Bug 1289435 - Support native event synthesization even for non-touch windows devices. r=jimm

MozReview-Commit-ID: IeHmDOiWOW2

widget/windows/nsWindowBase.cpp

@@ -128,7 +128,25 @@ nsWindowBase::SynthesizeNativeTouchPoint(uint32_t aPointerId,
   AutoObserverNotifier notifier(aObserver, "touchpoint");
 
   if (!InitTouchInjection()) {
-    return NS_ERROR_NOT_IMPLEMENTED;
+    // If we don't have touch injection from the OS, we can just fake it and
+    // synthesize the events from here.
+    MOZ_ASSERT(NS_IsMainThread());
+    if (aPointerState == TOUCH_HOVER) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    if (!mSynthesizedTouchInput) {
+      mSynthesizedTouchInput = MakeUnique<MultiTouchInput>();
+    }
+
+    WidgetEventTime time = CurrentMessageWidgetEventTime();
+    LayoutDeviceIntPoint pointInWindow = aPoint - WidgetToScreenOffset();
+    MultiTouchInput inputToDispatch = UpdateSynthesizedTouchState(
+        mSynthesizedTouchInput.get(), time.mTime, time.mTimeStamp,
+        aPointerId, aPointerState, pointInWindow, aPointerPressure,
+        aPointerOrientation);
+    DispatchTouchInput(inputToDispatch);
+    return NS_OK;
   }
 
   bool hover = aPointerState & TOUCH_HOVER;

widget/windows/nsWindowBase.h

@@ -129,6 +129,10 @@ protected:
   static bool sTouchInjectInitialized;
   static InjectTouchInputPtr sInjectTouchFuncPtr;
 
+  // This is used by SynthesizeNativeTouchPoint to maintain state between
+  // multiple synthesized points, in the case where we can't call InjectTouch
+  // directly.
+  mozilla::UniquePtr<mozilla::MultiTouchInput> mSynthesizedTouchInput;
 protected:
   InputContext mInputContext;
 };