Work in progress for being able to control when we cancel events.

src/mousetracker.js

@@ -1963,7 +1963,7 @@
             currentTime: $.now()
         };
 
-        if ( updatePointersDown( tracker, event, [ gPoint ], getStandardizedButton( event.button ) ) ) {
+        if ( updatePointersDown( tracker, event, [ gPoint ], getStandardizedButton( event.button ) ).capture ) {
             $.stopEvent( event );
             capturePointer( tracker, 'mouse' );
         }
@@ -2139,13 +2139,16 @@
             }
         }
 
-        if ( updatePointersDown( tracker, event, gPoints, 0 ) ) { // 0 means primary button press/release or touch contact
+        var result = updatePointersDown( tracker, event, gPoints, 0 ); // 0 means primary button press/release or touch contact
+        if ( result.capture && result.cancel ) {
             $.stopEvent( event );
             capturePointer( tracker, 'touch', touchCount );
         }
 
+        if (result.cancel) {
             $.cancelEvent( event );
         }
+    }
 
 
     /**
@@ -2263,10 +2266,12 @@
             } );
         }
 
-        updatePointersMove( tracker, event, gPoints );
+        var result = updatePointersMove( tracker, event, gPoints );
 
+        if (result.cancel) {
             $.cancelEvent( event );
         }
+    }
 
 
     /**
@@ -2363,7 +2368,7 @@
             currentTime: $.now()
         };
 
-        if ( updatePointersDown( tracker, event, [ gPoint ], event.button ) ) {
+        if ( updatePointersDown( tracker, event, [ gPoint ], event.button ).capture ) {
             $.stopEvent( event );
             capturePointer( tracker, gPoint.type );
         }
@@ -2696,7 +2701,8 @@
      *      Note on chorded button presses (a button pressed when another button is already pressed): In the W3C Pointer Events model,
      *      only one pointerdown/pointerup event combo is fired. Chorded button state changes instead fire pointermove events.
      *
-     * @returns {Boolean} True if pointers should be captured to the tracked element, otherwise false.
+     * @returns {Object} Properties: capture: True if pointers should be captured to the tracked element, otherwise false.
+     * TODO: Document cancel
      */
     function updatePointersDown( tracker, event, gPoints, buttonChanged ) {
         var delegate = THIS[ tracker.hash ],
@@ -2707,6 +2713,11 @@
             curGPoint,
             updateGPoint;
 
+        var output = {
+            capture: false,
+            cancel: true
+        };
+
         if ( typeof event.buttons !== 'undefined' ) {
             pointsList.buttons = event.buttons;
         } else {
@@ -2783,7 +2794,7 @@
                 }
             }
 
-            return false;
+            return output;
         }
 
         for ( i = 0; i < gPointCount; i++ ) {
@@ -2821,8 +2832,7 @@
             if ( pointsList.contacts === 1 ) {
                 // Press
                 if ( tracker.pressHandler ) {
-                    propagate = tracker.pressHandler(
+                    var outgoingEvent = {
-                        {
                         eventSource:          tracker,
                         pointerType:          curGPoint.type,
                         position:             getPointRelativeToAbsolute( curGPoint.contactPos, tracker.element ),
@@ -2831,11 +2841,16 @@
                         originalEvent:        event,
                         preventDefaultAction: false,
                         userData:             tracker.userData
-                        }
+                    };
-                    );
+
+                    propagate = tracker.pressHandler(outgoingEvent);
                     if ( propagate === false ) {
                         $.cancelEvent( event );
                     }
+
+                    if (outgoingEvent.preventDefaultAction) {
+                        output.cancel = false;
+                    }
                 }
             } else if ( pointsList.contacts === 2 ) {
                 if ( tracker.pinchHandler && curGPoint.type === 'touch' ) {
@@ -2847,7 +2862,8 @@
             }
         }
 
-        return true;
+        output.capture = true;
+        return output;
     }
 
 
@@ -3156,6 +3172,10 @@
             delta,
             propagate;
 
+        var output = {
+            cancel: true
+        };
+
         if ( typeof event.buttons !== 'undefined' ) {
             pointsList.buttons = event.buttons;
         }
@@ -3234,8 +3254,7 @@
             if ( tracker.dragHandler ) {
                 updateGPoint = pointsList.asArray()[ 0 ];
                 delta = updateGPoint.currentPos.minus( updateGPoint.lastPos );
-                propagate = tracker.dragHandler(
+                var outgoingEvent = {
-                    {
                     eventSource:          tracker,
                     pointerType:          updateGPoint.type,
                     position:             getPointRelativeToAbsolute( updateGPoint.currentPos, tracker.element ),
@@ -3248,11 +3267,14 @@
                     originalEvent:        event,
                     preventDefaultAction: false,
                     userData:             tracker.userData
-                    }
+                };
-                );
+                propagate = tracker.dragHandler(outgoingEvent);
                 if ( propagate === false ) {
                     $.cancelEvent( event );
                 }
+                if (outgoingEvent.preventDefaultAction) {
+                    output.cancel = false;
+                }
             }
         } else if ( pointsList.contacts === 2 ) {
             // Move (2 contacts, use center)
@@ -3304,6 +3326,8 @@
                 }
             }
         }
+
+        return output;
     }
 
 

src/viewer.js

@@ -2790,6 +2790,7 @@ function onCanvasDrag( event ) {
      * @property {?Object} userData - Arbitrary subscriber-defined object.
      */
     this.raiseEvent( 'canvas-drag', canvasDragEventArgs);
+    event.preventDefaultAction = canvasDragEventArgs.preventDefaultAction;
 
     if ( !canvasDragEventArgs.preventDefaultAction && this.viewport ) {
         gestureSettings = this.gestureSettingsByDeviceType( event.pointerType );
@@ -2942,6 +2943,15 @@ function onCanvasExit( event ) {
 }
 
 function onCanvasPress( event ) {
+    var canvasPressEventArgs = {
+        tracker: event.eventSource,
+        pointerType: event.pointerType,
+        position: event.position,
+        insideElementPressed: event.insideElementPressed,
+        insideElementReleased: event.insideElementReleased,
+        originalEvent: event.originalEvent
+    };
+
     /**
      * Raised when the primary mouse button is pressed or touch starts on the {@link OpenSeadragon.Viewer#canvas} element.
      *
@@ -2957,14 +2967,9 @@ function onCanvasPress( event ) {
      * @property {Object} originalEvent - The original DOM event.
      * @property {?Object} userData - Arbitrary subscriber-defined object.
      */
-    this.raiseEvent( 'canvas-press', {
+    this.raiseEvent( 'canvas-press', canvasPressEventArgs);
-        tracker: event.eventSource,
+
-        pointerType: event.pointerType,
+    event.preventDefaultAction = canvasPressEventArgs.preventDefaultAction;
-        position: event.position,
-        insideElementPressed: event.insideElementPressed,
-        insideElementReleased: event.insideElementReleased,
-        originalEvent: event.originalEvent
-    });
 }
 
 function onCanvasRelease( event ) {