commit 076acace33a13f588d3e7450872e738bc1fa3f06
author Chavi Weingarten <chaviw@google.com> Thu Jan 19 17:20:43 2023 +0000
committer Chavi Weingarten <chaviw@google.com> Mon Jan 23 20:18:52 2023 +0000
tree 08008dc100deee526362459413f335bb8540f1ee
parent 39bf1d612d52c444f3e28f399f688e5b2f6d74ab

SurfaceFlinger: Add TrustedPresentationListener API

TrustedPresentationListener is intended to allow the producer
of a buffer layer to gain a trusted signal on whether and to
what extent a layer is presented. A strawman design would be to
provide the producer details on it's presentation (alpha,
position, scale, final crop, covered region, etc). In the strawman
design the client end would then decide itself whether each of these
parameters were in an acceptable range.

However providing the client feedback on it's per frame position would have
a negative system health impact. Furthermore in some of the target use cases
we can't even be sure the layer of interest is actively producing buffers
and so there may be no existing callback to piggy-back on.

Because of this we use a server side thresholding approach, where the client
expresses some visibility threshold and a time stability constraint. See
SurfaceComposerClient.h comment for details on these thresholds and their
computation.

Bug: 256993331
Test: LayerTrustedPresentationListener_test.cpp
Change-Id: If4bef60dc6b22ce4959c353fa2a19b0994a00f5c

libs/gui/LayerState.cpp

diff --git a/libs/gui/LayerState.cpp b/libs/gui/LayerState.cpp
index 59b62fe..43acb16 100644
--- a/libs/gui/LayerState.cpp
+++ b/libs/gui/LayerState.cpp
@@ -185,6 +185,8 @@
     if (hasBufferData) {
         SAFE_PARCEL(output.writeParcelable, *bufferData);
     }
+    SAFE_PARCEL(output.writeParcelable, trustedPresentationThresholds);
+    SAFE_PARCEL(output.writeParcelable, trustedPresentationListener);
     return NO_ERROR;
 }
 
@@ -315,6 +317,10 @@
     } else {
         bufferData = nullptr;
     }
+
+    SAFE_PARCEL(input.readParcelable, &trustedPresentationThresholds);
+    SAFE_PARCEL(input.readParcelable, &trustedPresentationListener);
+
     return NO_ERROR;
 }
 
@@ -553,6 +559,11 @@
         what |= eBufferChanged;
         bufferData = other.bufferData;
     }
+    if (other.what & eTrustedPresentationInfoChanged) {
+        what |= eTrustedPresentationInfoChanged;
+        trustedPresentationListener = other.trustedPresentationListener;
+        trustedPresentationThresholds = other.trustedPresentationThresholds;
+    }
     if (other.what & eDataspaceChanged) {
         what |= eDataspaceChanged;
         dataspace = other.dataspace;
@@ -998,4 +1009,20 @@
     return NO_ERROR;
 }
 
+status_t TrustedPresentationListener::writeToParcel(Parcel* parcel) const {
+    SAFE_PARCEL(parcel->writeStrongBinder, callbackInterface);
+    SAFE_PARCEL(parcel->writeInt32, callbackId);
+    return NO_ERROR;
+}
+
+status_t TrustedPresentationListener::readFromParcel(const Parcel* parcel) {
+    sp<IBinder> tmpBinder = nullptr;
+    SAFE_PARCEL(parcel->readNullableStrongBinder, &tmpBinder);
+    if (tmpBinder) {
+        callbackInterface = checked_interface_cast<ITransactionCompletedListener>(tmpBinder);
+    }
+    SAFE_PARCEL(parcel->readInt32, &callbackId);
+    return NO_ERROR;
+}
+
 }; // namespace android