Fix more issues with tracking multiple pointers.

src/mousetracker.js

@@ -317,6 +317,20 @@
             return this;
         },
 
+        /**
+         * Returns {Array.<OpenSeadragon.MouseTracker>} excluding the given pointer device type
+         * @function
+         * @param {String} type - The pointer device type: "mouse", "touch", "pen", etc.
+         * @returns {Array.<OpenSeadragon.MouseTracker>}
+         */
+        getActivePointersListExceptType: function ( type ) {
+            var delegate = THIS[ this.hash ];
+
+            return delegate.activePointersLists.filter(function(pointersList) {
+                return pointersList.type !== type;
+            });
+        },
+
         /**
          * Returns the {@link OpenSeadragon.MouseTracker.GesturePointList|GesturePointList} for the given pointer device type,
          * creating and caching a new {@link OpenSeadragon.MouseTracker.GesturePointList|GesturePointList} if one doesn't already exist for the type.
@@ -1201,6 +1215,30 @@
                 }
             }
             return null;
+        },
+
+        /**
+         * @function Increment this pointer's contact count.
+         * It will evaluate whether this pointer type is allowed to have multiple contacts.
+         */
+        addContact: function() {
+            ++this.contacts;
+
+            if (this.contacts > 1 && (this.type === "mouse" || this.type === "pen")) {
+                this.contacts = 1;
+            }
+        },
+
+        /**
+         * @function Decrement this pointer's contact count.
+         * It will make sure the count does not go below 0.
+         */
+        removeContact: function() {
+            --this.contacts;
+
+            if (this.contacts < 0) {
+                this.contacts = 0;
+            }
         }
     };
 
@@ -2005,7 +2043,7 @@
      * @private
      * @inner
      */
-    function abortTouchContacts( tracker, event, pointsList ) {
+    function abortContacts( tracker, event, pointsList ) {
         var i,
             gPointCount = pointsList.getLength(),
             abortGPoints = [];
@@ -2015,12 +2053,12 @@
         }
 
         if ( abortGPoints.length > 0 ) {
-            // simulate touchend
+            // simulate touchend/mouseup
             updatePointersUp( tracker, event, abortGPoints, 0 ); // 0 means primary button press/release or touch contact
             // release pointer capture
             pointsList.captureCount = 1;
-            releasePointer( tracker, 'touch' );
+            releasePointer( tracker, pointsList.type );
-            // simulate touchleave
+            // simulate touchleave/mouseout
             updatePointersExit( tracker, event, abortGPoints );
         }
     }
@@ -2043,7 +2081,7 @@
 
         if ( pointsList.getLength() > event.touches.length - touchCount ) {
             $.console.warn('Tracked touch contact count doesn\'t match event.touches.length. Removing all tracked touch pointers.');
-            abortTouchContacts( tracker, event, pointsList );
+            abortContacts( tracker, event, pointsList );
         }
 
         for ( i = 0; i < touchCount; i++ ) {
@@ -2213,7 +2251,7 @@
     function onTouchCancel( tracker, event ) {
         var pointsList = tracker.getActivePointersListByType('touch');
 
-        abortTouchContacts( tracker, event, pointsList );
+        abortContacts( tracker, event, pointsList );
     }
 
 
@@ -2690,6 +2728,14 @@
             }
         }
 
+        // Some pointers may steal control from another pointer without firing the appropriate release events
+        // e.g. Touching a screen while click-dragging with certain mice.
+        var otherPointsLists = tracker.getActivePointersListExceptType(gPoints[ 0 ].type);
+        for (i = 0; i < otherPointsLists.length; i++) {
+            //If another pointer has contact, simulate the release
+            abortContacts(tracker, event, otherPointsLists[i]); // No-op if no active pointer
+        }
+
         // Only capture and track primary button, pen, and touch contacts
         if ( buttonChanged !== 0 ) {
             // Aux Press
@@ -2740,7 +2786,7 @@
                 startTrackingPointer( pointsList, curGPoint );
             }
 
-            pointsList.contacts++;
+            pointsList.addContact();
             //$.console.log('contacts++ ', pointsList.contacts);
 
             if ( tracker.dragHandler || tracker.dragEndHandler || tracker.pinchHandler ) {
@@ -2880,11 +2926,10 @@
             }
 
             // A primary mouse button may have been released while the non-primary button was down
-            if (pointsList.contacts > 0 && pointsList.type === 'mouse') {
+            var otherPointsList = tracker.getActivePointersListByType("mouse");
-                // Stop tracking the mouse; see https://github.com/openseadragon/openseadragon/pull/1223
+            // Stop tracking the mouse; see https://github.com/openseadragon/openseadragon/pull/1223
-                pointsList.contacts--;
+            abortContacts(tracker, event, otherPointsList); // No-op if no active pointer
-                return true;
+
-            }
             return false;
         }
 
@@ -2913,7 +2958,7 @@
                 if ( wasCaptured ) {
                     // Pointer was activated in our element but could have been removed in any element since events are captured to our element
 
-                    pointsList.contacts--;
+                    pointsList.removeContact();
                     //$.console.log('contacts-- ', pointsList.contacts);
 
                     if ( tracker.dragHandler || tracker.dragEndHandler || tracker.pinchHandler ) {