Do not cache group if a child has shadow.

.travis.yml

@@ -4,3 +4,7 @@ node_js:
   - "6"
   - "4"
 script: 'npm run build && npm run test && npm run lint && npm run lint_tests'
+before_install:
+  - sudo apt-get update -qq
+  - sudo apt-get install libc6 -qq
+dist: trusty

package.json

@@ -47,7 +47,7 @@
     "all": "npm run build && npm run test && npm run lint && npm run lint_tests && npm run export_dist_to_site && npm run export_tests_to_site"
   },
   "optionalDependencies": {
-    "canvas-prebuilt": "1.6.x",
+    "canvas-prebuilt": "1.6.5-prerelease.1",
     "jsdom": "9.x.x",
     "xmldom": "0.1.x"
   },

src/mixins/itext_key_behavior.mixin.js

@@ -173,7 +173,6 @@ fabric.util.object.extend(fabric.IText.prototype, /** @lends fabric.IText.protot
       }
     }
     if (insertedText.length) {
-      console.log(insertedText, fromPaste, fabric.copiedText, fabric.copiedTextStyle)
       if (fromPaste && insertedText.join('') === fabric.copiedText) {
         this.insertNewStyleBlock(insertedText, this.selectionStart, fabric.copiedTextStyle);
       }

src/shapes/group.class.js

@@ -294,6 +294,52 @@
       this._transformDone = false;
     },
 
+    /**
+     * Decide if the object should cache or not.
+     * objectCaching is a global flag, wins over everything
+     * needsItsOwnCache should be used when the object drawing method requires
+     * a cache step. None of the fabric classes requires it.
+     * Generally you do not cache objects in groups because the group outside is cached.
+     * @return {Boolean}
+     */
+    shouldCache: function() {
+      var parentCache = this.objectCaching && (!this.group || this.needsItsOwnCache || !this.group.isCaching());
+      this.caching = parentCache;
+      if (parentCache) {
+        for (var i = 0, len = this._objects.length; i < len; i++) {
+          if (this._objects[i].willDrawShadow()) {
+            this.caching = false;
+            return false;
+          }
+        }
+      }
+      return parentCache;
+    },
+
+    /**
+     * Check if this object or a child object will cast a shadow
+     * @return {Boolean}
+     */
+    willDrawShadow: function() {
+      if (this.shadow) {
+        return true;
+      }
+      for (var i = 0, len = this._objects.length; i < len; i++) {
+        if (this._objects[i].willDrawShadow()) {
+          return true;
+        }
+      }
+      return false;
+    },
+
+    /**
+     * Check if this group or its parent group are caching, recursively up
+     * @return {Boolean}
+     */
+    isCaching: function() {
+      return this.caching || this.group && this.group.isCaching();
+    },
+
     /**
      * Execute the drawing operation for an object on a specified context
      * @param {CanvasRenderingContext2D} ctx Context to render on

src/shapes/object.class.js

@@ -1154,7 +1154,7 @@
         ctx.transform.apply(ctx, this.transformMatrix);
       }
       this.clipTo && fabric.util.clipContext(this, ctx);
-      if (this.objectCaching && (!this.group || this.needsItsOwnCache)) {
+      if (this.shouldCache()) {
         if (!this._cacheCanvas) {
           this._createCacheCanvas();
         }
@@ -1175,6 +1175,28 @@
       ctx.restore();
     },
 
+    /**
+     * Decide if the object should cache or not.
+     * objectCaching is a global flag, wins over everything
+     * needsItsOwnCache should be used when the object drawing method requires
+     * a cache step. None of the fabric classes requires it.
+     * Generally you do not cache objects in groups because the group outside is cached.
+     * @return {Boolean}
+     */
+    shouldCache: function() {
+      return this.objectCaching &&
+      (!this.group || this.needsItsOwnCache || !this.group.isCaching());
+    },
+
+    /**
+     * Check if this object or a child object will cast a shadow
+     * used by Group.shouldCache to know if child has a shadow recursively
+     * @return {Boolean}
+     */
+    willDrawShadow: function() {
+      return !!this.shadow;
+    },
+
     /**
      * Execute the drawing operation for an object on a specified context
      * @param {CanvasRenderingContext2D} ctx Context to render on

src/util/lang_class.js

@@ -61,6 +61,7 @@
         parentMethod = superClassMethod;
         break;
       }
+      // eslint-disable-next-line
       _this = _this.constructor.superclass.prototype;
     }
 

test/unit/group.js

@@ -600,6 +600,53 @@
 
     equal(dataless.objects[0].paths, 'sourcePath', 'the paths have been changed with the sourcePath');
   });
+
+  test('group willDrawShadow', function() {
+    var rect1 = new fabric.Rect({ top: 1, left: 1, width: 2, height: 2, strokeWidth: 0, fill: 'red', opacity: 1, objectCaching: false}),
+        rect2 = new fabric.Rect({ top: 5, left: 5, width: 2, height: 2, strokeWidth: 0, fill: 'red', opacity: 1, objectCaching: false}),
+        rect3 = new fabric.Rect({ top: 5, left: 5, width: 2, height: 2, strokeWidth: 0, fill: 'red', opacity: 1, objectCaching: false}),
+        rect4 = new fabric.Rect({ top: 5, left: 5, width: 2, height: 2, strokeWidth: 0, fill: 'red', opacity: 1, objectCaching: false}),
+        group = new fabric.Group([rect1, rect2]),
+        group2 = new fabric.Group([rect3, rect4]),
+        group3 = new fabric.Group([group, group2]);
+
+    equal(group3.willDrawShadow(), false, 'group will not cast shadow because objects do not have it');
+    group3.shadow = {};
+    equal(group3.willDrawShadow(), true, 'group will cast shadow because group itself has shadow');
+    delete group3.shadow;
+    group2.shadow =  {};
+    equal(group3.willDrawShadow(), true, 'group will cast shadow because inner group2 has shadow');
+    delete group2.shadow;
+    rect1.shadow = {};
+    equal(group3.willDrawShadow(), true, 'group will cast shadow because inner rect1 has shadow');
+    equal(group.willDrawShadow(), true, 'group will cast shadow because inner rect1 has shadow');
+    equal(group2.willDrawShadow(), false, 'group will not cast shadow because no child has shadow');
+  });
+
+  test('group shouldCache', function() {
+    var rect1 = new fabric.Rect({ top: 1, left: 1, width: 2, height: 2, strokeWidth: 0, fill: 'red', opacity: 1, objectCaching: true}),
+        rect2 = new fabric.Rect({ top: 5, left: 5, width: 2, height: 2, strokeWidth: 0, fill: 'red', opacity: 1, objectCaching: true}),
+        rect3 = new fabric.Rect({ top: 5, left: 5, width: 2, height: 2, strokeWidth: 0, fill: 'red', opacity: 1, objectCaching: true}),
+        rect4 = new fabric.Rect({ top: 5, left: 5, width: 2, height: 2, strokeWidth: 0, fill: 'red', opacity: 1, objectCaching: true}),
+        group = new fabric.Group([rect1, rect2], { objectCaching: true}),
+        group2 = new fabric.Group([rect3, rect4], { objectCaching: true}),
+        group3 = new fabric.Group([group, group2], { objectCaching: true});
+
+    equal(group3.shouldCache(), true, 'group3 will cache because no child has shadow');
+    equal(group2.shouldCache(), false, 'group2 will not cache because is drawing on parent group3 cache');
+    equal(rect3.shouldCache(), false, 'rect3 will not cache because is drawing on parent2 group cache');
+
+    group2.shadow = {};
+    rect1.shadow = {};
+
+    equal(group3.shouldCache(), false, 'group3 will cache because children have shadow');
+    equal(group2.shouldCache(), true, 'group2 will cache because is not drawing on parent group3 cache and no children have shadow');
+    equal(group.shouldCache(), false, 'group will not cache because even if is not drawing on parent group3 cache children have shadow');
+
+    equal(rect1.shouldCache(), true, 'rect1 will cache because none of its parent is caching');
+    equal(rect3.shouldCache(), false, 'rect3 will not cache because group2 is caching');
+
+  });
   // asyncTest('cloning group with image', function() {
   //   var rect = new fabric.Rect({ top: 100, left: 100, width: 30, height: 10 }),
   //       img = new fabric.Image(_createImageElement()),