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/*
* Copyright (C) 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.view;
import static android.os.IInputConstants.INVALID_INPUT_EVENT_ID;
import static android.view.InputDevice.SOURCE_TOUCHSCREEN;
/**
* Process input events and assign input event id to a specific frame.
*
* The assigned input event id is determined by where the current gesture is relative to the vsync.
* In the middle of the gesture (we already processed some input events, and already received at
* least 1 vsync), the latest InputEvent is assigned to the next frame.
* If a gesture just started, then the ACTION_DOWN event will be assigned to the next frame.
*
* Consider the following sequence:
* DOWN -> VSYNC 1 -> MOVE 1 -> MOVE 2 -> VSYNC 2.
*
* For VSYNC 1, we will assign the "DOWN" input event.
* For VSYNC 2, we will assign the "MOVE 2" input event.
*
* Consider another sequence:
* DOWN -> MOVE 1 -> MOVE 2 -> VSYNC 1 -> MOVE 3 -> VSYNC 2.
*
* For VSYNC 1, we will still assign the "DOWN" input event. That means that "MOVE 1" and "MOVE 2"
* events are not attributed to any frame.
* For VSYNC 2, the "MOVE 3" input event will be assigned.
*
* @hide
*/
public class InputEventAssigner {
private static final String TAG = "InputEventAssigner";
private boolean mHasUnprocessedDown = false;
private int mDownEventId = INVALID_INPUT_EVENT_ID;
/**
* Notify InputEventAssigner that a frame has been processed. We no longer need to keep track of
* the DOWN event because a frame has already been produced for it.
*/
public void notifyFrameProcessed() {
// Mark completion of this frame. Use newest input event from now on.
mHasUnprocessedDown = false;
}
/**
* Process the provided input event to determine which event id to assign to the current frame.
* @param event the input event currently being processed
* @return the id of the input event to use for the current frame
*/
public int processEvent(InputEvent event) {
if (event instanceof MotionEvent) {
MotionEvent motionEvent = (MotionEvent) event;
if (motionEvent.isFromSource(SOURCE_TOUCHSCREEN)) {
final int action = motionEvent.getActionMasked();
if (action == MotionEvent.ACTION_DOWN) {
mHasUnprocessedDown = true;
mDownEventId = event.getId();
}
if (mHasUnprocessedDown && action == MotionEvent.ACTION_MOVE) {
return mDownEventId;
}
if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
mHasUnprocessedDown = false;
}
}
}
return event.getId();
}
}
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