commit 8dc55396fc9bc425b5e2c82e76a38080f2a655ff
author Dan Stoza <stoza@google.com> Tue Nov 04 11:37:46 2014 -0800
committer Dan Stoza <stoza@google.com> Fri Nov 07 10:39:13 2014 -0800
tree 36dfc0172e525db15531c9074a81096862287edf
parent 793fc0e13d25bdecda1219999f8be2cb3c121d20

Add a BufferItem parameter to onFrameAvailable

Passes the BufferItem for the queued buffer to the onFrameAvailable
callback so the consumer can track the BufferQueue's contents. Also
adds an onFrameReplaced callback, which is necessary if the consumer
wants to do anything more than simple queue length tracking.

Bug: 18111837
Change-Id: If9d07229c9b586c668e5f99074e9b63b0468feb0

libs/gui/BufferQueueProducer.cpp

diff --git a/libs/gui/BufferQueueProducer.cpp b/libs/gui/BufferQueueProducer.cpp
index 284ddb2..4d3b008 100644
--- a/libs/gui/BufferQueueProducer.cpp
+++ b/libs/gui/BufferQueueProducer.cpp
@@ -39,7 +39,11 @@
     mSlots(core->mSlots),
     mConsumerName(),
     mStickyTransform(0),
-    mLastQueueBufferFence(Fence::NO_FENCE) {}
+    mLastQueueBufferFence(Fence::NO_FENCE),
+    mCallbackMutex(),
+    mNextCallbackTicket(0),
+    mCurrentCallbackTicket(0),
+    mCallbackCondition() {}
 
 BufferQueueProducer::~BufferQueueProducer() {}
 
@@ -542,7 +546,10 @@
             return BAD_VALUE;
     }
 
-    sp<IConsumerListener> listener;
+    sp<IConsumerListener> frameAvailableListener;
+    sp<IConsumerListener> frameReplacedListener;
+    int callbackTicket = 0;
+    BufferItem item;
     { // Autolock scope
         Mutex::Autolock lock(mCore->mMutex);
 
@@ -598,7 +605,6 @@
         ++mCore->mFrameCounter;
         mSlots[slot].mFrameNumber = mCore->mFrameCounter;
 
-        BufferItem item;
         item.mAcquireCalled = mSlots[slot].mAcquireCalled;
         item.mGraphicBuffer = mSlots[slot].mGraphicBuffer;
         item.mCrop = crop;
@@ -619,7 +625,7 @@
             // When the queue is empty, we can ignore mDequeueBufferCannotBlock
             // and simply queue this buffer
             mCore->mQueue.push_back(item);
-            listener = mCore->mConsumerListener;
+            frameAvailableListener = mCore->mConsumerListener;
         } else {
             // When the queue is not empty, we need to look at the front buffer
             // state to see if we need to replace it
@@ -635,9 +641,10 @@
                 }
                 // Overwrite the droppable buffer with the incoming one
                 *front = item;
+                frameReplacedListener = mCore->mConsumerListener;
             } else {
                 mCore->mQueue.push_back(item);
-                listener = mCore->mConsumerListener;
+                frameAvailableListener = mCore->mConsumerListener;
             }
         }
 
@@ -648,6 +655,9 @@
                 mCore->mTransformHint, mCore->mQueue.size());
 
         ATRACE_INT(mCore->mConsumerName.string(), mCore->mQueue.size());
+
+        // Take a ticket for the callback functions
+        callbackTicket = mNextCallbackTicket++;
     } // Autolock scope
 
     // Wait without lock held
@@ -659,9 +669,27 @@
         mLastQueueBufferFence = fence;
     }
 
-    // Call back without lock held
-    if (listener != NULL) {
-        listener->onFrameAvailable();
+    // Don't send the GraphicBuffer through the callback, and don't send
+    // the slot number, since the consumer shouldn't need it
+    item.mGraphicBuffer.clear();
+    item.mSlot = BufferItem::INVALID_BUFFER_SLOT;
+
+    // Call back without the main BufferQueue lock held, but with the callback
+    // lock held so we can ensure that callbacks occur in order
+    {
+        Mutex::Autolock lock(mCallbackMutex);
+        while (callbackTicket != mCurrentCallbackTicket) {
+            mCallbackCondition.wait(mCallbackMutex);
+        }
+
+        if (frameAvailableListener != NULL) {
+            frameAvailableListener->onFrameAvailable(item);
+        } else if (frameReplacedListener != NULL) {
+            frameReplacedListener->onFrameReplaced(item);
+        }
+
+        ++mCurrentCallbackTicket;
+        mCallbackCondition.broadcast();
     }
 
     return NO_ERROR;