Created a base class for examples taken from gles2 book. It encapsulates the well-defined pattern followed by the examples to eliminate duplicated code. Once we finalize this CL, I will go ahead and change all demos to use this base class.

Review URL: http://codereview.chromium.org/543110

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@36542 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 90 insertions, 50 deletions

diff --git a/gpu/demos/gles2_book/example.h b/gpu/demos/gles2_book/example.h
new file mode 100644
index 0000000..839dfe3
--- /dev/null
+++ b/gpu/demos/gles2_book/example.h
@@ -0,0 +1,75 @@
+// 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_
diff --git a/gpu/demos/hello_triangle/main.cc b/gpu/demos/hello_triangle/main.cc
index 12a819b..3e45ffc 100644
--- a/gpu/demos/hello_triangle/main.cc
+++ b/gpu/demos/hello_triangle/main.cc
@@ -7,60 +7,25 @@
 // example is to demonstrate the basic concepts of
 // OpenGL ES 2.0 rendering.
 
-#include "gpu/demos/app_framework/application.h"
+#include "gpu/demos/gles2_book/example.h"
 #include "third_party/gles2_book/Chapter_2/Hello_Triangle/Hello_Triangle.h"
 
-namespace gpu_demos {
-class HelloTriangle : public Application {
- public:
-  HelloTriangle();
-  ~HelloTriangle();
-
-  bool Init();
-
- protected:
-  virtual void Draw(float elapsed_sec);
-
- private:
-  ESContext context_;
-  HTUserData user_data_;
-
-  DISALLOW_COPY_AND_ASSIGN(HelloTriangle);
-};
-
-HelloTriangle::HelloTriangle() {
-  esInitContext(&context_);
-
-  memset(&user_data_, 0, sizeof(HTUserData));
-  context_.userData = &user_data_;
-}
-
-HelloTriangle::~HelloTriangle() {
-  htShutDown(&context_);
-}
-
-bool HelloTriangle::Init() {
-  if (!Application::InitRenderContext()) return false;
-
-  context_.width = width();
-  context_.height = height();
-  if (!htInit(&context_)) return false;
-
-  return true;
-}
-
-void HelloTriangle::Draw(float /*elapsed_sec*/) {
-  htDraw(&context_);
-}
-}  // namespace gpu_demos
+namespace gpu {
+namespace demos {
+namespace gles2_book {
+typedef Example<HTUserData,
+                htInit,
+                NoOpUpdateFunc,
+                htDraw,
+                htShutDown> HelloTriangle;
+}  // namespace gles2_book
+}  // namespace demos
+}  // namespace gpu
 
 int main(int argc, char *argv[]) {
-  gpu_demos::HelloTriangle app;
-  if (!app.Init()) {
-    printf("Could not init.\n");
-    return EXIT_FAILURE;
-  }
+  gpu::demos::gles2_book::HelloTriangle demo;
+  CHECK(demo.Init());
 
-  app.MainLoop();
+  demo.MainLoop();
   return EXIT_SUCCESS;
 }