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Some render box subclasses have a specific layout contract that is tightly coupled with other render box subclasses (e.g. two private classes in a local project file). In these cases, it is also possible that they use a constraints object that is a subclass of `BoxConstraints`. To allow for this, this change makes the `constraints` argument to `RenderBox.computeDryLayout()` a covariant argument. For completeness' sake, this updates the other render objects in the rendering package to also use the covariant keyword for this argument.
107 lines
3.3 KiB
Dart
107 lines
3.3 KiB
Dart
// Copyright 2014 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/foundation.dart';
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import 'box.dart';
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import 'layer.dart';
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import 'object.dart';
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/// A rectangle upon which a backend texture is mapped.
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///
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/// Backend textures are images that can be applied (mapped) to an area of the
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/// Flutter view. They are created, managed, and updated using a
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/// platform-specific texture registry. This is typically done by a plugin
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/// that integrates with host platform video player, camera, or OpenGL APIs,
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/// or similar image sources.
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///
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/// A texture box refers to its backend texture using an integer ID. Texture
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/// IDs are obtained from the texture registry and are scoped to the Flutter
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/// view. Texture IDs may be reused after deregistration, at the discretion
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/// of the registry. The use of texture IDs currently unknown to the registry
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/// will silently result in a blank rectangle.
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///
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/// Texture boxes are repainted autonomously as dictated by the backend (e.g. on
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/// arrival of a video frame). Such repainting generally does not involve
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/// executing Dart code.
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///
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/// The size of the rectangle is determined by the parent, and the texture is
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/// automatically scaled to fit.
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///
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/// See also:
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///
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/// * [TextureRegistry](/javadoc/io/flutter/view/TextureRegistry.html)
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/// for how to create and manage backend textures on Android.
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/// * [TextureRegistry Protocol](/ios-embedder/protocol_flutter_texture_registry-p.html)
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/// for how to create and manage backend textures on iOS.
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class TextureBox extends RenderBox {
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/// Creates a box backed by the texture identified by [textureId], and use
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/// [filterQuality] to set texture's [FilterQuality].
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TextureBox({
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required int textureId,
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bool freeze = false,
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FilterQuality filterQuality = FilterQuality.low,
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}) : _textureId = textureId,
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_freeze = freeze,
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_filterQuality = filterQuality;
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/// The identity of the backend texture.
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int get textureId => _textureId;
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int _textureId;
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set textureId(int value) {
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if (value != _textureId) {
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_textureId = value;
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markNeedsPaint();
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}
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}
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/// When true the texture will not be updated with new frames.
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bool get freeze => _freeze;
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bool _freeze;
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set freeze(bool value) {
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if (value != _freeze) {
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_freeze = value;
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markNeedsPaint();
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}
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}
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/// {@macro flutter.widgets.Texture.filterQuality}
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FilterQuality get filterQuality => _filterQuality;
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FilterQuality _filterQuality;
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set filterQuality(FilterQuality value) {
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if (value != _filterQuality) {
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_filterQuality = value;
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markNeedsPaint();
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}
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}
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@override
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bool get sizedByParent => true;
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@override
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bool get alwaysNeedsCompositing => true;
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@override
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bool get isRepaintBoundary => true;
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@override
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@protected
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Size computeDryLayout(covariant BoxConstraints constraints) {
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return constraints.biggest;
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}
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@override
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bool hitTestSelf(Offset position) => true;
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@override
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void paint(PaintingContext context, Offset offset) {
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context.addLayer(TextureLayer(
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rect: Rect.fromLTWH(offset.dx, offset.dy, size.width, size.height),
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textureId: _textureId,
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freeze: freeze,
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filterQuality: _filterQuality,
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));
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}
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}
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