From 274c9d4c174a5c127776e7e4ab17a46237351f5e Mon Sep 17 00:00:00 2001
From: David Anderson <danderson@mozilla.com>
Date: Thu, 26 Mar 2015 14:23:02 -0700
Subject: [PATCH] Allow dispatching to the APZ controller thread from any
 thread. (bug 1147681 part 1, r=kats)

--HG--
extra : rebase_source : ce0beebda151fdf5adf69e998465c684b193db75
---
 gfx/layers/apz/util/APZThreadUtils.cpp | 44 +++++++++++---------------
 gfx/layers/apz/util/APZThreadUtils.h   |  5 +++
 widget/gonk/nsWindow.cpp               |  6 ++++
 widget/gonk/nsWindow.h                 |  2 ++
 widget/nsBaseWidget.cpp                |  8 +++++
 widget/nsBaseWidget.h                  |  1 +
 6 files changed, 41 insertions(+), 25 deletions(-)

diff --git a/gfx/layers/apz/util/APZThreadUtils.cpp b/gfx/layers/apz/util/APZThreadUtils.cpp
index 1c9c5eb6e05f..9c4ddc35a2f3 100644
--- a/gfx/layers/apz/util/APZThreadUtils.cpp
+++ b/gfx/layers/apz/util/APZThreadUtils.cpp
@@ -11,7 +11,7 @@ namespace mozilla {
 namespace layers {
 
 static bool sThreadAssertionsEnabled = true;
-static PRThread* sControllerThread;
+static MessageLoop* sControllerThread;
 
 /*static*/ void
 APZThreadUtils::SetThreadAssertionsEnabled(bool aEnabled) {
@@ -23,22 +23,22 @@ APZThreadUtils::GetThreadAssertionsEnabled() {
   return sThreadAssertionsEnabled;
 }
 
+/*static*/ void
+APZThreadUtils::SetControllerThread(MessageLoop* aLoop)
+{
+  // We must either be setting the initial controller thread, or removing it,
+  // or re-using an existing controller thread.
+  MOZ_ASSERT(!sControllerThread || !aLoop || sControllerThread == aLoop);
+  sControllerThread = aLoop;
+}
+
 /*static*/ void
 APZThreadUtils::AssertOnControllerThread() {
   if (!GetThreadAssertionsEnabled()) {
     return;
   }
 
-  static bool sControllerThreadDetermined = false;
-  if (!sControllerThreadDetermined) {
-    // Technically this may not actually pick up the correct controller thread,
-    // if the first call to this method happens from a non-controller thread.
-    // If the assertion below fires, it is possible that it is because
-    // sControllerThread is not actually the controller thread.
-    sControllerThread = PR_GetCurrentThread();
-    sControllerThreadDetermined = true;
-  }
-  MOZ_ASSERT(sControllerThread == PR_GetCurrentThread());
+  MOZ_ASSERT(sControllerThread == MessageLoop::current());
 }
 
 /*static*/ void
@@ -52,25 +52,19 @@ APZThreadUtils::AssertOnCompositorThread()
 /*static*/ void
 APZThreadUtils::RunOnControllerThread(Task* aTask)
 {
-#ifdef MOZ_WIDGET_GONK
-  // On B2G the controller thread is the compositor thread, and this function
-  // is always called from the libui thread or the main thread.
-  MessageLoop* loop = CompositorParent::CompositorLoop();
-  if (!loop) {
+  if (!sControllerThread) {
     // Could happen on startup
     NS_WARNING("Dropping task posted to controller thread\n");
     delete aTask;
     return;
   }
-  MOZ_ASSERT(MessageLoop::current() != loop);
-  loop->PostTask(FROM_HERE, aTask);
-#else
-  // On non-B2G platforms this is only ever called from the controller thread
-  // itself.
-  AssertOnControllerThread();
-  aTask->Run();
-  delete aTask;
-#endif
+
+  if (sControllerThread == MessageLoop::current()) {
+    aTask->Run();
+    delete aTask;
+  } else {
+    sControllerThread->PostTask(FROM_HERE, aTask);
+  }
 }
 
 } // namespace layers
diff --git a/gfx/layers/apz/util/APZThreadUtils.h b/gfx/layers/apz/util/APZThreadUtils.h
index 2bb37979e954..4b3ebc425455 100644
--- a/gfx/layers/apz/util/APZThreadUtils.h
+++ b/gfx/layers/apz/util/APZThreadUtils.h
@@ -22,6 +22,11 @@ public:
   static void SetThreadAssertionsEnabled(bool aEnabled);
   static bool GetThreadAssertionsEnabled();
 
+  /**
+   * Set the controller thread.
+   */
+  static void SetControllerThread(MessageLoop* aLoop);
+
   /**
    * This can be used to assert that the current thread is the
    * controller/UI thread (on which input events are received).
diff --git a/widget/gonk/nsWindow.cpp b/widget/gonk/nsWindow.cpp
index e50a40184893..9d346d998842 100644
--- a/widget/gonk/nsWindow.cpp
+++ b/widget/gonk/nsWindow.cpp
@@ -227,6 +227,12 @@ nsWindow::DoDraw(void)
     }
 }
 
+void
+nsWindow::ConfigureAPZControllerThread()
+{
+  APZThreadUtils::SetControllerThread(CompositorParent::CompositorLoop());
+}
+
 /*static*/ nsEventStatus
 nsWindow::DispatchInputEvent(WidgetGUIEvent& aEvent)
 {
diff --git a/widget/gonk/nsWindow.h b/widget/gonk/nsWindow.h
index 8b3b38e6a34a..7bd373b808f1 100644
--- a/widget/gonk/nsWindow.h
+++ b/widget/gonk/nsWindow.h
@@ -132,6 +132,8 @@ public:
 
     virtual Composer2D* GetComposer2D() override;
 
+    void ConfigureAPZControllerThread() override;
+
 protected:
     nsWindow* mParent;
     bool mVisible;
diff --git a/widget/nsBaseWidget.cpp b/widget/nsBaseWidget.cpp
index bcd2ce14dde5..dbffe2ea34d0 100644
--- a/widget/nsBaseWidget.cpp
+++ b/widget/nsBaseWidget.cpp
@@ -978,6 +978,8 @@ void nsBaseWidget::ConfigureAPZCTreeManager()
   mAPZC = CompositorParent::GetAPZCTreeManager(rootLayerTreeId);
   MOZ_ASSERT(mAPZC);
 
+  ConfigureAPZControllerThread();
+
   mAPZC->SetDPI(GetDPI());
   mAPZEventState = new APZEventState(this,
       new ChromeProcessContentReceivedInputBlockCallback(mAPZC));
@@ -990,6 +992,12 @@ void nsBaseWidget::ConfigureAPZCTreeManager()
   }
 }
 
+void nsBaseWidget::ConfigureAPZControllerThread()
+{
+  // By default the controller thread is the main thread.
+  APZThreadUtils::SetControllerThread(MessageLoop::current());
+}
+
 nsEventStatus
 nsBaseWidget::ProcessUntransformedAPZEvent(WidgetInputEvent* aEvent,
                                            const ScrollableLayerGuid& aGuid,
diff --git a/widget/nsBaseWidget.h b/widget/nsBaseWidget.h
index 3a2a0000c298..269547d3a600 100644
--- a/widget/nsBaseWidget.h
+++ b/widget/nsBaseWidget.h
@@ -331,6 +331,7 @@ protected:
                              nsWidgetInitData *aInitData);
 
   virtual void ConfigureAPZCTreeManager();
+  virtual void ConfigureAPZControllerThread();
   virtual already_AddRefed<GeckoContentController> CreateRootContentController();
 
   // Dispatch an event that has already been routed through APZ.