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177a6128c1
_This PR is part of the multiview engine project. For a complete roadmap, see [this doc](https://docs.google.com/document/d/10APhzRDR7XqjWdbYWpFfKur7DPiz_HvSKNcLvcyA9vg/edit?resourcekey=0-DfGcg4-XWRMMZF__C1nmcA)._ ------ This PR adds view management to all engine classes that need it. View management here basically means `AddView` and `RemoveView` methods, and most importantly, how to handle the implicit view. The implicit view is a special view that's handled differently than all the other "regular views", since it keeps the behavior of the current single view of Flutter. Detailed introduction can be found in `Settings.implicit_view_enabled`. The following two graphs show the difference between initializing with/without the implicit view and creating regular views. <img width="879" alt="image" src="https://github.com/flutter/engine/assets/1596656/31244685-d9d3-4c9a-9a9e-6e8540a5711e"> <img width="864" alt="image" src="https://github.com/flutter/engine/assets/1596656/e2dd4b8c-57e3-428d-8547-834fb270052b"> <img width="860" alt="image" src="https://github.com/flutter/engine/assets/1596656/58dae687-8c17-434e-ae24-a48c2d8fa5fa"> [C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
39 lines
1.8 KiB
C++
39 lines
1.8 KiB
C++
// Copyright 2013 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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#ifndef FLUTTER_COMMON_CONSTANTS_H_
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#define FLUTTER_COMMON_CONSTANTS_H_
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namespace flutter {
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constexpr double kMegaByteSizeInBytes = (1 << 20);
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// The ID for the implicit view if the implicit view is enabled.
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//
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// The implicit view is a compatibility mechanism to help the transition from
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// the older single-view APIs to the newer multi-view APIs. The two sets of APIs
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// use different models for view management. The implicit view mechanism allows
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// single-view APIs to operate a special view as if other views don't exist.
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//
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// In the regular multi-view model, all views should be created by
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// `Shell::AddView` before being used, and removed by `Shell::RemoveView` to
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// signify that they are gone. If a view is added or removed, the framework
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// (`PlatformDispatcher`) will be notified. New view IDs are always unique,
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// never reused. Operating a non-existing view is an error.
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//
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// The implicit view is another special view in addition to the "regular views"
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// as above. The shell starts up having the implicit view, which has a fixed
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// view ID of `kFlutterImplicitViewId` and is available throughout the lifetime
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// of the shell. `Shell::AddView` or `RemoveView` must not be called for this
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// view. Even when the window that shows the view is closed, the framework is
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// unaware and might continue rendering into or operating this view.
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//
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// The single-view APIs, which are APIs that do not specify view IDs, operate
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// the implicit view. The multi-view APIs can operate all views, including the
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// implicit view if the target ID is `kFlutterImplicitViewId`, unless specified
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// otherwise.
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constexpr int64_t kFlutterImplicitViewId = 0;
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} // namespace flutter
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#endif // FLUTTER_COMMON_CONSTANTS_H_
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