diff --git a/src/lib/settings.html b/src/lib/settings.html
index 09b2a11576..41f138add1 100644
--- a/src/lib/settings.html
+++ b/src/lib/settings.html
@@ -57,6 +57,8 @@
settings.isIE = navigator.userAgent.match('Trident');
+ settings.passiveTouchGestures = settings.passiveTouchGestures || false;
+
return settings;
})()
};
diff --git a/src/standard/gestures.html b/src/standard/gestures.html
index 63c9a9cdbb..6cb235f9b8 100644
--- a/src/standard/gestures.html
+++ b/src/standard/gestures.html
@@ -38,6 +38,14 @@
}
})();
+ /**
+ * @param {string} name Possible mouse event name
+ * @return {boolean} true if mouse event, false if not
+ */
+ function isMouseEvent(name) {
+ return MOUSE_EVENTS.indexOf(name) > -1;
+ }
+
/* eslint no-empty: ["error", { "allowEmptyCatch": true }] */
// check for passive event listeners
var SUPPORTS_PASSIVE = false;
@@ -49,6 +57,13 @@
} catch(e) {}
})();
+ // decide whether to use {passive: true} for gestures listening for touch events
+ function PASSIVE_TOUCH() {
+ if (HAS_NATIVE_TA && SUPPORTS_PASSIVE && Polymer.Settings.passiveTouchGestures) {
+ return {passive: true};
+ }
+ }
+
// Check for touch-only devices
var IS_TOUCH_ONLY = navigator.userAgent.match(/iP(?:[oa]d|hone)|Android/);
@@ -110,7 +125,7 @@
function hasLeftMouseButton(ev) {
var type = ev.type;
// exit early if the event is not a mouse event
- if (MOUSE_EVENTS.indexOf(type) === -1) {
+ if (!isMouseEvent(type)) {
return false;
}
// ev.button is not reliable for mousemove (0 is overloaded as both left button and no buttons)
@@ -326,7 +341,7 @@
for (var i = 0, dep, gd; i < deps.length; i++) {
dep = deps[i];
// don't add mouse handlers on iOS because they cause gray selection overlays
- if (IS_TOUCH_ONLY && MOUSE_EVENTS.indexOf(dep) > -1 && dep !== 'click') {
+ if (IS_TOUCH_ONLY && isMouseEvent(dep) && dep !== 'click') {
continue;
}
gd = gobj[dep];
@@ -334,7 +349,8 @@
gobj[dep] = gd = {_count: 0};
}
if (gd._count === 0) {
- node.addEventListener(dep, this.handleNative);
+ var options = !isMouseEvent(dep) && PASSIVE_TOUCH();
+ node.addEventListener(dep, this.handleNative, options);
}
gd[name] = (gd[name] || 0) + 1;
gd._count = (gd._count || 0) + 1;
@@ -361,7 +377,8 @@
gd[name] = (gd[name] || 1) - 1;
gd._count = (gd._count || 1) - 1;
if (gd._count === 0) {
- node.removeEventListener(dep, this.handleNative);
+ var options = !isMouseEvent(dep) && PASSIVE_TOUCH();
+ node.removeEventListener(dep, this.handleNative, options);
}
}
}
diff --git a/test/smoke/passive-gestures.html b/test/smoke/passive-gestures.html
new file mode 100644
index 0000000000..5fa22bd471
--- /dev/null
+++ b/test/smoke/passive-gestures.html
@@ -0,0 +1,53 @@
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
\ No newline at end of file