google maps api v3 no smooth dragging

Question

I started implementing my software using maps api v3. Unfortunatelly i found out that v3 API has some serious issues which draws me back from bying a bussiness licence.

Answer 1

Same here. What I noticed is that v3 fires a lot of events while panning the map and the browser tends to choke (FF especially). I say this because I also used Bing Maps API and the number of events per second for viewchange (equivalent for center_changed in Google) is much smaller. Also they provide the method addThrottledHandler() with which you can reduce the number of events generated.

From what I can tell, Google Maps seem to fire one center_changed event for each mousemove event and before the map's view is updated. So you get a lot of events generated but none of them are replicated on the screen; browser chokes on map view updates or it might be that the map waits until there are no more changes and only then it updates the view.

Edit: if we prevent some of the mousemove events to reach Google Maps then the browser will not choke on mousemove events plus all the other events that Google Maps generates from this event, like center_changed, and the map will pan smoothly.

To do this we add an event listener to the #map div (we can add it to body tag also). We add the event for the capture phase. When mouse moves on the screen, first the body tag receives the event then our #map div and then Google Maps elements (divs, tiles). This is the capture phase. After that follows the bubble phase in which the event goes back from Google Maps elements to our #map div and then to the body tag. Usually event handlers are registered for the bubbling phase so if we register a handler for the capture phase we can cancel the event and so there will be no bubbling phase for this event. This also means that Google Maps will not receive the event.

You can increase the period and space parameters to kill more events. Killing too many events means that the map will start to jump from one position to the next. Killing too few means that all events will reach Google Maps and the browser will choke on newly generated events from Google Maps and so the map will jump from one position to the next. Some middle ground works best.

Now after all these, Google Maps will not be as smooth as Bing Maps. This is because Bing Maps use inertia: when you move the map violently, the map will start slowly to follow the mouse and then faster and faster. This creates a very smooth pan indeed.

An interesting fact that I've found is that Google Chrome and Opera/Chrommium will generate about one mousemove event per second even if the mouse doesn't move! This code will kill those events too (because distance is zero for those events).

http://jsfiddle.net/uNm57/ (check js console in Firefox; you should see some events that are stopped and then one allowed event)