hooked opacity rendering into the buffer canvas logic used for shadows so that strokes and fill opacities aren't applied separately

src/Shape.js

@@ -215,10 +215,12 @@
                 context = canvas.getContext(),
                 drawFunc = this.getDrawFunc(),
                 applyShadow = this.hasShadow() && this.getShadowEnabled(),
+                applyOpacity = this.getOpacity() !== 1,
                 stage, bufferCanvas, bufferContext;
 
             if(drawFunc && this.isVisible()) {
-                if (applyShadow) {
+                // buffer canvas is needed to apply shadows or opacity
+                if (applyShadow || applyOpacity) {
                     stage = this.getStage();
                     bufferCanvas = stage.bufferCanvas;
                     bufferContext = bufferCanvas.getContext();
@@ -230,14 +232,21 @@
                     bufferContext.restore();
 
                     context.save();
+                    if (applyShadow) {
                         context.save();
                         context._applyShadow(this);
                         context.drawImage(bufferCanvas._canvas, 0, 0); 
                         context.restore();
+                    }
+
+                    if (applyOpacity) {
                         context._applyOpacity(this);
+                    }
+
                     context.drawImage(bufferCanvas._canvas, 0, 0);
                     context.restore();
                 }
+                // if buffer canvas is not needed
                 else {
                     context.save();
                         context._applyOpacity(this);

test/unit/Node-test.js

@@ -1911,12 +1911,22 @@ suite('Node', function() {
             radius: 70,
             fill: 'green',
             stroke: 'black',
-            strokeWidth: 4
+            strokeWidth: 20,
+            draggable: true
         });
 
         circle.setOpacity(0.5);
         layer.add(circle);
         stage.add(layer);
+
+        var sceneTrace = layer.getContext().getTrace();
+        //console.log(sceneTrace);
+
+        var bufferTrace = stage.bufferCanvas.getContext().getTrace();
+        //console.log(bufferTrace);
+
+        assert.equal(sceneTrace, 'clearRect(0,0,578,200);save();globalAlpha=0.5;drawImage([object HTMLCanvasElement],0,0);restore();');
+        assert.equal(bufferTrace, 'clearRect(0,0,578,200);save();transform(1,0,0,1,289,100);beginPath();arc(0,0,70,0,6.283,false);closePath();fillStyle=green;fill();lineWidth=20;strokeStyle=black;stroke();restore();');
     });
 
     // ======================================================