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>

1 files changed, 56 insertions, 0 deletions

diff --git a/src/android/SkAndroidFrameworkUtils.cpp b/src/android/SkAndroidFrameworkUtils.cpp
new file mode 100644
index 0000000000..5fbc2cae18
--- /dev/null
+++ b/src/android/SkAndroidFrameworkUtils.cpp
@@ -0,0 +1,56 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkAndroidFrameworkUtils.h"
+#include "SkCanvas.h"
+#include "SkDevice.h"
+
+#if SK_SUPPORT_GPU
+#include "GrStyle.h"
+#include "GrClip.h"
+#include "GrRenderTargetContext.h"
+#include "GrUserStencilSettings.h"
+#include "effects/GrDisableColorXP.h"
+#endif //SK_SUPPORT_GPU
+
+#ifdef SK_BUILD_FOR_ANDROID
+
+#if SK_SUPPORT_GPU
+bool SkAndroidFrameworkUtils::clipWithStencil(SkCanvas* canvas) {
+    SkRegion clipRegion;
+    canvas->temporary_internal_getRgnClip(&clipRegion);
+    if (clipRegion.isEmpty()) {
+        return false;
+    }
+    SkBaseDevice* device = canvas->getDevice();
+    if (!device) {
+        return false;
+    }
+    GrRenderTargetContext* rtc = device->accessRenderTargetContext();
+    if (!rtc) {
+        return false;
+    }
+    GrPaint grPaint;
+    grPaint.setXPFactory(GrDisableColorXPFactory::Get());
+    GrNoClip noClip;
+    static constexpr GrUserStencilSettings kDrawToStencil(
+        GrUserStencilSettings::StaticInit<
+            0x1,
+            GrUserStencilTest::kAlways,
+            0x1,
+            GrUserStencilOp::kReplace,
+            GrUserStencilOp::kReplace,
+            0x1>()
+    );
+    rtc->drawRegion(noClip, std::move(grPaint), GrAA::kNo, SkMatrix::I(), clipRegion,
+                    GrStyle::SimpleFill(), &kDrawToStencil);
+    return true;
+}
+#endif //SK_SUPPORT_GPU
+
+#endif // SK_BUILD_FOR_ANDROID
+