Move Android shadow rendering interface to util library.

BUG=skia:6119

Change-Id: I8318cf2758042ffd0c81c5fa74240acbf7bea61f
Reviewed-on: https://skia-review.googlesource.com/6999
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

2 files changed, 52 insertions, 1 deletions

diff --git a/src/effects/SkShadowMaskFilter.cpp b/src/effects/SkShadowMaskFilter.cpp
index f1012f5e0f..61a93b8982 100755
--- a/src/effects/SkShadowMaskFilter.cpp
+++ b/src/effects/SkShadowMaskFilter.cpp
@@ -234,7 +234,7 @@ bool SkShadowMaskFilterImpl::directFilterRRectMaskGPU(GrContext*,
         static const float kGeomFactor = 64.0f;
 
         SkScalar srcSpaceAmbientRadius = fOccluderHeight * kHeightFactor * kGeomFactor;
-        const float umbraAlpha = 1.0f / (1.0f + SkTMax(fOccluderHeight * kHeightFactor, 0.0f));
+        const float umbraAlpha = (1.0f + SkTMax(fOccluderHeight * kHeightFactor, 0.0f));
         const SkScalar ambientOffset = srcSpaceAmbientRadius * umbraAlpha;
 
         // For the ambient rrect, we inset the offset rect by half the srcSpaceAmbientRadius
diff --git a/src/effects/SkShadowMaskFilter.h b/src/effects/SkShadowMaskFilter.h
new file mode 100755
index 0000000000..a85da63db9
--- /dev/null
+++ b/src/effects/SkShadowMaskFilter.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkShadowMaskFilter_DEFINED
+#define SkShadowMaskFilter_DEFINED
+
+#include "SkMaskFilter.h"
+
+
+/*
+ * This filter implements a pair of shadows for an occluding object-- one representing
+ * ambient occlusion, and one representing a displaced shadow from a point light.
+ */
+class SK_API SkShadowMaskFilter {
+public:
+    enum ShadowFlags {
+        kNone_ShadowFlag = 0x00,
+        /** The occluding object is not opaque. Knowing that the occluder is opaque allows
+          * us to cull shadow geometry behind it and improve performance. */
+        kTransparentOccluder_ShadowFlag = 0x01,
+        /** Use a larger umbra for a darker shadow */
+        kLargerUmbra_ShadowFlag = 0x02,
+        /** Use a Gaussian for the edge function rather than smoothstep */
+        kGaussianEdge_ShadowFlag = 0x04,
+        /** mask for all shadow flags */
+        kAll_ShadowFlag = 0x07
+    };
+
+    /** Create a shadow maskfilter.
+     *  @param occluderHeight Height of occluding object off of ground plane.
+     *  @param lightPos       Position of the light applied to this object.
+     *  @param lightRadius    Radius of the light (light is assumed to be spherical).
+     *  @param ambientAlpha   Base opacity of the ambient occlusion shadow.
+     *  @param spotAlpha      Base opacity of the displaced spot shadow.
+     *  @param flags          Flags to use - defaults to none
+     *  @return The new shadow maskfilter
+     */
+    static sk_sp<SkMaskFilter> Make(SkScalar occluderHeight, const SkPoint3& lightPos,
+                                    SkScalar lightRadius, SkScalar ambientAlpha,
+                                    SkScalar spotAlpha, uint32_t flags = kNone_ShadowFlag);
+
+    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
+
+private:
+    SkShadowMaskFilter(); // can't be instantiated
+};
+#endif