Bug 1161206 - Implement native mousewheel event synthesization on OS X. r=mstange

dom/interfaces/base/nsIDOMWindowUtils.idl

@@ -51,7 +51,7 @@ interface nsIJSRAIIHelper;
 interface nsIContentPermissionRequest;
 interface nsIObserver;
 
-[scriptable, uuid(9bb4a34f-de8f-43d3-a58c-10757cac95a0)]
+[scriptable, uuid(1a75c351-d115-4d51-94df-731dd1723a1f)]
 interface nsIDOMWindowUtils : nsISupports {
 
   /**
@@ -613,6 +613,11 @@ interface nsIDOMWindowUtils : nsISupports {
    */
   const unsigned long MOUSESCROLL_PREFER_WIDGET_AT_POINT = 0x00000001;
 
+  /**
+   * Interpret the scroll delta values as lines rather than pixels.
+   */
+  const unsigned long MOUSESCROLL_SCROLL_LINES = 0x00000002;
+
   /**
    * The platform specific values of aAdditionalFlags.  Must be over 0x00010000.
    */

widget/cocoa/nsChildView.h

@@ -466,6 +466,14 @@ public:
   virtual nsresult SynthesizeNativeMouseMove(mozilla::LayoutDeviceIntPoint aPoint,
                                              nsIObserver* aObserver) override
   { return SynthesizeNativeMouseEvent(aPoint, NSMouseMoved, 0, aObserver); }
+  virtual nsresult SynthesizeNativeMouseScrollEvent(mozilla::LayoutDeviceIntPoint aPoint,
+                                                    uint32_t aNativeMessage,
+                                                    double aDeltaX,
+                                                    double aDeltaY,
+                                                    double aDeltaZ,
+                                                    uint32_t aModifierFlags,
+                                                    uint32_t aAdditionalFlags,
+                                                    nsIObserver* aObserver) override;
 
   // Mac specific methods
   

widget/cocoa/nsChildView.mm

@@ -91,6 +91,7 @@
 #include "InputData.h"
 #include "VibrancyManager.h"
 #include "nsNativeThemeCocoa.h"
+#include "nsIDOMWindowUtils.h"
 
 using namespace mozilla;
 using namespace mozilla::layers;
@@ -1185,6 +1186,42 @@ nsresult nsChildView::SynthesizeNativeMouseEvent(LayoutDeviceIntPoint aPoint,
   NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
 }
 
+nsresult nsChildView::SynthesizeNativeMouseScrollEvent(mozilla::LayoutDeviceIntPoint aPoint,
+                                                       uint32_t aNativeMessage,
+                                                       double aDeltaX,
+                                                       double aDeltaY,
+                                                       double aDeltaZ,
+                                                       uint32_t aModifierFlags,
+                                                       uint32_t aAdditionalFlags,
+                                                       nsIObserver* aObserver)
+{
+  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
+
+  AutoObserverNotifier notifier(aObserver, "mousescrollevent");
+
+  NSPoint pt =
+    nsCocoaUtils::DevPixelsToCocoaPoints(aPoint, BackingScaleFactor());
+
+  // Move the mouse cursor to the requested position and reconnect it to the mouse.
+  CGWarpMouseCursorPosition(NSPointToCGPoint(pt));
+  CGAssociateMouseAndMouseCursorPosition(true);
+
+  // Mostly copied from http://stackoverflow.com/a/6130349
+  CGScrollEventUnit units =
+    (aAdditionalFlags & nsIDOMWindowUtils::MOUSESCROLL_SCROLL_LINES)
+    ? kCGScrollEventUnitLine : kCGScrollEventUnitPixel;
+  CGEventRef cgEvent = CGEventCreateScrollWheelEvent(NULL, units, 3, aDeltaY, aDeltaX, aDeltaZ);
+  if (!cgEvent) {
+    return NS_ERROR_FAILURE;
+  }
+
+  CGEventPost(kCGHIDEventTap, cgEvent);
+  CFRelease(cgEvent);
+  return NS_OK;
+
+  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
+}
+
 // First argument has to be an NSMenu representing the application's top-level
 // menu bar. The returned item is *not* retained.
 static NSMenuItem* NativeMenuItemWithLocation(NSMenu* menubar, NSString* locationString)