Add a private API for writing the clip to the stencil

Add a private API used by Android framework, which writes the clip
into a stencil buffer. This is used by HWUI to clip the WebView.

Bug: 31489986
Change-Id: I94515f1539acd9d069c8aceb3300577feed9c94f
Reviewed-on: https://skia-review.googlesource.com/29521
Commit-Queue: Stan Iliev <stani@google.com>
Reviewed-by: Derek Sollenberger <djsollen@google.com>

2 files changed, 40 insertions, 0 deletions

diff --git a/include/android/SkAndroidFrameworkUtils.h b/include/android/SkAndroidFrameworkUtils.h
new file mode 100644
index 0000000000..0457d03534
--- /dev/null
+++ b/include/android/SkAndroidFrameworkUtils.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkAndroidFrameworkUtils_DEFINED
+#define SkAndroidFrameworkUtils_DEFINED
+
+#include "SkTypes.h"
+
+#ifdef SK_BUILD_FOR_ANDROID
+
+class SkCanvas;
+
+/**
+ *  SkAndroidFrameworkUtils expose private APIs used only by Android framework.
+ */
+class SkAndroidFrameworkUtils {
+public:
+
+#if SK_SUPPORT_GPU
+    /**
+     *  clipWithStencil draws the current clip into a stencil buffer with reference value and mask
+     *  set to 0x1. This function works only on a GPU canvas.
+     *
+     *  @param  canvas A GPU canvas that has a non-empty clip.
+     *
+     *  @return true on success or false if clip is empty or not a GPU canvas.
+     */
+    static bool clipWithStencil(SkCanvas* canvas);
+#endif //SK_SUPPORT_GPU
+};
+
+#endif // SK_BUILD_FOR_ANDROID
+
+#endif // SkAndroidFrameworkUtils_DEFINED
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index 8fbca71624..c4cb1752d8 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -17,6 +17,7 @@
 
 class GrContext;
 class GrRenderTargetContext;
+class SkAndroidFrameworkUtils;
 class SkBaseDevice;
 class SkBitmap;
 class SkClipStack;
@@ -1457,6 +1458,7 @@ private:
     void checkForDeferredSave();
     void internalSetMatrix(const SkMatrix&);
 
+    friend class SkAndroidFrameworkUtils;
     friend class SkDrawIter;        // needs setupDrawForLayerDevice()
     friend class AutoDrawLooper;
     friend class SkDebugCanvas;     // needs experimental fAllowSimplifyClip