1 files changed, 50 insertions, 0 deletions
diff --git a/gfx/skia/skia/src/core/SkXfermodeInterpretation.cpp b/gfx/skia/skia/src/core/SkXfermodeInterpretation.cpp
new file mode 100644
index 0000000000..607f4c995d
--- /dev/null
+++ b/gfx/skia/skia/src/core/SkXfermodeInterpretation.cpp
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "src/core/SkXfermodeInterpretation.h"
+
+#include "include/core/SkBlendMode.h"
+#include "include/core/SkPaint.h"
+
+static bool just_solid_color(const SkPaint& p) {
+    return SK_AlphaOPAQUE == p.getAlpha() && !p.getColorFilter() && !p.getShader();
+}
+
+SkXfermodeInterpretation SkInterpretXfermode(const SkPaint& paint, bool dstIsOpaque) {
+    const auto bm = paint.asBlendMode();
+    if (!bm) {
+        return kNormal_SkXfermodeInterpretation;
+    }
+    switch (bm.value()) {
+        case SkBlendMode::kSrcOver:
+            return kSrcOver_SkXfermodeInterpretation;
+        case SkBlendMode::kSrc:
+            if (just_solid_color(paint)) {
+                return kSrcOver_SkXfermodeInterpretation;
+            }
+            return kNormal_SkXfermodeInterpretation;
+        case SkBlendMode::kDst:
+            return kSkipDrawing_SkXfermodeInterpretation;
+        case SkBlendMode::kDstOver:
+            if (dstIsOpaque) {
+                return kSkipDrawing_SkXfermodeInterpretation;
+            }
+            return kNormal_SkXfermodeInterpretation;
+        case SkBlendMode::kSrcIn:
+            if (dstIsOpaque && just_solid_color(paint)) {
+                return kSrcOver_SkXfermodeInterpretation;
+            }
+            return kNormal_SkXfermodeInterpretation;
+        case SkBlendMode::kDstIn:
+            if (just_solid_color(paint)) {
+                return kSkipDrawing_SkXfermodeInterpretation;
+            }
+            return kNormal_SkXfermodeInterpretation;
+        default:
+            return kNormal_SkXfermodeInterpretation;
+    }
+}