Allow user prevention of tap and track gestures from down

src/standard/gestures.html

@@ -73,7 +73,6 @@
   }
 
   var POINTERSTATE = {
-    tapPrevented: false,
     mouse: {
       target: null,
       mouseIgnoreJob: null
@@ -99,7 +98,6 @@
     return ta;
   }
 
-
   var Gestures = {
     gestures: {},
     recognizers: [],
@@ -252,6 +250,19 @@
       }
     },
 
+    findRecognizerByEvent: function(evName) {
+      for (var i = 0, r; i < this.recognizers.length; i++) {
+        r = this.recognizers[i];
+        for (var j = 0, n; j < r.emits.length; j++) {
+          n = r.emits[j];
+          if (n === evName) {
+            return r;
+          }
+        }
+      }
+      return null;
+    },
+
     // set scrolling direction on node to check later on first move
     // must call this before adding event listeners!
     setTouchAction: function(node, value) {
@@ -262,12 +273,27 @@
     },
 
     fire: function(target, type, detail) {
-      var ev = new CustomEvent(type, {
-        detail: detail,
+      var ev = Polymer.Base.fire(type, detail, {
+        node: target,
         bubbles: true,
         cancelable: true
       });
-      target.dispatchEvent(ev);
+
+      // forward `preventDefault` in a clean way
+      if (ev.defaultPrevented) {
+        var se = detail.sourceEvent;
+        // sourceEvent may be a touch, which is not preventable this way
+        if (se && se.preventDefault) {
+          se.preventDefault();
+        }
+      }
+    },
+
+    prevent: function(evName) {
+      var recognizer = this.findRecognizerByEvent(evName);
+      if (recognizer.info) {
+        recognizer.info.prevent = true;
+      }
     }
   };
 
@@ -293,10 +319,12 @@
       this.fire('up', e.currentTarget, e.changedTouches[0]);
     },
     fire: function(type, target, event) {
+      var self = this;
       Gestures.fire(target, type, {
         x: event.clientX,
         y: event.clientY,
-        sourceEvent: event
+        sourceEvent: event,
+        prevent: Gestures.prevent.bind(Gestures)
       });
     }
   });
@@ -318,7 +346,8 @@
           this.moves.shift();
         }
         this.moves.push(move);
-      }
+      },
+      prevent: false
     },
 
     clearInfo: function() {
@@ -327,9 +356,13 @@
       this.info.moves = [];
       this.info.x = 0;
       this.info.y = 0;
+      this.info.prevent = false;
     },
 
     hasMovedEnough: function(x, y) {
+      if (this.info.prevent) {
+        return false;
+      }
       if (this.info.started) {
         return true;
       }
@@ -348,13 +381,12 @@
           self.info.state = self.info.started ? (e.type === 'mouseup' ? 'end' : 'track') : 'start';
           self.info.addMove({x: x, y: y});
           self.fire(t, e);
-          e.preventDefault();
           self.info.started = true;
         }
       };
       var upfn = function upfn(e) {
         if (self.info.started) {
-          POINTERSTATE.tapPrevented = true;
+          Gestures.prevent('tap');
           movefn(e);
         }
         self.clearInfo();
@@ -393,7 +425,7 @@
       // only trackend if track was started and not aborted
       if (this.info.started) {
         // iff tracking, always prevent tap
-        POINTERSTATE.tapPrevented = true;
+        Gestures.prevent('tap');
         // reset started state on up
         this.info.state = 'end';
         this.info.addMove({x: ct.clientX, y: ct.clientY});
@@ -433,21 +465,22 @@
     name: 'tap',
     deps: ['mousedown', 'click', 'touchstart', 'touchend'],
     emits: ['tap'],
-    start: {
+    info: {
       x: NaN,
-      y: NaN
+      y: NaN,
+      prevent: false
     },
     reset: function() {
-      this.start.x = NaN;
-      this.start.y = NaN;
+      this.info.x = NaN;
+      this.info.y = NaN;
+      this.info.prevent = false;
     },
     save: function(e) {
-      this.start.x = e.clientX;
-      this.start.y = e.clientY;
+      this.info.x = e.clientX;
+      this.info.y = e.clientY;
     },
 
     mousedown: function(e) {
-      POINTERSTATE.tapPrevented = false;
       this.save(e);
     },
 
@@ -456,20 +489,19 @@
     },
 
     touchstart: function(e) {
-      POINTERSTATE.tapPrevented = false;
       this.save(e.changedTouches[0]);
     },
     touchend: function(e) {
       this.forward(e.changedTouches[0]);
     },
 
     forward: function(e) {
-      var dx = Math.abs(e.clientX - this.start.x);
-      var dy = Math.abs(e.clientY - this.start.y);
+      var dx = Math.abs(e.clientX - this.info.x);
+      var dy = Math.abs(e.clientY - this.info.y);
       // dx,dy can be NaN if `click` has been simulated and there was no `down` for `start`
       if (isNaN(dx) || isNaN(dy) || (dx <= TAP_DISTANCE && dy <= TAP_DISTANCE)) {
         // prevent taps from being generated if an event has canceled them
-        if (!POINTERSTATE.tapPrevented) {
+        if (!this.info.prevent) {
           Gestures.fire(e.target, 'tap', {
             x: e.clientX,
             y: e.clientY,

src/standard/utils.html

@@ -158,9 +158,10 @@
       var node = options.node || this;
       var detail = (detail === null || detail === undefined) ? Polymer.nob : detail;
       var bubbles = options.bubbles === undefined ? true : options.bubbles;
+      var cancelable = Boolean(options.cancelable);
       var event = new CustomEvent(type, {
         bubbles: Boolean(bubbles),
-        cancelable: Boolean(options.cancelable),
+        cancelable: cancelable,
         detail: detail
       });
       node.dispatchEvent(event);

test/smoke/gesture-import.html

@@ -0,0 +1,58 @@
+<link rel="import" href="../../polymer.html">
+
+<dom-module id="x-gestures">
+  <template>
+    <style>
+      #inner {
+        height: 20px;
+        width: 20px;
+        background: blue;
+      }
+      #prevent {
+        height: 20px;
+        width: 20px;
+        background: red;
+      }
+    </style>
+    <div id="prevent" on-down="preventTap"></div>
+    <a href="#" on-click="linkclick" on-touchend="removeLink">LINK</a>
+    <div id="inner" on-tap="divtap"></div>
+  </template>
+</dom-module>
+<script>
+  Polymer({
+    is: 'x-gestures',
+    listeners: {
+      'tap': 'logger',
+      'down': 'logger',
+      'up': 'logger',
+      'click': 'logger',
+      'track': 'track'
+    },
+    preventTap: function(e, detail) {
+      detail.prevent('tap');
+      detail.prevent('track');
+      e.preventDefault();
+    },
+    logger: function(e, detail) {
+      console.log(e.type);
+      console.log(detail);
+    },
+    track: function(e, detail) {
+      this.logger(e, detail);
+      if (detail.state === 'end') {
+        console.log(detail.hover());
+      }
+    },
+    linkclick: function(e) {
+      console.log('CLICK!');
+    },
+    removeLink: function(e) {
+      console.log('REMOVE!');
+      e.target.remove();
+    },
+    divtap: function(e) {
+      console.log('div tap!');
+    }
+  });
+</script>

test/smoke/gestures.html

@@ -3,7 +3,8 @@
   <head>
     <meta charset="UTF-8">
     <meta name="viewport" content="width=device-width">
-    <link rel="import" href="../../polymer.html">
+    <script src="../../../webcomponentsjs/webcomponents-lite.js"></script>
+    <link rel="import" href="gesture-import.html">
     <title>Gestures Demo</title>
     <style>
       x-gestures {
@@ -16,50 +17,5 @@
   </head>
   <body>
     <x-gestures id="host"></x-gestures>
-    <dom-module id="x-gestures">
-      <template>
-        <style>
-          #inner {
-            height: 20px;
-            width: 20px;
-            background: blue;
-          }
-        </style>
-        <a href="#" on-click="linkclick" on-touchend="removeLink">LINK</a>
-        <div id="inner" on-tap="divtap"></div>
-      </template>
-    </dom-module>
-    <script>
-      Polymer({
-        is: 'x-gestures',
-        listeners: {
-          'tap': 'logger',
-          'down': 'logger',
-          'up': 'logger',
-          'click': 'logger',
-          'track': 'track'
-        },
-        logger: function(e, detail) {
-          console.log(e.type);
-          console.log(detail);
-        },
-        track: function(e, detail) {
-          this.logger(e, detail);
-          if (detail.state === 'end') {
-            console.log(detail.hover());
-          }
-        },
-        linkclick: function(e) {
-          console.log('CLICK!');
-        },
-        removeLink: function(e) {
-          console.log('REMOVE!');
-          e.target.remove();
-        },
-        divtap: function(e) {
-          console.log('div tap!');
-        }
-      });
-    </script>
   </body>
 </html>

test/unit/gestures-elements.html

@@ -85,3 +85,29 @@
     });
   </script>
 </dom-module>
+
+<dom-module id="x-prevent">
+  <script>
+    Polymer({
+      listeners: {
+        'down': 'prevent',
+        'up': 'handle',
+        'tap': 'handle',
+        'track': 'handle'
+      },
+      is: 'x-prevent',
+      created: function() {
+        this.stream = [];
+      },
+      handle: function(e) {
+        this.stream.push(e);
+      },
+      prevent: function(e, detail) {
+        detail.prevent('tap');
+        detail.prevent('track');
+        e.preventDefault();
+        this.handle(e);
+      }
+    });
+  </script>
+</dom-module>

test/unit/gestures.html

@@ -218,8 +218,50 @@
       });
     });
 
-    // TODO(dfreedm): Add more gesture tests!
+    suite('Prevention', function() {
+      var el;
+      setup(function() {
+        el = document.createElement('x-prevent');
+        document.body.appendChild(el);
+      });
+      teardown(function() {
+        el.parentNode.removeChild(el);
+      });
 
+      test('tap', function() {
+        var ev = new CustomEvent('mousedown', {
+          bubbles: true,
+          cancelable: true
+        });
+        el.dispatchEvent(ev);
+        assert.equal(el.stream.length, 1, 'one event dispatched');
+        assert.equal(el.stream[0].type, 'down', 'was down event');
+        assert.equal(el.stream[0].defaultPrevented, true, 'was prevented');
+        assert.equal(ev.defaultPrevented, true, 'base event was prevented');
+      });
+
+      test('track', function() {
+        var ev = new CustomEvent('mousedown', {
+          bubbles: true,
+          cancelable: true
+        });
+        ev.clientX = ev.clientY = 0;
+        el.dispatchEvent(ev);
+        assert.equal(el.stream.length, 1);
+        for (var i = 0; i < 10; i++) {
+          ev = new CustomEvent(
+            i === 9 ? 'mouseup' : 'mousemove',
+            {bubbles: true, cancelable: true}
+          );
+          ev.clientX = ev.clientY = 10 * i;
+          el.dispatchEvent(ev);
+        }
+        assert.equal(el.stream.length, 2, 'expected only down and up');
+        assert.equal(el.stream[0].type, 'down', 'down was found');
+        assert.equal(el.stream[0].defaultPrevented, true, 'down was prevented');
+        assert.equal(el.stream[1].type, 'up', 'up was found');
+      });
+    });
   </script>
 
 </body>