Update tooltips, support custom handler.

src/CanvasHandler.js

@@ -4,8 +4,8 @@ import point from './util/point';
 import {domFind} from './util/dom';
 import {inherits} from 'vega-util';
 
-export default function CanvasHandler(loader) {
-  Handler.call(this, loader);
+export default function CanvasHandler(loader, tooltip) {
+  Handler.call(this, loader, tooltip);
   this._down = null;
   this._touch = null;
   this._first = true;
@@ -143,8 +143,8 @@ prototype.fire = function(type, evt, touch) {
   // if hyperlinked, handle link first
   if (type === 'click' && a && a.href) {
     this.handleHref(evt, a, a.href);
-  } else if ((type === 'mouseover' || type === 'mouseout') && a && a.tooltip) {
-    this.handleTooltip(evt, a, type === 'mouseover' ? a.tooltip : null);
+  } else if ((type === 'mouseover' || type === 'mouseout')) {
+    this.handleTooltip(evt, a, type === 'mouseover');
   }
 
   // invoke all registered handlers

src/Handler.js

@@ -1,10 +1,15 @@
 import {domCreate} from './util/dom';
 import {loader} from 'vega-loader';
 
-export default function Handler(customLoader) {
+export default function Handler(customLoader, customTooltip) {
   this._active = null;
   this._handlers = {};
   this._loader = customLoader || loader();
+  this._tooltip = customTooltip || defaultTooltip;
+}
+
+function defaultTooltip(handler, event, item, value) {
+  handler.element().setAttribute('title', value || '');
 }
 
 var prototype = Handler.prototype;
@@ -73,6 +78,9 @@ prototype.handleHref = function(event, item, href) {
     .catch(function() { /* do nothing */ });
 };
 
-prototype.handleTooltip = function(event, item, tooltipText) {
-  this._el.setAttribute('title', tooltipText || '');
+prototype.handleTooltip = function(event, item, show) {
+  if (item && item.tooltip != null) {
+    this._tooltip.call(this._obj, this, event, item,
+      show ? item.tooltip : null);
+  }
 };

src/SVGHandler.js

@@ -2,16 +2,14 @@ import Handler from './Handler';
 import {domFind} from './util/dom';
 import {inherits} from 'vega-util';
 
-export default function SVGHandler(loader) {
-  Handler.call(this, loader);
+export default function SVGHandler(loader, tooltip) {
+  Handler.call(this, loader, tooltip);
   var h = this;
   h._hrefHandler = listener(h, function(evt, item) {
     if (item && item.href) h.handleHref(evt, item, item.href);
   });
   h._tooltipHandler = listener(h, function(evt, item) {
-    if (item && item.tooltip) {
-      h.handleTooltip(evt, item, evt.type === 'mouseover' ? item.tooltip : null);
-    }
+    h.handleTooltip(evt, item, evt.type === 'mouseover');
   });
 }