diff --git a/dist/maptalks.markercluster.js b/dist/maptalks.markercluster.js
index 3ee860b..42a8d49 100644
--- a/dist/maptalks.markercluster.js
+++ b/dist/maptalks.markercluster.js
@@ -126,7 +126,9 @@ ClusterLayer.registerJSONType('ClusterLayer');
 
 var defaultTextSymbol = {
     'textFaceName': '"microsoft yahei"',
-    'textSize': 16
+    'textSize': 16,
+    'textDx': 0,
+    'textDy': 0
 };
 
 var defaultSymbol = {
@@ -155,11 +157,16 @@ ClusterLayer.registerRenderer('canvas', function (_maptalks$renderer$Ve) {
     }
 
     _class.prototype.checkResources = function checkResources() {
+        var symbol = this.layer.options['symbol'] || defaultSymbol;
+        if (symbol === this._symbolResourceChecked) {
+            return [];
+        }
         var resources = _maptalks$renderer$Ve.prototype.checkResources.apply(this, arguments);
-        var res = maptalks.Util.getExternalResources(this.layer.options['symbol'] || defaultSymbol, true);
+        var res = maptalks.Util.getExternalResources(symbol, true);
         if (res) {
             resources.push.apply(resources, res);
         }
+        this._symbolResourceChecked = symbol;
         return resources;
     };
 
@@ -203,7 +210,7 @@ ClusterLayer.registerRenderer('canvas', function (_maptalks$renderer$Ve) {
             width = sprite.canvas.width;
             height = sprite.canvas.height;
             pt = map._prjToContainerPoint(zoomClusters[p]['center']);
-            pExt = new maptalks.PointExtent(pt.substract(width, height), pt.add(width, height));
+            pExt = new maptalks.PointExtent(pt.subs(width, height), pt.add(width, height));
             if (!extent.intersects(pExt)) {
                 continue;
             }
@@ -237,17 +244,17 @@ ClusterLayer.registerRenderer('canvas', function (_maptalks$renderer$Ve) {
 
     _class.prototype.onGeometryAdd = function onGeometryAdd() {
         this._clusterNeedRedraw = true;
-        this.render();
+        _maptalks$renderer$Ve.prototype.onGeometryAdd.apply(this, arguments);
     };
 
     _class.prototype.onGeometryRemove = function onGeometryRemove() {
         this._clusterNeedRedraw = true;
-        this.render();
+        _maptalks$renderer$Ve.prototype.onGeometryRemove.apply(this, arguments);
     };
 
     _class.prototype.onGeometryPositionChange = function onGeometryPositionChange() {
         this._clusterNeedRedraw = true;
-        this.render();
+        _maptalks$renderer$Ve.prototype.onGeometryPositionChange.apply(this, arguments);
     };
 
     _class.prototype.onRemove = function onRemove() {
@@ -318,11 +325,11 @@ ClusterLayer.registerRenderer('canvas', function (_maptalks$renderer$Ve) {
                     _this4.completeRender();
                 } else {
                     _this4._drawClusters(clusters, frame.styles.d);
-                    _this4.requestMapToRender();
+                    _this4.setCanvasUpdated();
                 }
             }).play();
             this._drawClusters(clusters, 0);
-            this.requestMapToRender();
+            this.setCanvasUpdated();
         } else {
             this._animated = false;
             this._drawClusters(clusters, 1);
@@ -364,7 +371,7 @@ ClusterLayer.registerRenderer('canvas', function (_maptalks$renderer$Ve) {
             var pt = map._prjToContainerPoint(c['center']);
             if (c.parent) {
                 var parent = map._prjToContainerPoint(c.parent['center']);
-                pt = parent.add(pt.substract(parent)._multi(ratio));
+                pt = parent.add(pt.sub(parent)._multi(ratio));
             }
             if (matrix) {
                 pt = matrix.applyToPointInstance(pt);
@@ -383,13 +390,15 @@ ClusterLayer.registerRenderer('canvas', function (_maptalks$renderer$Ve) {
         }
         ctx.globalAlpha = opacity * op;
         if (sprite) {
-            var pos = pt.add(sprite.offset)._substract(sprite.canvas.width / 2, sprite.canvas.height / 2);
+            var pos = pt.add(sprite.offset)._subs(sprite.canvas.width / 2, sprite.canvas.height / 2);
             ctx.drawImage(sprite.canvas, pos.x, pos.y);
         }
 
         if (this.layer.options['drawClusterText'] && grid['textSize']) {
             maptalks.Canvas.prepareCanvasFont(ctx, this._textSymbol);
-            maptalks.Canvas.fillText(ctx, grid['count'], pt.substract(grid['textSize']));
+            var dx = this._textSymbol['textDx'] || 0;
+            var dy = this._textSymbol['textDy'] || 0;
+            maptalks.Canvas.fillText(ctx, grid['count'], pt.sub(grid['textSize']).add(dx, dy));
         }
         ctx.globalAlpha = opacity;
     };
diff --git a/dist/maptalks.markercluster.min.js b/dist/maptalks.markercluster.min.js
index 2b66c12..05a0b8d 100644
--- a/dist/maptalks.markercluster.min.js
+++ b/dist/maptalks.markercluster.min.js
@@ -6,4 +6,4 @@
 /*!
  * requires maptalks@^0.23.0 
  */
-!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?e(exports,require("maptalks")):"function"==typeof define&&define.amd?define(["exports","maptalks"],e):e(t.maptalks=t.maptalks||{},t.maptalks)}(this,function(t,e){"use strict";function r(t,e){for(var r=Object.getOwnPropertyNames(e),o=0;o<r.length;o++){var i=r[o],n=Object.getOwnPropertyDescriptor(e,i);n&&n.configurable&&void 0===t[i]&&Object.defineProperty(t,i,n)}return t}function o(t,e){if(!(t instanceof e))throw new TypeError("Cannot call a class as a function")}function i(t,e){if(!t)throw new ReferenceError("this hasn't been initialised - super() hasn't been called");return!e||"object"!=typeof e&&"function"!=typeof e?t:e}function n(t,e){if("function"!=typeof e&&null!==e)throw new TypeError("Super expression must either be null or a function, not "+typeof e);t.prototype=Object.create(e&&e.prototype,{constructor:{value:t,enumerable:!1,writable:!0,configurable:!0}}),e&&(Object.setPrototypeOf?Object.setPrototypeOf(t,e):r(t,e))}var s={maxClusterRadius:160,geometryEvents:!1,symbol:null,drawClusterText:!0,textSymbol:null,animation:!0,animationDuration:450,maxClusterZoom:null},a=function(t){function r(){return o(this,r),i(this,t.apply(this,arguments))}return n(r,t),r.fromJSON=function(t){if(!t||"ClusterLayer"!==t.type)return null;for(var o=new r(t.id,t.options),i=t.geometries,n=[],s=0;s<i.length;s++){var a=e.Geometry.fromJSON(i[s]);a&&n.push(a)}return o.addGeometry(n),o},r.prototype.addMarker=function(t){return this.addGeometry(t)},r.prototype.addGeometry=function(r){for(var o=0,i=r.length;o<=i;o++)if(!r[o]instanceof e.Marker)throw new Error("Only a point(Marker) can be added into a ClusterLayer");return t.prototype.addGeometry.apply(this,arguments)},r.prototype.onConfig=function(e){if(t.prototype.onConfig.call(this,e),e.maxClusterRadius||e.symbol||e.drawClusterText||e.textSymbol||e.maxClusterZoom){var r=this._getRenderer();r&&r.render()}return this},r.prototype.identify=function(t,e){return this._getRenderer()?this._getRenderer().identify(t,e):null},r.prototype.toJSON=function(){var e=t.prototype.toJSON.call(this);return e.type="ClusterLayer",e},r}(e.VectorLayer);a.mergeOptions(s),a.registerJSONType("ClusterLayer");var u={textFaceName:'"microsoft yahei"',textSize:16},l={markerType:"ellipse",markerFill:{property:"count",type:"interval",stops:[[0,"rgb(135, 196, 240)"],[9,"#1bbc9b"],[99,"rgb(216, 115, 149)"]]},markerFillOpacity:.7,markerLineOpacity:1,markerLineWidth:3,markerLineColor:"#fff",markerWidth:{property:"count",type:"interval",stops:[[0,40],[9,60],[99,80]]},markerHeight:{property:"count",type:"interval",stops:[[0,40],[9,60],[99,80]]}};a.registerRenderer("canvas",function(t){function r(e){o(this,r);var n=i(this,t.call(this,e));return n._animated=!0,n._refreshStyle(),n._clusterNeedRedraw=!0,n}return n(r,t),r.prototype.checkResources=function(){var r=t.prototype.checkResources.apply(this,arguments),o=e.Util.getExternalResources(this.layer.options.symbol||l,!0);return o&&r.push.apply(r,o),r},r.prototype.draw=function(){this.canvas||this.prepareCanvas();var r=this.getMap(),o=r.getZoom(),i=this.layer.options.maxClusterZoom;if(i&&o>i)return delete this._currentClusters,this._markersToDraw=this.layer._geoList,void t.prototype.draw.apply(this,arguments);this._clusterNeedRedraw&&(this._clearDataCache(),this._computeGrid(),this._clusterNeedRedraw=!1);var n=this._clusterCache[o]?this._clusterCache[o].clusters:null;this._markersToDraw=[];var s=r.getContainerExtent(),a=[],u=void 0,l=void 0,c=void 0,p=void 0,h=void 0,y=void 0;for(var d in n)if(this._currentGrid=n[d],1!==n[d].count)c=this._getSprite(),p=c.canvas.width,h=c.canvas.height,u=r._prjToContainerPoint(n[d].center),l=new e.PointExtent(u.substract(p,h),u.add(p,h)),s.intersects(l)&&(y=e.StringUtil.getFont(this._textSymbol),n[d].textSize||(n[d].textSize=e.StringUtil.stringLength(n[d].count,y).toPoint()._multi(.5)),a.push(n[d]));else{var _=n[d].children[0];_._cluster=n[d],this._markersToDraw.push(_)}this._drawLayer(a)},r.prototype.forEachGeo=function(t,e){this._markersToDraw&&this._markersToDraw.forEach(function(r){e?t.call(e,r):t(r)})},r.prototype.drawOnInteracting=function(){this._currentClusters&&this._drawClusters(this._currentClusters,1),t.prototype.drawOnInteracting.apply(this,arguments)},r.prototype.onGeometryAdd=function(){this._clusterNeedRedraw=!0,this.render()},r.prototype.onGeometryRemove=function(){this._clusterNeedRedraw=!0,this.render()},r.prototype.onGeometryPositionChange=function(){this._clusterNeedRedraw=!0,this.render()},r.prototype.onRemove=function(){this._clearDataCache()},r.prototype.transform=function(t){return this._currentClusters&&this._drawClusters(this._currentClusters,1,t),!0},r.prototype.identify=function(t){var e=this.getMap();if(t=e.coordinateToContainerPoint(t),!this._currentClusters)return null;for(var r=this._currentGrid,o=0;o<this._currentClusters.length;o++){var i=this._currentClusters[o],n=e._prjToContainerPoint(i.center);this._currentGrid=i;var s=this._getSprite().canvas.width;if(t.distanceTo(n)<=s)return{center:e.getProjection().unproject(i.center.copy()),children:i.children.slice(0)}}return this._currentGrid=r,null},r.prototype.onSymbolChanged=function(){this._refreshStyle(),this._computeGrid(),this._stopAnim(),this.draw()},r.prototype._refreshStyle=function(){var t=this,r=this.layer.options.symbol||l,o=this.layer.options.textSymbol||u,i=function(){return[t.getMap().getZoom(),t._currentGrid]};this._symbol=e.MapboxUtil.loadFunctionTypes(r,i),this._textSymbol=e.MapboxUtil.loadFunctionTypes(o,i)},r.prototype._drawLayer=function(t){var r=this;this._currentClusters=t,delete this._clusterMaskExtent;var o=this.layer;o.options.animation&&this._animated&&"out"===this._inout?(this._player=e.animation.Animation.animate({d:[0,1]},{speed:o.options.animationDuration,easing:"inAndOut"},function(e){"finished"===e.state.playState?(r._animated=!1,r._drawMarkers(),r.completeRender()):(r._drawClusters(t,e.styles.d),r.requestMapToRender())}).play(),this._drawClusters(t,0),this.requestMapToRender()):(this._animated=!1,this._drawClusters(t,1),this._drawMarkers(),this.completeRender())},r.prototype._drawMarkers=function(){t.prototype.drawGeos.call(this,this._clusterMaskExtent)},r.prototype._drawClusters=function(t,e,r){var o=this;r=r?r.container:null,this._clusterMaskExtent=this.prepareCanvas();var i=this.getMap(),n={};this.layer.options.animation&&e<1&&t.forEach(function(t){if(t.parent){var s=i._prjToContainerPoint(t.parent.center);n[t.parent.key]||(r&&(s=r.applyToPointInstance(s)),n[t.parent.key]=1,o._drawCluster(s,t.parent,1-e))}}),0!==e&&t.forEach(function(t){var n=i._prjToContainerPoint(t.center);if(t.parent){var s=i._prjToContainerPoint(t.parent.center);n=s.add(n.substract(s)._multi(e))}r&&(n=r.applyToPointInstance(n)),o._drawCluster(n,t,e>.5?1:e)})},r.prototype._drawCluster=function(t,r,o){this._currentGrid=r;var i=this.context,n=this._getSprite(),s=i.globalAlpha;if(s*o!==0){if(i.globalAlpha=s*o,n){var a=t.add(n.offset)._substract(n.canvas.width/2,n.canvas.height/2);i.drawImage(n.canvas,a.x,a.y)}this.layer.options.drawClusterText&&r.textSize&&(e.Canvas.prepareCanvasFont(i,this._textSymbol),e.Canvas.fillText(i,r.count,t.substract(r.textSize))),i.globalAlpha=s}},r.prototype._getSprite=function(){this._spriteCache||(this._spriteCache={});var t=e.Util.getSymbolStamp(this._symbol);return this._spriteCache[t]||(this._spriteCache[t]=new e.Marker([0,0],{symbol:this._symbol})._getSprite(this.resources,this.getMap().CanvasClass)),this._spriteCache[t]},r.prototype._initGridSystem=function(){var t=[],e=void 0,r=void 0;this.layer.forEach(function(o){r=o._getPrjCoordinates(),e=e?e._combine(o._getPrjExtent()):o._getPrjExtent(),t.push({x:r.x,y:r.y,id:o._getInternalId(),geometry:o})}),this._markerExtent=e,this._markerPoints=t},r.prototype._computeGrid=function(){var t=this.getMap(),e=t.getZoom();this._markerExtent||this._initGridSystem(),this._clusterCache||(this._clusterCache={});var r=t._getResolution(t.getMinZoom())>t._getResolution(t.getMaxZoom())?e-1:e+1;this._clusterCache[r]&&this._clusterCache[r].length===this.layer.getCount()&&(this._clusterCache[e]=this._clusterCache[r]),this._clusterCache[e]||(this._clusterCache[e]=this._computeZoomGrid(e))},r.prototype._computeZoomGrid=function(t){if(!this._markerExtent)return null;var r=this.getMap(),o=r._getResolution(t)*this.layer.options.maxClusterRadius,i=r._getResolution(t-1)?r._getResolution(t-1)*this.layer.options.maxClusterRadius:null,n=this._clusterCache[t-1];!n&&t-1>=r.getMinZoom()&&(this._clusterCache[t-1]=n=this._computeZoomGrid(t-1));for(var s=this._markerPoints,a={},u=this._markerExtent.getMin(),l=void 0,c=void 0,p=void 0,h=void 0,y=void 0,d=void 0,_=0,m=s.length;_<m;_++)l=Math.floor((s[_].x-u.x)/o),c=Math.floor((s[_].y-u.y)/o),p=l+"_"+c,a[p]?(a[p].sum._add(new e.Coordinate(s[_].x,s[_].y)),a[p].count++,a[p].center=a[p].sum.multi(1/a[p].count),a[p].children.push(s[_].geometry)):(a[p]={sum:new e.Coordinate(s[_].x,s[_].y),center:new e.Coordinate(s[_].x,s[_].y),count:1,children:[s[_].geometry],key:p+""},i&&n&&(h=Math.floor((s[_].x-u.x)/i),y=Math.floor((s[_].y-u.y)/i),d=h+"_"+y,a[p].parent=n.clusterMap[d]));return this._mergeClusters(a,o/2)},r.prototype._mergeClusters=function(t,e){var r={};for(var o in t)r[o]=t[o];var i={},n={},s=void 0,a=void 0;for(var u in t)if(s=t[u],!n[s.key])for(var l=s.key.split("_"),c=+l[0],p=+l[1],h=-1;h<=1;h++)for(var y=-1;y<=1;y++)if(0!==h||0!==y){var d=c+h+"_"+(p+y);a=t[d],a&&this._distanceTo(s.center,a.center)<=e&&(i[s.key]||(i[s.key]=[]),i[s.key].push(a),n[a.key]=1)}for(var _ in i){var m=t[_];if(m){for(var f=i[_],v=0;v<f.length;v++)t[f[v].key]&&(m.sum._add(f[v].sum),m.count+=f[v].count,m.children.concat(f[v].geometry),r[f[v].key]=m,delete t[f[v].key]);m.center=m.sum.multi(1/m.count)}}return{clusters:t,clusterMap:r}},r.prototype._distanceTo=function(t,e){var r=t.x-e.x,o=t.y-e.y;return Math.sqrt(r*r+o*o)},r.prototype._stopAnim=function(){this._player&&"finished"!==this._player.playState&&this._player.cancel()},r.prototype.onZoomStart=function(e){this._inout=e.from>e.to?"in":"out",this._stopAnim(),t.prototype.onZoomStart.call(this,e)},r.prototype.onZoomEnd=function(){this._animated=!0,this._computeGrid(),t.prototype.onZoomEnd.apply(this,arguments)},r.prototype._clearDataCache=function(){this._stopAnim(),delete this._markerExtent,delete this._markerPoints,delete this._clusterCache},r}(e.renderer.VectorLayerCanvasRenderer)),t.ClusterLayer=a,Object.defineProperty(t,"__esModule",{value:!0}),"undefined"!=typeof console&&console.log("maptalks.markercluster v0.4.1, requires maptalks@^0.23.0.")});
\ No newline at end of file
+!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?e(exports,require("maptalks")):"function"==typeof define&&define.amd?define(["exports","maptalks"],e):e(t.maptalks=t.maptalks||{},t.maptalks)}(this,function(t,e){"use strict";function r(t,e){for(var r=Object.getOwnPropertyNames(e),o=0;o<r.length;o++){var i=r[o],n=Object.getOwnPropertyDescriptor(e,i);n&&n.configurable&&void 0===t[i]&&Object.defineProperty(t,i,n)}return t}function o(t,e){if(!(t instanceof e))throw new TypeError("Cannot call a class as a function")}function i(t,e){if(!t)throw new ReferenceError("this hasn't been initialised - super() hasn't been called");return!e||"object"!=typeof e&&"function"!=typeof e?t:e}function n(t,e){if("function"!=typeof e&&null!==e)throw new TypeError("Super expression must either be null or a function, not "+typeof e);t.prototype=Object.create(e&&e.prototype,{constructor:{value:t,enumerable:!1,writable:!0,configurable:!0}}),e&&(Object.setPrototypeOf?Object.setPrototypeOf(t,e):r(t,e))}var s={maxClusterRadius:160,geometryEvents:!1,symbol:null,drawClusterText:!0,textSymbol:null,animation:!0,animationDuration:450,maxClusterZoom:null},a=function(t){function r(){return o(this,r),i(this,t.apply(this,arguments))}return n(r,t),r.fromJSON=function(t){if(!t||"ClusterLayer"!==t.type)return null;for(var o=new r(t.id,t.options),i=t.geometries,n=[],s=0;s<i.length;s++){var a=e.Geometry.fromJSON(i[s]);a&&n.push(a)}return o.addGeometry(n),o},r.prototype.addMarker=function(t){return this.addGeometry(t)},r.prototype.addGeometry=function(r){for(var o=0,i=r.length;o<=i;o++)if(!r[o]instanceof e.Marker)throw new Error("Only a point(Marker) can be added into a ClusterLayer");return t.prototype.addGeometry.apply(this,arguments)},r.prototype.onConfig=function(e){if(t.prototype.onConfig.call(this,e),e.maxClusterRadius||e.symbol||e.drawClusterText||e.textSymbol||e.maxClusterZoom){var r=this._getRenderer();r&&r.render()}return this},r.prototype.identify=function(t,e){return this._getRenderer()?this._getRenderer().identify(t,e):null},r.prototype.toJSON=function(){var e=t.prototype.toJSON.call(this);return e.type="ClusterLayer",e},r}(e.VectorLayer);a.mergeOptions(s),a.registerJSONType("ClusterLayer");var p={textFaceName:'"microsoft yahei"',textSize:16,textDx:0,textDy:0},l={markerType:"ellipse",markerFill:{property:"count",type:"interval",stops:[[0,"rgb(135, 196, 240)"],[9,"#1bbc9b"],[99,"rgb(216, 115, 149)"]]},markerFillOpacity:.7,markerLineOpacity:1,markerLineWidth:3,markerLineColor:"#fff",markerWidth:{property:"count",type:"interval",stops:[[0,40],[9,60],[99,80]]},markerHeight:{property:"count",type:"interval",stops:[[0,40],[9,60],[99,80]]}};a.registerRenderer("canvas",function(t){function r(e){o(this,r);var n=i(this,t.call(this,e));return n._animated=!0,n._refreshStyle(),n._clusterNeedRedraw=!0,n}return n(r,t),r.prototype.checkResources=function(){var r=this.layer.options.symbol||l;if(r===this._symbolResourceChecked)return[];var o=t.prototype.checkResources.apply(this,arguments),i=e.Util.getExternalResources(r,!0);return i&&o.push.apply(o,i),this._symbolResourceChecked=r,o},r.prototype.draw=function(){this.canvas||this.prepareCanvas();var r=this.getMap(),o=r.getZoom(),i=this.layer.options.maxClusterZoom;if(i&&o>i)return delete this._currentClusters,this._markersToDraw=this.layer._geoList,void t.prototype.draw.apply(this,arguments);this._clusterNeedRedraw&&(this._clearDataCache(),this._computeGrid(),this._clusterNeedRedraw=!1);var n=this._clusterCache[o]?this._clusterCache[o].clusters:null;this._markersToDraw=[];var s=r.getContainerExtent(),a=[],p=void 0,l=void 0,u=void 0,c=void 0,h=void 0,y=void 0;for(var d in n)if(this._currentGrid=n[d],1!==n[d].count)u=this._getSprite(),c=u.canvas.width,h=u.canvas.height,p=r._prjToContainerPoint(n[d].center),l=new e.PointExtent(p.subs(c,h),p.add(c,h)),s.intersects(l)&&(y=e.StringUtil.getFont(this._textSymbol),n[d].textSize||(n[d].textSize=e.StringUtil.stringLength(n[d].count,y).toPoint()._multi(.5)),a.push(n[d]));else{var _=n[d].children[0];_._cluster=n[d],this._markersToDraw.push(_)}this._drawLayer(a)},r.prototype.forEachGeo=function(t,e){this._markersToDraw&&this._markersToDraw.forEach(function(r){e?t.call(e,r):t(r)})},r.prototype.drawOnInteracting=function(){this._currentClusters&&this._drawClusters(this._currentClusters,1),t.prototype.drawOnInteracting.apply(this,arguments)},r.prototype.onGeometryAdd=function(){this._clusterNeedRedraw=!0,t.prototype.onGeometryAdd.apply(this,arguments)},r.prototype.onGeometryRemove=function(){this._clusterNeedRedraw=!0,t.prototype.onGeometryRemove.apply(this,arguments)},r.prototype.onGeometryPositionChange=function(){this._clusterNeedRedraw=!0,t.prototype.onGeometryPositionChange.apply(this,arguments)},r.prototype.onRemove=function(){this._clearDataCache()},r.prototype.transform=function(t){return this._currentClusters&&this._drawClusters(this._currentClusters,1,t),!0},r.prototype.identify=function(t){var e=this.getMap();if(t=e.coordinateToContainerPoint(t),!this._currentClusters)return null;for(var r=this._currentGrid,o=0;o<this._currentClusters.length;o++){var i=this._currentClusters[o],n=e._prjToContainerPoint(i.center);this._currentGrid=i;var s=this._getSprite().canvas.width;if(t.distanceTo(n)<=s)return{center:e.getProjection().unproject(i.center.copy()),children:i.children.slice(0)}}return this._currentGrid=r,null},r.prototype.onSymbolChanged=function(){this._refreshStyle(),this._computeGrid(),this._stopAnim(),this.draw()},r.prototype._refreshStyle=function(){var t=this,r=this.layer.options.symbol||l,o=this.layer.options.textSymbol||p,i=function(){return[t.getMap().getZoom(),t._currentGrid]};this._symbol=e.MapboxUtil.loadFunctionTypes(r,i),this._textSymbol=e.MapboxUtil.loadFunctionTypes(o,i)},r.prototype._drawLayer=function(t){var r=this;this._currentClusters=t,delete this._clusterMaskExtent;var o=this.layer;o.options.animation&&this._animated&&"out"===this._inout?(this._player=e.animation.Animation.animate({d:[0,1]},{speed:o.options.animationDuration,easing:"inAndOut"},function(e){"finished"===e.state.playState?(r._animated=!1,r._drawMarkers(),r.completeRender()):(r._drawClusters(t,e.styles.d),r.setCanvasUpdated())}).play(),this._drawClusters(t,0),this.setCanvasUpdated()):(this._animated=!1,this._drawClusters(t,1),this._drawMarkers(),this.completeRender())},r.prototype._drawMarkers=function(){t.prototype.drawGeos.call(this,this._clusterMaskExtent)},r.prototype._drawClusters=function(t,e,r){var o=this;r=r?r.container:null,this._clusterMaskExtent=this.prepareCanvas();var i=this.getMap(),n={};this.layer.options.animation&&e<1&&t.forEach(function(t){if(t.parent){var s=i._prjToContainerPoint(t.parent.center);n[t.parent.key]||(r&&(s=r.applyToPointInstance(s)),n[t.parent.key]=1,o._drawCluster(s,t.parent,1-e))}}),0!==e&&t.forEach(function(t){var n=i._prjToContainerPoint(t.center);if(t.parent){var s=i._prjToContainerPoint(t.parent.center);n=s.add(n.sub(s)._multi(e))}r&&(n=r.applyToPointInstance(n)),o._drawCluster(n,t,e>.5?1:e)})},r.prototype._drawCluster=function(t,r,o){this._currentGrid=r;var i=this.context,n=this._getSprite(),s=i.globalAlpha;if(s*o!==0){if(i.globalAlpha=s*o,n){var a=t.add(n.offset)._subs(n.canvas.width/2,n.canvas.height/2);i.drawImage(n.canvas,a.x,a.y)}if(this.layer.options.drawClusterText&&r.textSize){e.Canvas.prepareCanvasFont(i,this._textSymbol);var p=this._textSymbol.textDx||0,l=this._textSymbol.textDy||0;e.Canvas.fillText(i,r.count,t.sub(r.textSize).add(p,l))}i.globalAlpha=s}},r.prototype._getSprite=function(){this._spriteCache||(this._spriteCache={});var t=e.Util.getSymbolStamp(this._symbol);return this._spriteCache[t]||(this._spriteCache[t]=new e.Marker([0,0],{symbol:this._symbol})._getSprite(this.resources,this.getMap().CanvasClass)),this._spriteCache[t]},r.prototype._initGridSystem=function(){var t=[],e=void 0,r=void 0;this.layer.forEach(function(o){r=o._getPrjCoordinates(),e=e?e._combine(o._getPrjExtent()):o._getPrjExtent(),t.push({x:r.x,y:r.y,id:o._getInternalId(),geometry:o})}),this._markerExtent=e,this._markerPoints=t},r.prototype._computeGrid=function(){var t=this.getMap(),e=t.getZoom();this._markerExtent||this._initGridSystem(),this._clusterCache||(this._clusterCache={});var r=t._getResolution(t.getMinZoom())>t._getResolution(t.getMaxZoom())?e-1:e+1;this._clusterCache[r]&&this._clusterCache[r].length===this.layer.getCount()&&(this._clusterCache[e]=this._clusterCache[r]),this._clusterCache[e]||(this._clusterCache[e]=this._computeZoomGrid(e))},r.prototype._computeZoomGrid=function(t){if(!this._markerExtent)return null;var r=this.getMap(),o=r._getResolution(t)*this.layer.options.maxClusterRadius,i=r._getResolution(t-1)?r._getResolution(t-1)*this.layer.options.maxClusterRadius:null,n=this._clusterCache[t-1];!n&&t-1>=r.getMinZoom()&&(this._clusterCache[t-1]=n=this._computeZoomGrid(t-1));for(var s=this._markerPoints,a={},p=this._markerExtent.getMin(),l=void 0,u=void 0,c=void 0,h=void 0,y=void 0,d=void 0,_=0,m=s.length;_<m;_++)l=Math.floor((s[_].x-p.x)/o),u=Math.floor((s[_].y-p.y)/o),c=l+"_"+u,a[c]?(a[c].sum._add(new e.Coordinate(s[_].x,s[_].y)),a[c].count++,a[c].center=a[c].sum.multi(1/a[c].count),a[c].children.push(s[_].geometry)):(a[c]={sum:new e.Coordinate(s[_].x,s[_].y),center:new e.Coordinate(s[_].x,s[_].y),count:1,children:[s[_].geometry],key:c+""},i&&n&&(h=Math.floor((s[_].x-p.x)/i),y=Math.floor((s[_].y-p.y)/i),d=h+"_"+y,a[c].parent=n.clusterMap[d]));return this._mergeClusters(a,o/2)},r.prototype._mergeClusters=function(t,e){var r={};for(var o in t)r[o]=t[o];var i={},n={},s=void 0,a=void 0;for(var p in t)if(s=t[p],!n[s.key])for(var l=s.key.split("_"),u=+l[0],c=+l[1],h=-1;h<=1;h++)for(var y=-1;y<=1;y++)if(0!==h||0!==y){var d=u+h+"_"+(c+y);a=t[d],a&&this._distanceTo(s.center,a.center)<=e&&(i[s.key]||(i[s.key]=[]),i[s.key].push(a),n[a.key]=1)}for(var _ in i){var m=t[_];if(m){for(var f=i[_],v=0;v<f.length;v++)t[f[v].key]&&(m.sum._add(f[v].sum),m.count+=f[v].count,m.children.concat(f[v].geometry),r[f[v].key]=m,delete t[f[v].key]);m.center=m.sum.multi(1/m.count)}}return{clusters:t,clusterMap:r}},r.prototype._distanceTo=function(t,e){var r=t.x-e.x,o=t.y-e.y;return Math.sqrt(r*r+o*o)},r.prototype._stopAnim=function(){this._player&&"finished"!==this._player.playState&&this._player.cancel()},r.prototype.onZoomStart=function(e){this._inout=e.from>e.to?"in":"out",this._stopAnim(),t.prototype.onZoomStart.call(this,e)},r.prototype.onZoomEnd=function(){this._animated=!0,this._computeGrid(),t.prototype.onZoomEnd.apply(this,arguments)},r.prototype._clearDataCache=function(){this._stopAnim(),delete this._markerExtent,delete this._markerPoints,delete this._clusterCache},r}(e.renderer.VectorLayerCanvasRenderer)),t.ClusterLayer=a,Object.defineProperty(t,"__esModule",{value:!0}),"undefined"!=typeof console&&console.log("maptalks.markercluster v0.4.1, requires maptalks@^0.23.0.")});
\ No newline at end of file
diff --git a/index.js b/index.js
index 0406b4b..b5b8dca 100644
--- a/index.js
+++ b/index.js
@@ -94,7 +94,9 @@ ClusterLayer.registerJSONType('ClusterLayer');
 
 const defaultTextSymbol = {
     'textFaceName'      : '"microsoft yahei"',
-    'textSize'          : 16
+    'textSize'          : 16,
+    'textDx'            : 0,
+    'textDy'            : 0
 };
 
 const defaultSymbol = {
@@ -118,11 +120,16 @@ ClusterLayer.registerRenderer('canvas', class extends maptalks.renderer.VectorLa
     }
 
     checkResources() {
+        const symbol = this.layer.options['symbol'] || defaultSymbol;
+        if (symbol === this._symbolResourceChecked) {
+            return [];
+        }
         const resources = super.checkResources.apply(this, arguments);
-        const res = maptalks.Util.getExternalResources(this.layer.options['symbol'] || defaultSymbol, true);
+        const res = maptalks.Util.getExternalResources(symbol, true);
         if (res) {
             resources.push.apply(resources, res);
         }
+        this._symbolResourceChecked = symbol;
         return resources;
     }
 
@@ -161,7 +168,7 @@ ClusterLayer.registerRenderer('canvas', class extends maptalks.renderer.VectorLa
             width = sprite.canvas.width;
             height = sprite.canvas.height;
             pt = map._prjToContainerPoint(zoomClusters[p]['center']);
-            pExt = new maptalks.PointExtent(pt.substract(width, height), pt.add(width, height));
+            pExt = new maptalks.PointExtent(pt.subs(width, height), pt.add(width, height));
             if (!extent.intersects(pExt)) {
                 continue;
             }
@@ -195,17 +202,17 @@ ClusterLayer.registerRenderer('canvas', class extends maptalks.renderer.VectorLa
 
     onGeometryAdd() {
         this._clusterNeedRedraw = true;
-        this.render();
+        super.onGeometryAdd.apply(this, arguments);
     }
 
     onGeometryRemove() {
         this._clusterNeedRedraw = true;
-        this.render();
+        super.onGeometryRemove.apply(this, arguments);
     }
 
     onGeometryPositionChange() {
         this._clusterNeedRedraw = true;
-        this.render();
+        super.onGeometryPositionChange.apply(this, arguments);
     }
 
     onRemove() {
@@ -273,13 +280,13 @@ ClusterLayer.registerRenderer('canvas', class extends maptalks.renderer.VectorLa
                         this.completeRender();
                     } else {
                         this._drawClusters(clusters, frame.styles.d);
-                        this.requestMapToRender();
+                        this.setCanvasUpdated();
                     }
                 }
             )
             .play();
             this._drawClusters(clusters, 0);
-            this.requestMapToRender();
+            this.setCanvasUpdated();
         } else {
             this._animated = false;
             this._drawClusters(clusters, 1);
@@ -319,7 +326,7 @@ ClusterLayer.registerRenderer('canvas', class extends maptalks.renderer.VectorLa
             let pt = map._prjToContainerPoint(c['center']);
             if (c.parent) {
                 const parent = map._prjToContainerPoint(c.parent['center']);
-                pt = parent.add(pt.substract(parent)._multi(ratio));
+                pt = parent.add(pt.sub(parent)._multi(ratio));
             }
             if (matrix) {
                 pt = matrix.applyToPointInstance(pt);
@@ -339,13 +346,15 @@ ClusterLayer.registerRenderer('canvas', class extends maptalks.renderer.VectorLa
         }
         ctx.globalAlpha = opacity * op;
         if (sprite) {
-            const pos = pt.add(sprite.offset)._substract(sprite.canvas.width / 2, sprite.canvas.height / 2);
+            const pos = pt.add(sprite.offset)._subs(sprite.canvas.width / 2, sprite.canvas.height / 2);
             ctx.drawImage(sprite.canvas, pos.x, pos.y);
         }
 
         if (this.layer.options['drawClusterText'] && grid['textSize']) {
             maptalks.Canvas.prepareCanvasFont(ctx, this._textSymbol);
-            maptalks.Canvas.fillText(ctx, grid['count'], pt.substract(grid['textSize']));
+            const dx = this._textSymbol['textDx'] || 0;
+            const dy = this._textSymbol['textDy'] || 0;
+            maptalks.Canvas.fillText(ctx, grid['count'], pt.sub(grid['textSize']).add(dx, dy));
         }
         ctx.globalAlpha = opacity;
     }