Fix spurious ANRs in native activities.

Some native activities experienced ANRs when the input consumer
deferred an input event due to client-side batching.  If the
input channel was fully emptied then the client had no way of
knowing that it should wake up to handle the deferred input event.

This patch also fixes some lock issues in the native activity
input queue implementation.  In at least one error case, it
was possible for a function to exit without releasing the lock.

Bug: 6051176
Change-Id: I4d9d843237e69b9834f8d8b360031b677fcab8c3

2 files changed, 43 insertions, 1 deletions

diff --git a/include/androidfw/Input.h b/include/androidfw/Input.h
index f5db6e2..a4ebd95 100644
--- a/include/androidfw/Input.h
+++ b/include/androidfw/Input.h
@@ -616,6 +616,26 @@ private:
 };
 
 /*
+ * An input event factory implementation that maintains a pool of input events.
+ */
+class PooledInputEventFactory : public InputEventFactoryInterface {
+public:
+    PooledInputEventFactory(size_t maxPoolSize = 20);
+    virtual ~PooledInputEventFactory();
+
+    virtual KeyEvent* createKeyEvent();
+    virtual MotionEvent* createMotionEvent();
+
+    void recycle(InputEvent* event);
+
+private:
+    const size_t mMaxPoolSize;
+
+    Vector<KeyEvent*> mKeyEventPool;
+    Vector<MotionEvent*> mMotionEventPool;
+};
+
+/*
  * Calculates the velocity of pointer movements over time.
  */
 class VelocityTracker {
diff --git a/include/androidfw/InputTransport.h b/include/androidfw/InputTransport.h
index a846e65..29c296e 100644
--- a/include/androidfw/InputTransport.h
+++ b/include/androidfw/InputTransport.h
@@ -292,7 +292,29 @@ public:
      */
     status_t sendFinishedSignal(uint32_t seq, bool handled);
 
-    /* Returns true if there is a pending batch. */
+    /* Returns true if there is a deferred event waiting.
+     *
+     * Should be called after calling consume() to determine whether the consumer
+     * has a deferred event to be processed.  Deferred events are somewhat special in
+     * that they have already been removed from the input channel.  If the input channel
+     * becomes empty, the client may need to do extra work to ensure that it processes
+     * the deferred event despite the fact that the inptu channel's file descriptor
+     * is not readable.
+     *
+     * One option is simply to call consume() in a loop until it returns WOULD_BLOCK.
+     * This guarantees that all deferred events will be processed.
+     *
+     * Alternately, the caller can call hasDeferredEvent() to determine whether there is
+     * a deferred event waiting and then ensure that its event loop wakes up at least
+     * one more time to consume the deferred event.
+     */
+    bool hasDeferredEvent() const;
+
+    /* Returns true if there is a pending batch.
+     *
+     * Should be called after calling consume() with consumeBatches == false to determine
+     * whether consume() should be called again later on with consumeBatches == true.
+     */
     bool hasPendingBatch() const;
 
 private: