commit 7143316af216fa92c31a60d4407b707637382da1
author Dan Stoza <stoza@google.com> Tue Feb 04 16:22:36 2014 -0800
committer Dan Stoza <stoza@google.com> Tue Feb 04 16:46:54 2014 -0800
tree 947490d7fc78fe0897dee344f972107fd3423166
parent 1d41d5d82c0654313b33d45c7b8943eeba13469e

Fix virtual display nesting

This fixes the cycling rendering loop caused by nesting virtual
displays by preventing them from recomposing if their contents
haven't changed.

Bug: 12101046
Change-Id: I600365c0fd5d3ad93e04295d26cf9de177ffc79b

services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp

diff --git a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
index d7fef8c..a1820ab 100644
--- a/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
+++ b/services/surfaceflinger/DisplayHardware/VirtualDisplaySurface.cpp
@@ -56,7 +56,8 @@
     mOutputUsage(GRALLOC_USAGE_HW_COMPOSER),
     mProducerSlotSource(0),
     mDbgState(DBG_STATE_IDLE),
-    mDbgLastCompositionType(COMPOSITION_UNKNOWN)
+    mDbgLastCompositionType(COMPOSITION_UNKNOWN),
+    mMustRecompose(false)
 {
     mSource[SOURCE_SINK] = sink;
     mSource[SOURCE_SCRATCH] = bq;
@@ -92,10 +93,12 @@
 VirtualDisplaySurface::~VirtualDisplaySurface() {
 }
 
-status_t VirtualDisplaySurface::beginFrame() {
+status_t VirtualDisplaySurface::beginFrame(bool mustRecompose) {
     if (mDisplayId < 0)
         return NO_ERROR;
 
+    mMustRecompose = mustRecompose;
+
     VDS_LOGW_IF(mDbgState != DBG_STATE_IDLE,
             "Unexpected beginFrame() in %s state", dbgStateStr());
     mDbgState = DBG_STATE_BEGUN;
@@ -228,16 +231,24 @@
         QueueBufferOutput qbo;
         sp<Fence> outFence = mHwc.getLastRetireFence(mDisplayId);
         VDS_LOGV("onFrameCommitted: queue sink sslot=%d", sslot);
-        status_t result = mSource[SOURCE_SINK]->queueBuffer(sslot,
-                QueueBufferInput(
-                    systemTime(), false /* isAutoTimestamp */,
-                    Rect(mSinkBufferWidth, mSinkBufferHeight),
-                    NATIVE_WINDOW_SCALING_MODE_FREEZE, 0 /* transform */,
-                    true /* async*/,
-                    outFence),
-                &qbo);
-        if (result == NO_ERROR) {
-            updateQueueBufferOutput(qbo);
+        if (mMustRecompose) {
+            status_t result = mSource[SOURCE_SINK]->queueBuffer(sslot,
+                    QueueBufferInput(
+                        systemTime(), false /* isAutoTimestamp */,
+                        Rect(mSinkBufferWidth, mSinkBufferHeight),
+                        NATIVE_WINDOW_SCALING_MODE_FREEZE, 0 /* transform */,
+                        true /* async*/,
+                        outFence),
+                    &qbo);
+            if (result == NO_ERROR) {
+                updateQueueBufferOutput(qbo);
+            }
+        } else {
+            // If the surface hadn't actually been updated, then we only went
+            // through the motions of updating the display to keep our state
+            // machine happy. We cancel the buffer to avoid triggering another
+            // re-composition and causing an infinite loop.
+            mSource[SOURCE_SINK]->cancelBuffer(sslot, outFence);
         }
     }