Bug 788943: Allow TabParents to capture event series for faster dispatch to subprocesses. Implements capturing of touch-event series. r=smaug sr=roc

content/events/src/nsEventStateManager.cpp

@@ -1576,6 +1576,42 @@ nsEventStateManager::IsRemoteTarget(nsIContent* target) {
   return false;
 }
 
+/*static*/ void
+nsEventStateManager::MapEventCoordinatesForChildProcess(nsFrameLoader* aFrameLoader,
+                                                        nsEvent* aEvent)
+{
+  // The "toplevel widget" in child processes is always at position
+  // 0,0.  Map the event coordinates to match that.
+  nsIFrame* targetFrame = aFrameLoader->GetPrimaryFrameOfOwningContent();
+  if (!targetFrame) {
+    return;
+  }
+  nsPresContext* presContext = targetFrame->PresContext();
+
+  if (aEvent->eventStructType != NS_TOUCH_EVENT) {
+    nsPoint pt = nsLayoutUtils::GetEventCoordinatesRelativeTo(aEvent,
+                                                              targetFrame);
+    aEvent->refPoint = pt.ToNearestPixels(presContext->AppUnitsPerDevPixel());
+  } else {
+    aEvent->refPoint = nsIntPoint();
+    // Find out how far we're offset from the nearest widget.
+    nsPoint offset =
+      nsLayoutUtils::GetEventCoordinatesRelativeTo(aEvent, targetFrame);
+    nsIntPoint intOffset =
+      offset.ToNearestPixels(presContext->AppUnitsPerDevPixel());
+    nsTouchEvent* touchEvent = static_cast<nsTouchEvent*>(aEvent);
+    // Then offset all the touch points by that distance, to put them
+    // in the space where top-left is 0,0.
+    const nsTArray<nsCOMPtr<nsIDOMTouch> >& touches = touchEvent->touches;
+    for (uint32_t i = 0; i < touches.Length(); ++i) {
+      nsIDOMTouch* touch = touches[i];
+      if (touch) {
+        touch->mRefPoint += intOffset;
+      }
+    }
+  }
+}
+
 bool
 CrossProcessSafeEvent(const nsEvent& aEvent)
 {
@@ -1689,32 +1725,7 @@ nsEventStateManager::HandleCrossProcessEvent(nsEvent *aEvent,
       continue;
     }
 
-    // The "toplevel widget" in content processes is always at position
-    // 0,0.  Map the event coordinates to match that.
-    if (aEvent->eventStructType != NS_TOUCH_EVENT) {
-      nsPoint pt = nsLayoutUtils::GetEventCoordinatesRelativeTo(aEvent,
-                                                                aTargetFrame);
-      aEvent->refPoint =
-        pt.ToNearestPixels(mPresContext->AppUnitsPerDevPixel());
-    } else {
-      nsIFrame* targetFrame = frameLoader->GetPrimaryFrameOfOwningContent();
-      aEvent->refPoint = nsIntPoint();
-      // Find out how far we're offset from the nearest widget.
-      nsPoint offset =
-        nsLayoutUtils::GetEventCoordinatesRelativeTo(aEvent, targetFrame);
-      nsIntPoint intOffset =
-        offset.ToNearestPixels(mPresContext->AppUnitsPerDevPixel());
-      nsTouchEvent* touchEvent = static_cast<nsTouchEvent*>(aEvent);
-      // Then offset all the touch points by that distance, to put them
-      // in the space where top-left is 0,0.
-      const nsTArray<nsCOMPtr<nsIDOMTouch> >& touches = touchEvent->touches;
-      for (uint32_t i = 0; i < touches.Length(); ++i) {
-        nsIDOMTouch* touch = touches[i];
-        if (touch) {
-          touch->mRefPoint += intOffset;
-        }
-      }
-    }
+    MapEventCoordinatesForChildProcess(frameLoader, aEvent);
 
     dispatched |= DispatchCrossProcessEvent(aEvent, frameLoader, aStatus);
   }

content/events/src/nsEventStateManager.h

@@ -204,6 +204,9 @@ public:
 
   static bool IsRemoteTarget(nsIContent* aTarget);
 
+  static void MapEventCoordinatesForChildProcess(nsFrameLoader* aFrameLoader,
+                                                 nsEvent* aEvent);
+
   // Holds the point in screen coords that a mouse event was dispatched to,
   // before we went into pointer lock mode. This is constantly updated while
   // the pointer is not locked, but we don't update it while the pointer is

dom/ipc/TabParent.cpp

@@ -25,6 +25,7 @@
 #include "nsContentUtils.h"
 #include "nsDebug.h"
 #include "nsEventDispatcher.h"
+#include "nsEventStateManager.h"
 #include "nsFocusManager.h"
 #include "nsFrameLoader.h"
 #include "nsIContent.h"
@@ -66,6 +67,8 @@ using namespace mozilla::dom::indexedDB;
 namespace mozilla {
 namespace dom {
 
+TabParent* sEventCapturer;
+
 TabParent *TabParent::mIMETabParent = nullptr;
 
 NS_IMPL_ISUPPORTS3(TabParent, nsITabParent, nsIAuthPromptProvider, nsISecureBrowserUI)
@@ -79,6 +82,7 @@ TabParent::TabParent(mozIApplication* aApp, bool aIsBrowserElement)
   , mIMECompositionEnding(false)
   , mIMECompositionStart(0)
   , mIMESeqno(0)
+  , mEventCaptureDepth(0)
   , mDPI(0)
   , mActive(false)
   , mIsBrowserElement(aIsBrowserElement)
@@ -121,8 +125,12 @@ TabParent::Recv__delete__()
 void
 TabParent::ActorDestroy(ActorDestroyReason why)
 {
-  if (mIMETabParent == this)
+  if (sEventCapturer == this) {
+    sEventCapturer = nullptr;
+  }
+  if (mIMETabParent == this) {
     mIMETabParent = nullptr;
+  }
   nsRefPtr<nsFrameLoader> frameLoader = GetFrameLoader();
   if (frameLoader) {
     frameLoader->DestroyChild();
@@ -361,21 +369,72 @@ bool TabParent::SendRealKeyEvent(nsKeyEvent& event)
 
 bool TabParent::SendRealTouchEvent(nsTouchEvent& event)
 {
+  if (event.message == NS_TOUCH_START) {
+    MOZ_ASSERT((!sEventCapturer && mEventCaptureDepth == 0) ||
+               (sEventCapturer == this && mEventCaptureDepth > 0));
+    // We want to capture all remaining touch events in this series
+    // for fast-path dispatch.
+    sEventCapturer = this;
+    ++mEventCaptureDepth;
+  }
+
   nsTouchEvent e(event);
-  // PresShell::HandleEventInternal adds touches on touch end/cancel.
+  // PresShell::HandleEventInternal adds touches on touch end/cancel,
+  // when we're not capturing raw events from the widget backend.
   // This hack filters those out. Bug 785554
-  if (event.message == NS_TOUCH_END || event.message == NS_TOUCH_CANCEL) {
+  if (sEventCapturer != this &&
+      (event.message == NS_TOUCH_END || event.message == NS_TOUCH_CANCEL)) {
     for (int i = e.touches.Length() - 1; i >= 0; i--) {
       if (!e.touches[i]->mChanged)
         e.touches.RemoveElementAt(i);
     }
   }
+
   MaybeForwardEventToRenderFrame(event, &e);
   return (e.message == NS_TOUCH_MOVE) ?
     PBrowserParent::SendRealTouchMoveEvent(e) :
     PBrowserParent::SendRealTouchEvent(e);
 }
 
+/*static*/ TabParent*
+TabParent::GetEventCapturer()
+{
+  return sEventCapturer;
+}
+
+bool
+TabParent::TryCapture(const nsGUIEvent& aEvent)
+{
+  MOZ_ASSERT(sEventCapturer == this && mEventCaptureDepth > 0);
+
+  if (aEvent.eventStructType != NS_TOUCH_EVENT) {
+    // Only capture of touch events is implemented, for now.
+    return false;
+  }
+
+  nsTouchEvent event(static_cast<const nsTouchEvent&>(aEvent));
+
+  bool isTouchPointUp = (event.message == NS_TOUCH_END ||
+                         event.message == NS_TOUCH_CANCEL);
+  if (event.message == NS_TOUCH_START || isTouchPointUp) {
+    // Let the DOM see touch start/end events so that its touch-point
+    // state stays consistent.
+    if (isTouchPointUp && 0 == --mEventCaptureDepth) {
+      // All event series are un-captured, don't try to catch any
+      // more.
+      sEventCapturer = nullptr;
+    }
+    return false;
+  }
+
+  // Adjust the widget coordinates to be relative to our frame.
+  nsRefPtr<nsFrameLoader> frameLoader = GetFrameLoader();
+  nsEventStateManager::MapEventCoordinatesForChildProcess(frameLoader, &event);
+
+  SendRealTouchEvent(event);
+  return true;
+}
+
 bool
 TabParent::RecvSyncMessage(const nsString& aMessage,
                            const ClonedMessageData& aData,

dom/ipc/TabParent.h

@@ -66,6 +66,30 @@ public:
     mozIApplication* GetApp() { return mApp; }
     bool IsBrowserElement() { return mIsBrowserElement; }
 
+    /**
+     * Return the TabParent that has decided it wants to capture an
+     * event series for fast-path dispatch to its subprocess, if one
+     * has.
+     *
+     * DOM event dispatch and widget are free to ignore capture
+     * requests from TabParents; the end result wrt remote content is
+     * (must be) always the same, albeit usually slower without
+     * subprocess capturing.  This allows frontends/widget backends to
+     * "opt in" to faster cross-process dispatch.
+     */
+    static TabParent* GetEventCapturer();
+    /**
+     * If this is the current event capturer, give this a chance to
+     * capture the event.  If it was captured, return true, false
+     * otherwise.  Un-captured events should follow normal DOM
+     * dispatch; captured events should result in no further
+     * processing from the caller of TryCapture().
+     *
+     * It's an error to call TryCapture() if this isn't the event
+     * capturer.
+     */
+    bool TryCapture(const nsGUIEvent& aEvent);
+
     void Destroy();
 
     virtual bool RecvMoveFocus(const bool& aForward);
@@ -246,6 +270,9 @@ protected:
     uint32_t mIMECompositionStart;
     uint32_t mIMESeqno;
 
+    // The number of event series we're currently capturing.
+    int32_t mEventCaptureDepth;
+
     float mDPI;
     bool mActive;
     bool mIsBrowserElement;

widget/gonk/nsAppShell.cpp

@@ -154,7 +154,7 @@ addDOMTouch(UserInputData& data, nsTouchEvent& event, int i)
 }
 
 static nsEventStatus
-sendTouchEvent(UserInputData& data)
+sendTouchEvent(UserInputData& data, bool* captured)
 {
     uint32_t msg;
     int32_t action = data.action & AMOTION_EVENT_ACTION_MASK;
@@ -190,7 +190,7 @@ sendTouchEvent(UserInputData& data)
             addDOMTouch(data, event, i);
     }
 
-    return nsWindow::DispatchInputEvent(event);
+    return nsWindow::DispatchInputEvent(event, captured);
 }
 
 static nsEventStatus
@@ -435,7 +435,11 @@ GeckoInputDispatcher::dispatchOnce()
         nsEventStatus status = nsEventStatus_eIgnore;
         if ((data.action & AMOTION_EVENT_ACTION_MASK) !=
             AMOTION_EVENT_ACTION_HOVER_MOVE) {
-            status = sendTouchEvent(data);
+            bool captured;
+            status = sendTouchEvent(data, &captured);
+            if (captured) {
+                return;
+            }
         }
 
         uint32_t msg;

widget/gonk/nsWindow.cpp

@@ -20,6 +20,7 @@
 #include "android/log.h"
 #include "ui/FramebufferNativeWindow.h"
 
+#include "mozilla/dom/TabParent.h"
 #include "mozilla/Hal.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/FileUtils.h"
@@ -283,15 +284,30 @@ nsWindow::DoDraw(void)
 }
 
 nsEventStatus
-nsWindow::DispatchInputEvent(nsGUIEvent &aEvent)
+nsWindow::DispatchInputEvent(nsGUIEvent &aEvent, bool* aWasCaptured)
 {
-    if (!gFocusedWindow)
+    if (aWasCaptured) {
+        *aWasCaptured = false;
+    }
+    if (!gFocusedWindow) {
         return nsEventStatus_eIgnore;
+    }
 
     gFocusedWindow->UserActivity();
 
-    nsEventStatus status;
     aEvent.widget = gFocusedWindow;
+
+    if (TabParent* capturer = TabParent::GetEventCapturer()) {
+        bool captured = capturer->TryCapture(aEvent);
+        if (aWasCaptured) {
+            *aWasCaptured = captured;
+        }
+        if (captured) {
+            return nsEventStatus_eConsumeNoDefault;
+        }
+    }
+
+    nsEventStatus status;
     gFocusedWindow->DispatchEvent(&aEvent, status);
     return status;
 }

widget/gonk/nsWindow.h

@@ -46,7 +46,8 @@ public:
     virtual ~nsWindow();
 
     static void DoDraw(void);
-    static nsEventStatus DispatchInputEvent(nsGUIEvent &aEvent);
+    static nsEventStatus DispatchInputEvent(nsGUIEvent &aEvent,
+                                            bool* aWasCaptured = nullptr);
 
     NS_IMETHOD Create(nsIWidget *aParent,
                       void *aNativeParent,