[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/GLShadowVertexGenerator.h b/libs/renderengine/gl/GLShadowVertexGenerator.h
new file mode 100644
index 0000000..112f976
--- /dev/null
+++ b/libs/renderengine/gl/GLShadowVertexGenerator.h
@@ -0,0 +1,65 @@
+/*
+ * 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>
+
+#include "GLSkiaShadowPort.h"
+
+namespace android {
+namespace renderengine {
+
+class Mesh;
+
+namespace gl {
+
+/**
+ * Generates gl attributes required to draw shadow spot and/or ambient shadows.
+ *
+ * Each shadow can support different colors. This class generates three vertex attributes for
+ * each shadow, its position, color and shadow params(offset and distance). These can be sent
+ * using a single glDrawElements call.
+ */
+class GLShadowVertexGenerator {
+public:
+    GLShadowVertexGenerator(const FloatRect& casterRect, float casterCornerRadius, float casterZ,
+                            bool casterIsTranslucent, const vec4& ambientColor,
+                            const vec4& spotColor, const vec3& lightPosition, float lightRadius);
+    ~GLShadowVertexGenerator() = default;
+
+    size_t getVertexCount() const;
+    size_t getIndexCount() const;
+    void fillVertices(Mesh::VertexArray<vec2>& position, Mesh::VertexArray<vec4>& color,
+                      Mesh::VertexArray<vec3>& params) const;
+    void fillIndices(uint16_t* indices) const;
+
+private:
+    bool mDrawAmbientShadow;
+    std::unique_ptr<Geometry> mAmbientShadowGeometry;
+    int mAmbientShadowVertexCount = 0;
+    int mAmbientShadowIndexCount = 0;
+
+    bool mDrawSpotShadow;
+    std::unique_ptr<Geometry> mSpotShadowGeometry;
+    int mSpotShadowVertexCount = 0;
+    int mSpotShadowIndexCount = 0;
+};
+
+} // namespace gl
+} // namespace renderengine
+} // namespace android