Reland a portion of r215672.

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 <cassert>
-#include <cstring>
-
-#include "gpu/demos/framework/demo.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>
-class Example : public gpu::demos::Demo {
- public:
-  Example()
-    : init_func_(NULL),
-      update_func_(NULL),
-      draw_func_(NULL),
-      shut_down_func_(NULL) {
-    esInitContext(&context_);
-    memset(&user_data_, 0, sizeof(UserData));
-    context_.userData = &user_data_;
-  }
-  virtual ~Example() {
-    shut_down_func_(&context_);
-  }
-
-  virtual bool InitGL() {
-    // Note that update_func is optional.
-    assert(init_func_ && draw_func_ && shut_down_func_);
-
-    if (!init_func_(&context_)) return false;
-    return true;
-  }
-
- protected:
-  void RegisterCallbacks(InitFunc* init_func,
-                         UpdateFunc* update_func,
-                         DrawFunc* draw_func,
-                         ShutDownFunc* shut_down_func) {
-    init_func_ = init_func;
-    update_func_ = update_func;
-    draw_func_ = draw_func;
-    shut_down_func_ = shut_down_func;
-  }
-
-  virtual void Render(float elapsed_sec) {
-    context_.width = width();
-    context_.height = height();
-
-    if (update_func_) update_func_(&context_, elapsed_sec);
-    draw_func_(&context_);
-  }
-
- private:
-  ESContext context_;
-  UserData user_data_;
-
-  // Callback functions.
-  InitFunc* init_func_;
-  UpdateFunc* update_func_;
-  DrawFunc* draw_func_;
-  ShutDownFunc* shut_down_func_;
-};
-
-}  // namespace gles2_book
-}  // namespace demos
-}  // namespace gpu
-#endif  // GPU_DEMOS_GLES2_BOOK_EXAMPLE_H_