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70 lines
2.4 KiB
Dart
70 lines
2.4 KiB
Dart
// Copyright 2018 The Chromium 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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part of dart.ui;
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/// An wrapper for a raw callback handle.
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class CallbackHandle {
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final int _handle;
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/// Create an instance using a raw callback handle.
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///
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/// Only values produced by a call to [CallbackHandle.toRawHandle] should be
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/// used, otherwise this object will be an invalid handle.
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CallbackHandle.fromRawHandle(this._handle)
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: assert(_handle != null, "'_handle' must not be null.");
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/// Get the raw callback handle to pass over a [MethodChannel] or isolate
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/// port.
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int toRawHandle() => _handle;
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@override
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int get hashCode => _handle;
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@override
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bool operator ==(dynamic other) =>
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(other is CallbackHandle) && (_handle == other._handle);
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}
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/// Functionality for Flutter plugin authors.
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abstract class PluginUtilities {
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// This class is only a namespace, and should not be instantiated or
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// extended directly.
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factory PluginUtilities._() => null;
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static Map<Function, CallbackHandle> _forwardCache =
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<Function, CallbackHandle>{};
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static Map<CallbackHandle, Function> _backwardCache =
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<CallbackHandle, Function>{};
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/// Get a handle to a named top-level or static callback function which can
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/// be easily passed between isolates.
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///
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/// `callback` must not be null.
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///
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/// Returns a [CallbackHandle] that can be provided to
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/// [PluginUtilities.getCallbackFromHandle] to retrieve a tear-off of the
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/// original callback. If `callback` is not a top-level or static function,
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/// null is returned.
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static CallbackHandle getCallbackHandle(Function callback) {
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assert(callback != null, "'callback' must not be null.");
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return _forwardCache.putIfAbsent(callback,
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() => new CallbackHandle.fromRawHandle(_getCallbackHandle(callback)));
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}
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/// Get a tear-off of a named top-level or static callback represented by a
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/// handle.
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///
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/// `handle` must not be null.
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///
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/// If `handle` is not a valid handle returned by
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/// [PluginUtilities.getCallbackHandle], null is returned. Otherwise, a
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/// tear-off of the callback associated with `handle` is returned.
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static Function getCallbackFromHandle(CallbackHandle handle) {
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assert(handle != null, "'handle' must not be null.");
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return _backwardCache.putIfAbsent(
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handle, () => _getCallbackFromHandle(handle.toRawHandle()));
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}
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}
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