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Commit 17761fff authored by Michael Wright's avatar Michael Wright
Browse files

Isolate batched input scheduling logic. 

Having whether something is currently scheduled get modified in the
actual processing logic and away from the scheduling logic makes it
unnecessarily more difficult to reason about.

In this case, we were only checking whether the Choreographer-aligned
runnable was actually scheduled before we'd consume input. When trying
to unbuffer dispatches so that things were no longer
Choreographer-aligned, however, we'd unschedule the that runnable just
before we tried to consume input and hence just before the check . This
meant we never actually consumed the batches until the next one came in
where we would then consume them immediately.  Worse, if another one
never came in then we'd never actually consume the batch.

By removing the scheduling logic from the processing logic we avoid this
situation. Now only the schedule, unschedule, and actual runnable logic
touch their own scheduled state, so that we don't have to consider the
two pieces of logic together except in isolated places.

Bug: 158540186
Bug: 159239700

Test: manual, using app that injects unbuffered dispatch requests either
      at ACTION_DOWN or first ACTION_MOVE
Change-Id: I7521a5a16ed52afc41261f501128b5498ea0602c
parent 16868fbe

core/java/android/view/ViewRootImpl.java

+20 −17
Original line number Diff line number Diff line
@@ -8107,7 +8107,9 @@ public final class ViewRootImpl implements ViewParent, 
    }



    void scheduleConsumeBatchedInput() {

        if (!mConsumeBatchedInputScheduled) {

        // If anything is currently scheduled to consume batched input then there's no point in

        // scheduling it again.

        if (!mConsumeBatchedInputScheduled && !mConsumeBatchedInputImmediatelyScheduled) {

            mConsumeBatchedInputScheduled = true;

            mChoreographer.postCallback(Choreographer.CALLBACK_INPUT,

                    mConsumedBatchedInputRunnable, null);
@@ -8130,22 +8132,15 @@ public final class ViewRootImpl implements ViewParent, 
        }

    }



    void doConsumeBatchedInput(long frameTimeNanos) {

        if (mConsumeBatchedInputScheduled) {

            mConsumeBatchedInputScheduled = false;

    boolean doConsumeBatchedInput(long frameTimeNanos) {

        final boolean consumedBatches;

        if (mInputEventReceiver != null) {

                if (mInputEventReceiver.consumeBatchedInputEvents(frameTimeNanos)

                        && frameTimeNanos != -1) {

                    // If we consumed a batch here, we want to go ahead and schedule the

                    // consumption of batched input events on the next frame. Otherwise, we would

                    // wait until we have more input events pending and might get starved by other

                    // things occurring in the process. If the frame time is -1, however, then

                    // we're in a non-batching mode, so there's no need to schedule this.

                    scheduleConsumeBatchedInput();

                }

            consumedBatches = mInputEventReceiver.consumeBatchedInputEvents(frameTimeNanos);

        } else {

            consumedBatches = false;

        }

        doProcessInputEvents();

        }

        return consumedBatches;

    }



    final class TraversalRunnable implements Runnable {
@@ -8218,7 +8213,14 @@ public final class ViewRootImpl implements ViewParent, 
    final class ConsumeBatchedInputRunnable implements Runnable {

        @Override

        public void run() {

            doConsumeBatchedInput(mChoreographer.getFrameTimeNanos());

            mConsumeBatchedInputScheduled = false;

            if (doConsumeBatchedInput(mChoreographer.getFrameTimeNanos())) {

                // If we consumed a batch here, we want to go ahead and schedule the

                // consumption of batched input events on the next frame. Otherwise, we would

                // wait until we have more input events pending and might get starved by other

                // things occurring in the process.

                scheduleConsumeBatchedInput();

            }

        }

    }

    final ConsumeBatchedInputRunnable mConsumedBatchedInputRunnable =
@@ -8228,6 +8230,7 @@ public final class ViewRootImpl implements ViewParent, 
    final class ConsumeBatchedInputImmediatelyRunnable implements Runnable {

        @Override

        public void run() {

            mConsumeBatchedInputImmediatelyScheduled = false;

            doConsumeBatchedInput(-1);

        }

    }