From 0eff5a95bea3c0d21c6adfa468f7696853c10692 Mon Sep 17 00:00:00 2001
From: James McMullan <jpmcmu@gmail.com>
Date: Wed, 3 Dec 2014 16:47:05 -0500
Subject: [PATCH] #3992 macOS: Dragging broken in Unity

OSXScreen was not adding mouse movement deltas to mouse events while
dragging. Some 3D applications rely on these deltas to implement
dragging. Adding the mouse deltas to the mouse event fixes dragging in
these applications. Ex: Unity3d
---
 src/lib/platform/OSXScreen.mm | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/lib/platform/OSXScreen.mm b/src/lib/platform/OSXScreen.mm
index 2c2e66d6..992144e4 100644
--- a/src/lib/platform/OSXScreen.mm
+++ b/src/lib/platform/OSXScreen.mm
@@ -496,7 +496,23 @@ OSXScreen::postMouseEvent(CGPoint& pos) const
     // Fix for sticky keys
     CGEventFlags modifiers = m_keyState->getModifierStateAsOSXFlags();
     CGEventSetFlags(event, modifiers);
-    
+
+    // Set movement deltas to fix issues with certain 3D programs
+    SInt64 deltaX = pos.x;
+    deltaX -= m_xCursor;
+
+    SInt64 deltaY = pos.y;
+    deltaY -= m_yCursor;
+
+    CGEventSetIntegerValueField(event, kCGMouseEventDeltaX, deltaX);
+    CGEventSetIntegerValueField(event, kCGMouseEventDeltaY, deltaY);
+
+    double deltaFX = deltaX;
+    double deltaFY = deltaY;
+
+    CGEventSetDoubleValueField(event, kCGMouseEventDeltaX, deltaFX);
+    CGEventSetDoubleValueField(event, kCGMouseEventDeltaY, deltaFY);
+
 	CGEventPost(kCGHIDEventTap, event);
 	
 	CFRelease(event);