Implement SkXfermode image filter

gm/arithmode.cpp

Index: gm/arithmode.cpp
diff --git a/gm/arithmode.cpp b/gm/arithmode.cpp
index 63be6c387166660f22c03bcc98c3baad3ecac90a..715103273271fd0c0542cbf0399539056f7376f0 100644
--- a/gm/arithmode.cpp
+++ b/gm/arithmode.cpp
@@ -11,7 +11,9 @@
 #include "SkShader.h"
 
 #include "SkArithmeticMode.h"
+#include "SkBitmapSource.h"
 #include "SkGradientShader.h"
+#include "SkXfermodeImageFilter.h"
 #define WW  100
 #define HH  32
 
@@ -113,7 +115,15 @@ protected:
             canvas->drawBitmap(dst, x, y, NULL);
             SkXfermode* xfer = SkArithmeticMode::Create(k[0], k[1], k[2], k[3]);
             SkPaint paint;
-            paint.setXfermode(xfer)->unref();
+            if ((k - K) % 2 != 0) {
+                // Test out an arithmode filter created as an xfermode image filter
+                SkAutoTUnref<SkImageFilter> background(new SkBitmapSource(dst));
+                SkXfermode* xfer = SkArithmeticMode::Create(0, one, one, 0);

[reed1, 2013/05/30 20:42:44]

I think this xfer leaks, and it makes us leak the outer-xfer as well.

[Stephen White, 2013/05/30 20:50:26]

Good point. This whole whole section never gets exercised, actually, since k - K
modulus 2 is always zero. Doh! So much for being clever.

I'm going to add a new case to the xfermodeimagefilter GM instead, which has no
baselines yet so it won't turn the bots red.

+                SkAutoTUnref<SkImageFilter> filter(new SkXfermodeImageFilter(xfer, background));
+                paint.setImageFilter(filter);
+            } else {
+                paint.setXfermode(xfer)->unref();
+            }
             canvas->drawBitmap(src, x, y, &paint);
             canvas->restore();
             x += gap;