectionEventType.selectWord:
_start = Offset.zero;
_end = Offset.infinite;
break;
}
_updateGeometry();
return result;
}
// This method is called when users want to copy selected content in this
// widget into clipboard.
@override
SelectedContent? getSelectedContent() {
return value.hasSelection ? const SelectedContent(plainText: 'Custom Text') : null;
}
LayerLink? _startHandle;
LayerLink? _endHandle;
@override
void pushHandleLayers(LayerLink? startHandle, LayerLink? endHandle) {
if (_startHandle == startHandle && _endHandle == endHandle) {
return;
}
_startHandle = startHandle;
_endHandle = endHandle;
markNeedsPaint();
}
@override
void paint(PaintingContext context, Offset offset) {
super.paint(context, offset);
if (!_geometry.value.hasSelection) {
return;
}
// Draw the selection highlight.
final Paint selectionPaint = Paint()
..style = PaintingStyle.fill
..color = _selectionColor;
context.canvas.drawRect(_getSelectionHighlightRect().shift(offset), selectionPaint);
// Push the layer links if any.
if (_startHandle != null) {
context.pushLayer(
LeaderLayer(
link: _startHandle!,
offset: offset + value.startSelectionPoint!.localPosition,
),
(PaintingContext context, Offset offset) { },
Offset.zero,
);
}
if (_endHandle != null) {
context.pushLayer(
LeaderLayer(
link: _endHandle!,
offset: offset + value.endSelectionPoint!.localPosition,
),
(PaintingContext context, Offset offset) { },
Offset.zero,
);
}
}
@override
void dispose() {
_geometry.dispose();
super.dispose();
}
}