diff --git a/index.js b/index.js
index c69393b2..697a3d68 100644
--- a/index.js
+++ b/index.js
@@ -48,7 +48,7 @@ export default class Drawer extends Component {
     elevation: PropTypes.number,
     initializeOpen: PropTypes.bool,
     open: PropTypes.bool,
-    negotiatePan: PropTypes.bool,
+    negotiatePan: PropTypes.oneOfType([PropTypes.bool, PropTypes.func]),
     onClose: PropTypes.func,
     onCloseStart: PropTypes.func,
     onOpen: PropTypes.func,
@@ -260,12 +260,18 @@ export default class Drawer extends Component {
   };
 
   onMoveShouldSetPanResponderCapture = (e, gestureState) => {
-    if (this.shouldCaptureGestures() && this.props.negotiatePan) return this.processMoveShouldSet(e, gestureState)
+    if (this.shouldCaptureGestures() && this.negotiatePan(e, gestureState)) {
+      return this.processMoveShouldSet(e, gestureState)
+    }
+
     return false
   };
 
   onMoveShouldSetPanResponder = (e, gestureState) => {
-    if (!this.shouldCaptureGestures() && this.props.negotiatePan) return this.processMoveShouldSet(e, gestureState)
+    if (!this.shouldCaptureGestures() && this.negotiatePan(e, gestureState)) {
+      return this.processMoveShouldSet(e, gestureState)
+    }
+
     return false
   };
 
@@ -307,7 +313,7 @@ export default class Drawer extends Component {
     if (!this._open && Math.abs(gestureState.dy) >= Math.abs(gestureState.dx)) return false
     this._panStartTime = Date.now()
     if (inMask && this.shouldCaptureGestures()) return true
-    if (this.props.negotiatePan) return false
+    if (this.negotiatePan(e, gestureState)) return false
     if (!this.props.acceptPan) return false
     this.terminateActiveTween()
     return true
@@ -318,7 +324,7 @@ export default class Drawer extends Component {
     if (!inMask && (!this.props.acceptPanOnDrawer || this._open === false )) return false
     if (!this.props.acceptPan) return false
 
-    if (!this.props.negotiatePan || this.props.disabled || !this.props.acceptPan || this._panning) return false
+    if (!this.negotiatePan(e, gestureState) || this.props.disabled || !this.props.acceptPan || this._panning) return false
     let delta = this.getGestureDelta(gestureState)
     let deltaOppositeAxis = this.getGestureDeltaOppositeAxis(gestureState)
     let swipeToLeftOrTop = (delta < 0) ? true : false
@@ -358,6 +364,12 @@ export default class Drawer extends Component {
     return false
   }
 
+  negotiatePan = (e, gestureState) => {
+    return typeof this.props.negotiatePan === 'function'
+      ? this.props.negotiatePan(e, gestureState)
+      : this.props.negotiatePan
+  }
+
   testPanResponderMask = (e, gestureState) => {
     if (this.props.disabled) return false
 
@@ -621,3 +633,4 @@ const styles = StyleSheet.create({
     backgroundColor: 'transparent'
   }
 })
+
diff --git a/tweener.js b/tweener.js
index 85bb2688..68393470 100644
--- a/tweener.js
+++ b/tweener.js
@@ -27,7 +27,7 @@ Tween.prototype._rafLoop = function() {
 	}
 
 	var tweenVal = easingTypes[easingType](elapsed, start, end, duration);
-	this._config.onFrame(tweenVal);
+	this._config.onFrame(Math.round(tweenVal));
 
 	requestAnimationFrame(this._rafLoop);
 };