Created a base class for examples taken from gles2 book. It encapsulates the ...

gpu/demos/gles2_book/example.h

+// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Base class for OpenGL ES 2.0 book examples.
+
+#ifndef GPU_DEMOS_GLES2_BOOK_EXAMPLE_H_
+#define GPU_DEMOS_GLES2_BOOK_EXAMPLE_H_
+
+#include "gpu/demos/app_framework/application.h"
+#include "third_party/gles2_book/Common/Include/esUtil.h"
+
+namespace gpu {
+namespace demos {
+namespace gles2_book {
+
+typedef int InitFunc(ESContext* context);
+typedef void UpdateFunc(ESContext* context, float elapsed_sec);
+typedef void DrawFunc(ESContext* context);
+typedef void ShutDownFunc(ESContext* context);
+
+// The examples taken from OpenGL 2.0 ES book follow a well-defined pattern.
+// They all use one ESContext that holds a reference to a custom UserData.
+// Each example provides four functions:
+// 1. InitFunc to initialize OpenGL state and custom UserData
+// 2. UpdateFunc is called before drawing each frame to update animation etc.
+// 3. DrawFunc is called to do the actual frame rendering
+// 4. ShutDownFunc is called when program terminates
+// This class encapsulates this pattern to make it easier to write classes
+// for each example.
+template <typename UserData,
+          InitFunc init_func,
+          UpdateFunc update_func,
+          DrawFunc draw_func,
+          ShutDownFunc shut_down_func>
+class Example : public gpu_demos::Application {
+ public:
+  Example() {
+    esInitContext(&context_);
+    memset(&user_data_, 0, sizeof(UserData));
+    context_.userData = &user_data_;
+  }
+  virtual ~Example() {
+    shut_down_func(&context_);
+  }
+
+  bool Init() {
+    if (!InitRenderContext()) return false;
+
+    context_.width = width();
+    context_.height = height();
+    if (!init_func(&context_)) return false;
+    return true;
+  }
+
+ protected:
+  virtual void Draw(float elapsed_sec) {
+    update_func(&context_, elapsed_sec);
+    draw_func(&context_);
+  }
+
+ private:
+  ESContext context_;
+  UserData user_data_;
+  DISALLOW_COPY_AND_ASSIGN(Example);
+};
+
+// Many examples do need to update anything and hence do not provide an
+// update function. This no-op function can be used for such examples.
+inline void NoOpUpdateFunc(ESContext* context, float elapsed_sec) {}
+
+}  // namespace gles2_book
+}  // namespace demos
+}  // namespace gpu
+#endif  // GPU_DEMOS_GLES2_BOOK_EXAMPLE_H_