From 989e86074aeb339075c617ac788ec84d441db62f Mon Sep 17 00:00:00 2001
From: Lorn Potter <lorn.potter@gmail.com>
Date: Fri, 29 Jun 2018 11:08:27 +1000
Subject: wasm: use config for natural scroll on safari
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Change-Id: Idc2ee096144194e3f0d9ca165a578ff9745ef13d
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
---
 .../platforms/wasm/qwasmeventtranslator.cpp        | 29 ++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
index 95bedf701c..cc48c15b64 100644
--- a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
+++ b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
@@ -39,15 +39,27 @@
 #include <QtCore/qobject.h>
 
 #include <QtCore/qdeadlinetimer.h>
+#include <emscripten/bind.h>
 
 #include <iostream>
 
 QT_BEGIN_NAMESPACE
+using namespace emscripten;
 
 // macOS CTRL <-> META switching. We most likely want to enable
 // the existing switching code in QtGui, but for now do it here.
 static bool g_usePlatformMacCtrlMetaSwitching = false;
 
+bool g_useNaturalScrolling = false;
+
+void setNaturalScrolling(bool use) {
+    g_useNaturalScrolling = use;
+}
+
+EMSCRIPTEN_BINDINGS(mouse_module) {
+    function("setNaturalScrolling", &setNaturalScrolling);
+}
+
 QWasmEventTranslator::QWasmEventTranslator(QObject *parent)
     : QObject(parent)
     , draggedWindow(nullptr)
@@ -84,6 +96,20 @@ QWasmEventTranslator::QWasmEventTranslator(QObject *parent)
         Platform(EM_ASM_INT("if (navigator.platform.includes(\"Mac\")) return 1; return 0;"));
 
     g_usePlatformMacCtrlMetaSwitching = (platform == MacOSPlatform);
+
+    if (platform == MacOSPlatform) {
+        g_useNaturalScrolling = true; //make this default on macOS
+        EM_ASM(
+            if (window.safari !== undefined)  {//this only works on safari
+                Module["canvas"].addEventListener('wheel', mouseWheelEvent);
+                function mouseWheelEvent(e) {
+                    if (event.webkitDirectionInvertedFromDevice) {
+                        Module.setNaturalScrolling(event.webkitDirectionInvertedFromDevice);
+                    }
+                }
+            }
+        );
+    }
 }
 
 template <typename Event>
@@ -449,6 +475,9 @@ int QWasmEventTranslator::wheel_cb(int eventType, const EmscriptenWheelEvent *wh
         break;
     };
 
+    if (g_useNaturalScrolling) //macOS platform has document oriented scrolling
+        scrollFactor = -scrollFactor;
+
     Qt::KeyboardModifiers modifiers = translateMouseEventModifier(&mouseEvent);
     auto timestamp = mouseEvent.timestamp;
     QPoint globalPoint(mouseEvent.canvasX, mouseEvent.canvasY);
-- 
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