// Copyright 2015 The Fuchsia 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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library fuchsia.ui.input;
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// TODO(jeffbrown): Redesign input event representation later.
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// The input dispatcher service allows the component which owns and controls
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// a view tree to dispatch input events to the views that it contains.
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//
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// This service can be retrieved from the |ViewTree| service provider.
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//
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// TODO(jeffbrown): Elaborate how input devices are registered with the
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// dispatcher so that applications can query their capabilities and distinguish
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// input coming from multiple sources concurrently.
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[Discoverable]
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interface InputDispatcher {
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// Dispatches an event through the view tree. The dispatcher will deliver
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// the event to the appropriate views based on the current state of the
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// tree, such as focus and the structure of the scene graph.
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//
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// The dispatcher expects the stream of events that it receives to be
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// internally consistent. For example, each pointer down must be matched
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// by a corresponding pointer up.
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//
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// It is an error to supply an inconsistent stream events to the dispatcher;
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// the connection will be closed.
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//
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// TODO(jeffbrown): Is this the right policy? It would certainly help
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// diagnose faults earlier.
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// TODO(jeffbrown): Decide whether there should be a way to track the
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// progress of input events. For testing purposes it is often desirable
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// to block the test until a sequence of events have been delivered and
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// handled. However these same mechanisms have proven to be brittle in
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// the past so it might be better to solve the problem some other way.
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1: DispatchEvent(InputEvent event);
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};
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