[Shadows] Add shadow vertex generation code and shaders [8/n]

Bug: 136561771
Test: go/wm-smoke

Change-Id: I13e627a707d6d7a10bbd0ea6cc26bcb5c5bc9ab8
diff --git a/libs/renderengine/gl/GLSkiaShadowPort.h b/libs/renderengine/gl/GLSkiaShadowPort.h
new file mode 100644
index 0000000..e7d1861
--- /dev/null
+++ b/libs/renderengine/gl/GLSkiaShadowPort.h
@@ -0,0 +1,84 @@
+/*
+ * Copyright 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <math/vec4.h>
+#include <ui/Rect.h>
+
+namespace android {
+namespace renderengine {
+
+class Mesh;
+
+namespace gl {
+
+/**
+ * The shadow geometry logic and vertex generation code has been ported from skia shadow
+ * fast path OpenGL implementation to draw shadows around rects and rounded rects including
+ * circles.
+ *
+ * path: skia/src/gpu/GrRenderTargetContext.cpp GrRenderTargetContext::drawFastShadow
+ *
+ * Modifications made:
+ * - Switched to using std lib math functions
+ * - Fall off function is implemented in vertex shader rather than a shadow texture
+ * - Removed transformations applied on the caster rect since the caster will be in local
+ *   coordinate space and will be transformed by the vertex shader.
+ */
+
+enum RRectType {
+    kFill_RRectType,
+    kStroke_RRectType,
+    kOverstroke_RRectType,
+};
+
+struct Geometry {
+    vec4 fColor;
+    float fOuterRadius;
+    float fUmbraInset;
+    float fInnerRadius;
+    float fBlurRadius;
+    FloatRect fDevBounds;
+    RRectType fType;
+    bool fIsCircle;
+    bool fIsStroked;
+};
+
+std::unique_ptr<Geometry> getSpotShadowGeometry(const FloatRect& casterRect,
+                                                float casterCornerRadius, float casterZ,
+                                                bool casterIsTranslucent, const vec4& spotColor,
+                                                const vec3& lightPosition, float lightRadius);
+
+std::unique_ptr<Geometry> getAmbientShadowGeometry(const FloatRect& casterRect,
+                                                   float casterCornerRadius, float casterZ,
+                                                   bool casterIsTranslucent,
+                                                   const vec4& ambientColor);
+
+int getVertexCountForGeometry(const Geometry& shadowGeometry);
+
+int getIndexCountForGeometry(const Geometry& shadowGeometry);
+
+void fillVerticesForGeometry(const Geometry& shadowGeometry, int vertexCount,
+                             Mesh::VertexArray<vec2> position, Mesh::VertexArray<vec4> shadowColor,
+                             Mesh::VertexArray<vec3> shadowParams);
+
+void fillIndicesForGeometry(const Geometry& shadowGeometry, int indexCount,
+                            int startingVertexOffset, uint16_t* indices);
+
+} // namespace gl
+} // namespace renderengine
+} // namespace android