Fix browser warning and use addEventListener

[Violation] Added non-passive event listener to a scroll-blocking
event. Consider marking event handler as 'passive' to make the page more
responsive. See https://www.chromestatus.com/feature/5745543795965952

This patch also uses addEventListener instead of assigning the callback
directly to the function to be able to mark the event as passive.

Change-Id: I6c2336eed0cc4bc562fff09a08737815eaa864ce
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 8 insertions, 8 deletions

diff --git a/src/plugins/platforms/webgl/webqt.jsx b/src/plugins/platforms/webgl/webqt.jsx
index be3195a..6a4e942 100644
--- a/src/plugins/platforms/webgl/webqt.jsx
+++ b/src/plugins/platforms/webgl/webqt.jsx
@@ -267,10 +267,10 @@ window.onload = function () {
             event.returnValue = false;
         }
 
-        if ("onmousewheel" in canvas)
-            canvas.onmousewheel = handleMouseWheel;
-        else
-            canvas.addEventListener('DOMMouseScroll', handleMouseWheel, false);
+        // Internet Explorer, Opera, Chrome and Safari
+        canvas.addEventListener('mousewheel', handleMouseWheel, { passive: true });
+        // Firefox
+        canvas.addEventListener('DOMMouseScroll', handleMouseWheel, { passive: true });
 
         function handleTouch(event) {
             var object = {};
@@ -323,10 +323,10 @@ window.onload = function () {
             event.returnValue = false;
         }
 
-        canvas.addEventListener("touchstart", handleTouch, false);
-        canvas.addEventListener("touchend", handleTouch, false);
-        canvas.addEventListener("touchcancel", handleTouch, false);
-        canvas.addEventListener("touchmove", handleTouch, false);
+        canvas.addEventListener("touchstart", handleTouch, { passive: true });
+        canvas.addEventListener("touchend", handleTouch, { passive: true });
+        canvas.addEventListener("touchcancel", handleTouch, { passive: true });
+        canvas.addEventListener("touchmove", handleTouch, { passive: true });
 
         canvas.oncontextmenu = function (event) {
             event.preventDefault();