From e1599ccd3f89943a11c89ac8a31cc7d3edd72073 Mon Sep 17 00:00:00 2001
From: stuartmorgan <stuartmorgan@google.com>
Date: Mon, 20 May 2019 17:01:29 -0400
Subject: [PATCH] Fix horizontal scroll direction for macOS (#9022)

macOS uses negative values to represent scrolls to the right, while
Flutter expects the opposite, so flip X deltas.
---
 .../platform/darwin/macos/framework/Source/FLEViewController.mm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/shell/platform/darwin/macos/framework/Source/FLEViewController.mm b/shell/platform/darwin/macos/framework/Source/FLEViewController.mm
index dd7f9379f58..b061f2369ff 100644
--- a/shell/platform/darwin/macos/framework/Source/FLEViewController.mm
+++ b/shell/platform/darwin/macos/framework/Source/FLEViewController.mm
@@ -486,7 +486,7 @@ static void CommonInit(FLEViewController* controller) {
       }
     }
     double scaleFactor = self.view.layer.contentsScale;
-    flutterEvent.scroll_delta_x = event.scrollingDeltaX * pixelsPerLine * scaleFactor;
+    flutterEvent.scroll_delta_x = -event.scrollingDeltaX * pixelsPerLine * scaleFactor;
     flutterEvent.scroll_delta_y = -event.scrollingDeltaY * pixelsPerLine * scaleFactor;
   }
   FlutterEngineSendPointerEvent(_engine, &flutterEvent, 1);