Bug 918288 - Add logging for some of the SetTargetAPZ codepaths. r=botond

dom/ipc/TabChild.cpp

@@ -2448,6 +2448,7 @@ public:
       return;
     }
 
+    TABC_LOG("Got refresh, sending target APZCs for input block %" PRIu64 "\n", mInputBlockId);
     mTabChild->SendSetTargetAPZC(mInputBlockId, mTargets);
 
     if (!mPresShell->RemovePostRefreshObserver(this)) {
@@ -2494,21 +2495,34 @@ TabChild::SendSetTargetAPZCNotification(const WidgetTouchEvent& aEvent,
     nsIScrollableFrame* scrollAncestor = GetScrollableAncestorFrame(target);
     nsCOMPtr<dom::Element> dpElement = GetDisplayportElementFor(scrollAncestor);
 
+    nsAutoString dpElementDesc;
+    if (dpElement) {
+      dpElement->Describe(dpElementDesc);
+    }
+    TABC_LOG("For input block %" PRIu64 " found scrollable element %p (%s)\n",
+        aInputBlockId, dpElement.get(),
+        NS_LossyConvertUTF16toASCII(dpElementDesc).get());
+
     bool guidIsValid = APZCCallbackHelper::GetOrCreateScrollIdentifiers(
       dpElement, &(guid.mPresShellId), &(guid.mScrollId));
     targets.AppendElement(guid);
 
     if (guidIsValid && !nsLayoutUtils::GetDisplayPort(dpElement, nullptr)) {
+      TABC_LOG("%p didn't have a displayport, so setting one...\n", dpElement.get());
       waitForRefresh |= nsLayoutUtils::CalculateAndSetDisplayPortMargins(
         scrollAncestor, nsLayoutUtils::RepaintMode::Repaint);
     }
   }
   if (waitForRefresh) {
+    TABC_LOG("At least one target got a new displayport, need to wait for refresh\n");
     waitForRefresh = shell->AddPostRefreshObserver(
       new DisplayportSetListener(this, shell, aInputBlockId, targets));
   }
   if (!waitForRefresh) {
+    TABC_LOG("Sending target APZCs for input block %" PRIu64 "\n", aInputBlockId);
     SendSetTargetAPZC(aInputBlockId, targets);
+  } else {
+    TABC_LOG("Successfully registered post-refresh observer\n");
   }
 }
 

gfx/layers/apz/src/InputBlockState.cpp

@@ -37,6 +37,16 @@ InputBlockState::SetConfirmedTargetApzc(const nsRefPtr<AsyncPanZoomController>&
   }
   mTargetConfirmed = true;
 
+  if (mTargetApzc == aTargetApzc) {
+    // The confirmed target is the same as the tentative one, so we're done.
+    return true;
+  }
+
+  // Log enabled by default for now, we will put it in a TBS_LOG eventually
+  // once this code is more baked
+  printf_stderr("%p replacing unconfirmed target %p with real target %p\n",
+      this, mTargetApzc.get(), aTargetApzc.get());
+
   // note that aTargetApzc MAY be null here.
   mTargetApzc = aTargetApzc;
   mOverscrollHandoffChain = (mTargetApzc ? mTargetApzc->BuildOverscrollHandoffChain() : nullptr);

gfx/layers/apz/src/InputQueue.cpp

@@ -227,7 +227,8 @@ void
 InputQueue::SetConfirmedTargetApzc(uint64_t aInputBlockId, const nsRefPtr<AsyncPanZoomController>& aTargetApzc) {
   AsyncPanZoomController::AssertOnControllerThread();
 
-  INPQ_LOG("got a target apzc; block=%" PRIu64 "\n", aInputBlockId);
+  INPQ_LOG("got a target apzc; block=%" PRIu64 " guid=%s\n",
+    aInputBlockId, aTargetApzc ? Stringify(aTargetApzc->GetGuid()).c_str() : "");
   bool success = false;
   for (size_t i = 0; i < mTouchBlockQueue.Length(); i++) {
     if (mTouchBlockQueue[i]->GetBlockId() == aInputBlockId) {