Bug 1018639 - Maintain separate cursors in chrome and client processes. r=roc

The TabChild now maintains a concept of the current cursor for the child
process.  This value is asynchronously cached in the TabParent.  The
chrome process now establishes cursor on its own - consulting the
TabParent when the cursor enters/exits the tab.  While the cursor is
over tab content, changes to the TabParent's cached cursor are
immediately forwarded to the widget.

dom/events/EventStateManager.cpp

@@ -1180,7 +1180,9 @@ CrossProcessSafeEvent(const WidgetEvent& aEvent)
     case NS_MOUSE_BUTTON_UP:
     case NS_MOUSE_MOVE:
     case NS_CONTEXTMENU:
+    case NS_MOUSE_ENTER:
     case NS_MOUSE_EXIT:
+    case NS_MOUSE_ENTER_SYNTH:
       return true;
     default:
       return false;
@@ -3787,20 +3789,27 @@ EventStateManager::DispatchMouseOrPointerEvent(WidgetMouseEvent* aMouseEvent,
     // the same object after event dispatch and handling, so refetch it.
     targetFrame = mPresContext->GetPrimaryFrameFor(aTargetContent);
 
-    // If we are leaving remote content, dispatch a mouse exit event to the
-    // remote frame.
-    if (aMessage == NS_MOUSE_EXIT_SYNTH && IsRemoteTarget(aTargetContent)) {
-      // For remote content, send a normal widget mouse exit event.
-      nsAutoPtr<WidgetMouseEvent> remoteEvent;
-      CreateMouseOrPointerWidgetEvent(aMouseEvent, NS_MOUSE_EXIT,
-                                      aRelatedContent, remoteEvent);
+    // If we are entering/leaving remote content, dispatch a mouse enter/exit
+    // event to the remote frame.
+    if (IsRemoteTarget(aTargetContent)) {
+      if (aMessage == NS_MOUSE_EXIT_SYNTH) {
+        // For remote content, send a normal widget mouse exit event.
+        nsAutoPtr<WidgetMouseEvent> remoteEvent;
+        CreateMouseOrPointerWidgetEvent(aMouseEvent, NS_MOUSE_EXIT,
+                                        aRelatedContent, remoteEvent);
 
-      // mCurrentTarget is set to the new target, so we must reset it to the
-      // old target and then dispatch a cross-process event. (mCurrentTarget
-      // will be set back below.) HandleCrossProcessEvent will query for the
-      // proper target via GetEventTarget which will return mCurrentTarget.
-      mCurrentTarget = targetFrame;
-      HandleCrossProcessEvent(remoteEvent, &status);
+        // mCurrentTarget is set to the new target, so we must reset it to the
+        // old target and then dispatch a cross-process event. (mCurrentTarget
+        // will be set back below.) HandleCrossProcessEvent will query for the
+        // proper target via GetEventTarget which will return mCurrentTarget.
+        mCurrentTarget = targetFrame;
+        HandleCrossProcessEvent(remoteEvent, &status);
+      } else if (aMessage == NS_MOUSE_ENTER_SYNTH) {
+        nsAutoPtr<WidgetMouseEvent> remoteEvent;
+        CreateMouseOrPointerWidgetEvent(aMouseEvent, NS_MOUSE_ENTER,
+                                        aRelatedContent, remoteEvent);
+        HandleCrossProcessEvent(remoteEvent, &status);
+      }
     }
   }
 

dom/ipc/TabParent.cpp

@@ -283,6 +283,8 @@ TabParent::TabParent(nsIContentParent* aManager,
   , mTabId(aTabId)
   , mCreatingWindow(false)
   , mNeedLayerTreeReadyNotification(false)
+  , mCursor(nsCursor(-1))
+  , mTabSetsCursor(false)
 {
   MOZ_ASSERT(aManager);
 }
@@ -1168,6 +1170,25 @@ bool TabParent::SendRealMouseEvent(WidgetMouseEvent& event)
     return false;
   }
   event.refPoint += GetChildProcessOffset();
+
+  nsCOMPtr<nsIWidget> widget = GetWidget();
+  if (widget) {
+    // When we mouseenter the tab, the tab's cursor should become the current
+    // cursor.  When we mouseexit, we stop.
+    if (event.message == NS_MOUSE_ENTER ||
+        event.message == NS_MOUSE_ENTER_SYNTH) {
+      mTabSetsCursor = true;
+      if (mCursor != nsCursor(-1)) {
+        widget->SetCursor(mCursor);
+      }
+      // We don't actually want to forward NS_MOUSE_ENTER messages.
+      return true;
+    } else if (event.message == NS_MOUSE_EXIT ||
+               event.message == NS_MOUSE_EXIT_SYNTH) {
+      mTabSetsCursor = false;
+    }
+  }
+
   if (event.message == NS_MOUSE_MOVE) {
     return SendRealMouseMoveEvent(event);
   }
@@ -1636,12 +1657,16 @@ TabParent::RecvAsyncMessage(const nsString& aMessage,
 bool
 TabParent::RecvSetCursor(const uint32_t& aCursor, const bool& aForce)
 {
+  mCursor = static_cast<nsCursor>(aCursor);
+
   nsCOMPtr<nsIWidget> widget = GetWidget();
   if (widget) {
     if (aForce) {
       widget->ClearCachedCursor();
     }
-    widget->SetCursor((nsCursor) aCursor);
+    if (mTabSetsCursor) {
+      widget->SetCursor(mCursor);
+    }
   }
   return true;
 }

dom/ipc/TabParent.h

@@ -25,13 +25,13 @@
 #include "nsIXULBrowserWindow.h"
 #include "nsWeakReference.h"
 #include "Units.h"
+#include "nsIWidget.h"
 
 class nsFrameLoader;
 class nsIFrameLoader;
 class nsIContent;
 class nsIPrincipal;
 class nsIURI;
-class nsIWidget;
 class nsILoadContext;
 class nsIDocShell;
 
@@ -587,6 +587,14 @@ private:
     // again once the RenderFrameParent arrives.
     bool mNeedLayerTreeReadyNotification;
 
+    // Cached cursor setting from TabChild.  When the cursor is over the tab,
+    // it should take this appearance.
+    nsCursor mCursor;
+
+    // True if the cursor changes from the TabChild should change the widget
+    // cursor.  This happens whenever the cursor is in the tab's region.
+    bool mTabSetsCursor;
+
 private:
     // This is used when APZ needs to find the TabParent associated with a layer
     // to dispatch events.