fix MultiPolygon as mask, close #1215 (#1216)

Author: fuzhenn

src/geometry/Geometry.js

@@ -988,7 +988,7 @@ class Geometry extends JSONAble(Eventable(Handlerable(Class))) {
         if (this._maskPainter) {
             return this._maskPainter;
         }
-        this._maskPainter = this.getGeometries && this.getGeometries() ?  new CollectionPainter(this) : new Painter(this);
+        this._maskPainter = this.getGeometries && this.getGeometries() ?  new CollectionPainter(this, true) : new Painter(this);
         return this._maskPainter;
     }
 

src/renderer/geometry/CollectionPainter.js

@@ -13,16 +13,17 @@ export default class CollectionPainter extends Class {
     /**
      * @param {GeometryCollection} geometry - geometry to paint
      */
-    constructor(geometry) {
+    constructor(geometry, isMask) {
         super();
         this.geometry = geometry;
+        this.isMask = isMask;
     }
 
     _eachPainter(fn) {
         const geometries = this.geometry.getGeometries();
         let painter;
         for (let i = 0, len = geometries.length; i < len; i++) {
-            painter = geometries[i]._getPainter();
+            painter = this.isMask ? geometries[i]._getMaskPainter() : geometries[i]._getPainter();
             if (!painter) {
                 continue;
             }

test/layer/MaskSpec.js

@@ -206,4 +206,20 @@ describe('Spec of Masks', function () {
         });
     });
 
+    it('mask can return extent', function () {
+        var mask = new maptalks.MultiPolygon([
+            new maptalks.Circle(map.getCenter(), 5).getShell(),
+            new maptalks.Circle(map.locate(map.getCenter(), 10, 0), 5).getShell()
+        ]);
+        var tileLayer = new maptalks.TileLayer('tile', {
+            urlTemplate : TILE_IMAGE,
+            renderer:'canvas'
+        });
+        tileLayer.setMask(mask);
+        map.addLayer(tileLayer);
+        var extent = mask._getMaskPainter().get2DExtent();
+        expect(extent.xmin).to.be.ok();
+        expect(extent.ymin).to.be.ok();
+    });
+
 });