commit 670b3f73e9f97dc6031e71405e7dcb4da118ba37
author Vishnu Nair <vishnun@google.com> Tue Sep 29 17:52:18 2020 -0700
committer Vishnu Nair <vishnun@google.com> Wed Sep 30 15:14:43 2020 -0700
tree 0f1991f4c7de2fa976d8edc14a2ba523d0556c1f
parent 6b7c5c9425496be2166fccf2ab14e061b5a20fa3

Add buffer rejection logic to BlastBufferQueue

If the client sets the buffer scaling mode to freeze, then we want to
reject any buffers that do not match default width and size of the
buffer.

Additionally, we add logic to wait for the first callback before
acquiring a second buffer this is to ensure we will present the first
buffer if multiple buffers are queued in succession.

Test: atest SurfaceViewBufferTests
Bug: 168504870
Change-Id: I987f8ce4047a6f7f52726cfd404fbe9d565f83a2

libs/gui/BLASTBufferQueue.cpp

diff --git a/libs/gui/BLASTBufferQueue.cpp b/libs/gui/BLASTBufferQueue.cpp
index ba72f9b..cce434a 100644
--- a/libs/gui/BLASTBufferQueue.cpp
+++ b/libs/gui/BLASTBufferQueue.cpp
@@ -166,8 +166,8 @@
                                            const std::vector<SurfaceControlStats>& stats) {
     std::unique_lock _lock{mMutex};
     ATRACE_CALL();
-
     BQA_LOGV("transactionCallback");
+    mInitialCallbackReceived = true;
 
     if (!stats.empty()) {
         mTransformHint = stats[0].transformHint;
@@ -185,7 +185,7 @@
         if (!stats.empty()) {
             mPendingReleaseItem.releaseFence = stats[0].previousReleaseFence;
         } else {
-            ALOGE("Warning: no SurfaceControlStats returned in BLASTBufferQueue callback");
+            BQA_LOGE("Warning: no SurfaceControlStats returned in BLASTBufferQueue callback");
             mPendingReleaseItem.releaseFence = nullptr;
         }
         mBufferItemConsumer->releaseBuffer(mPendingReleaseItem.item,
@@ -198,7 +198,7 @@
     }
 
     if (mSubmitted.empty()) {
-        ALOGE("ERROR: callback with no corresponding submitted buffer item");
+        BQA_LOGE("ERROR: callback with no corresponding submitted buffer item");
     }
     mPendingReleaseItem.item = std::move(mSubmitted.front());
     mSubmitted.pop();
@@ -213,12 +213,18 @@
     ATRACE_CALL();
     BQA_LOGV("processNextBufferLocked useNextTransaction=%s", toString(useNextTransaction));
 
-    if (mNumFrameAvailable == 0 || mNumAcquired == MAX_ACQUIRED_BUFFERS + 1) {
+    // Wait to acquire a buffer if there are no frames available or we have acquired the maximum
+    // number of buffers.
+    // As a special case, we wait for the first callback before acquiring the second buffer so we
+    // can ensure the first buffer is presented if multiple buffers are queued in succession.
+    if (mNumFrameAvailable == 0 || mNumAcquired == MAX_ACQUIRED_BUFFERS + 1 ||
+        (!mInitialCallbackReceived && mNumAcquired == 1)) {
+        BQA_LOGV("processNextBufferLocked waiting for frame available or callback");
         return;
     }
 
     if (mSurfaceControl == nullptr) {
-        ALOGE("ERROR : surface control is null");
+        BQA_LOGE("ERROR : surface control is null");
         return;
     }
 
@@ -245,6 +251,13 @@
         return;
     }
 
+    if (rejectBuffer(bufferItem)) {
+        BQA_LOGE("rejecting buffer: configured width=%d, height=%d, buffer{w=%d, h=%d}", mWidth,
+                 mHeight, buffer->getWidth(), buffer->getHeight());
+        mBufferItemConsumer->releaseBuffer(bufferItem, Fence::NO_FENCE);
+        return;
+    }
+
     mNumAcquired++;
     mSubmitted.push(bufferItem);
 
@@ -311,4 +324,13 @@
     mNextTransaction = t;
 }
 
+bool BLASTBufferQueue::rejectBuffer(const BufferItem& item) const {
+    if (item.mScalingMode != NATIVE_WINDOW_SCALING_MODE_FREEZE) {
+        // Only reject buffers if scaling mode is freeze.
+        return false;
+    }
+
+    // reject buffers if the buffer size doesn't match.
+    return item.mGraphicBuffer->getWidth() != mWidth || item.mGraphicBuffer->getHeight() != mHeight;
+}
 } // namespace android