backport subtarget fix

src/canvas.class.js

@@ -1106,7 +1106,8 @@
           pointer = this.getPointer(e, ignoreZoom),
           activeObject = this._activeObject,
           aObjects = this.getActiveObjects(),
-          activeTarget;
+          activeTarget, activeTargetSubs;
+
       // first check current group (if one exists)
       // active group does not check sub targets like normal groups.
       // if active group just exits.
@@ -1126,11 +1127,14 @@
         }
         else {
           activeTarget = activeObject;
+          activeTargetSubs = this.targets;
+          this.targets = [];
         }
       }
       var target = this._searchPossibleTargets(this._objects, pointer);
       if (e[this.altSelectionKey] && target && activeTarget && target !== activeTarget) {
         target = activeTarget;
+        this.targets = activeTargetSubs;
       }
       return target;
     },

test/unit/canvas.js

@@ -465,6 +465,37 @@
     canvas.remove(group);
   });
 
+  test('findTarget with subTargetCheck on activeObject and preserveObjectStacking true', function() {
+    var rect = makeRect({ left: 0, top: 0 }),
+        rect2 = makeRect({ left: 30, top:  30}), target,
+        group = new fabric.Group([rect, rect2]);
+    canvas.preserveObjectStacking = true;
+    canvas.add(group);
+    canvas.setActiveObject(group);
+    group.subTargetCheck = true;
+    target = canvas.findTarget({
+      clientX: 9, clientY: 9
+    });
+    equal(target, group, 'Should return the group');
+    equal(canvas.targets[0], rect, 'should return the rect');
+
+    target = canvas.findTarget({
+      clientX: 9, clientY: 9
+    });
+
+    target = canvas.findTarget({
+      clientX: 9, clientY: 9
+    });
+
+    target = canvas.findTarget({
+      clientX: 9, clientY: 9
+    });
+
+    equal(canvas.targets.length, 1, 'multiple calls to subtarget should not add more to targets');
+
+    canvas.remove(group);
+  });
+
   test('findTarget with perPixelTargetFind', function() {
     ok(typeof canvas.findTarget == 'function');
     var triangle = makeTriangle({ left: 0, top: 0 }), target;