Use MGLGetProcAddress to access OpenGL functions

examples/spinning_cube/spinning_cube.cc

 // Copyright 2013 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.
 
 // This example program is based on Simple_VertexShader.c from:
 
 //
 // Book:      OpenGL(R) ES 2.0 Programming Guide
 // Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
 // ISBN-10:   0321502795
 // ISBN-13:   9780321502797
 // Publisher: Addison-Wesley Professional
 // URLs:      http://safari.informit.com/9780321563835
 //            http://www.opengles-book.com
 //
 
 #include "examples/spinning_cube/spinning_cube.h"
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
 #include <math.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include "mojo/public/c/gpu/MGL/mgl.h"
 #include "mojo/public/cpp/environment/logging.h"
 
 namespace examples {
 
+#define VISIT_GL_CALL(Function, ReturnType, PARAMETERS, ARGUMENTS) \
+  typedef ReturnType (*Function##Type) PARAMETERS;

[jamesr, 2015/10/21 19:58:53]

nit: i find 'using' easier to read for function typedefs

[Petr Hosek, 2015/10/21 21:12:03]

Done.

+#include "mojo/public/platform/native/gles2/call_visitor_autogen.h"
+#undef VISIT_GL_CALL
+
+class SpinningCube::GLInterface {
+ private:

[jamesr, 2015/10/21 19:58:53]

style guide has an order for public / private, this should go lower

[Petr Hosek, 2015/10/21 21:12:03]

I need this to be defined before I declare the members. Shall I use multiple
public/private sections?

+  // This is a wrapper class that initializes pointer to nullptr.
+  template <typename T> class GLProcPtr {
+   public:
+    GLProcPtr() : ptr_(nullptr) {}
+    GLProcPtr operator=(T ptr) { ptr_ = ptr; return *this; }
+    operator T() const { return ptr_; }
+   private:
+    T ptr_;
+  };
+
+ public:
+  GLInterface() {}
+
+  void Init() {
+#define VISIT_GL_CALL(Function, ReturnType, PARAMETERS, ARGUMENTS) \
+    Function = reinterpret_cast<Function##Type>( \
+        MGLGetProcAddress("gl"#Function));
+#include "mojo/public/platform/native/gles2/call_visitor_autogen.h"
+#undef VISIT_GL_CALL
+  }
+
+#define VISIT_GL_CALL(Function, ReturnType, PARAMETERS, ARGUMENTS) \
+  GLProcPtr<Function##Type> Function;
+#include "mojo/public/platform/native/gles2/call_visitor_autogen.h"
+#undef VISIT_GL_CALL
+};
+
 namespace {
 
 const float kPi = 3.14159265359f;
 const int kNumVertices = 24;
 
-int GenerateCube(GLuint *vbo_vertices,
+int GenerateCube(const scoped_ptr<SpinningCube::GLInterface>& gl,
+                 GLuint *vbo_vertices,
                  GLuint *vbo_indices) {
   const int num_indices = 36;
 
   const GLfloat cube_vertices[kNumVertices * 3] = {
     // -Y side.
     -0.5f, -0.5f, -0.5f,
     -0.5f, -0.5f,  0.5f,
     0.5f, -0.5f,  0.5f,
     0.5f, -0.5f, -0.5f,
 
@@ skipping 86 matching lines @@
     // -X side.
     16, 17, 18,
     16, 18, 19,
 
     // +X side.
     20, 23, 22,
     20, 22, 21
   };
 
   if (vbo_vertices) {
-    glGenBuffers(1, vbo_vertices);
-    glBindBuffer(GL_ARRAY_BUFFER, *vbo_vertices);
-    glBufferData(GL_ARRAY_BUFFER,
+    gl->GenBuffers(1, vbo_vertices);
+    gl->BindBuffer(GL_ARRAY_BUFFER, *vbo_vertices);
+    gl->BufferData(GL_ARRAY_BUFFER,
                  sizeof(cube_vertices) + sizeof(vertex_normals),
                  nullptr,
                  GL_STATIC_DRAW);
-    glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(cube_vertices), cube_vertices);
-    glBufferSubData(GL_ARRAY_BUFFER, sizeof(cube_vertices),
+    gl->BufferSubData(GL_ARRAY_BUFFER, 0, sizeof(cube_vertices), cube_vertices);
+    gl->BufferSubData(GL_ARRAY_BUFFER, sizeof(cube_vertices),
                     sizeof(vertex_normals), vertex_normals);
-    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    gl->BindBuffer(GL_ARRAY_BUFFER, 0);
   }
 
   if (vbo_indices) {
-    glGenBuffers(1, vbo_indices);
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *vbo_indices);
-    glBufferData(GL_ELEMENT_ARRAY_BUFFER,
+    gl->GenBuffers(1, vbo_indices);
+    gl->BindBuffer(GL_ELEMENT_ARRAY_BUFFER, *vbo_indices);
+    gl->BufferData(GL_ELEMENT_ARRAY_BUFFER,
                  sizeof(cube_indices),
                  cube_indices,
                  GL_STATIC_DRAW);
-    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+    gl->BindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
   }
 
   return num_indices;
 }
 
-GLuint LoadShader(GLenum type,
+GLuint LoadShader(const scoped_ptr<SpinningCube::GLInterface>& gl,
+                  GLenum type,
                   const char* shader_source) {
-  GLuint shader = glCreateShader(type);
-  glShaderSource(shader, 1, &shader_source, NULL);
-  glCompileShader(shader);
+  GLuint shader = gl->CreateShader(type);
+  gl->ShaderSource(shader, 1, &shader_source, NULL);
+  gl->CompileShader(shader);
 
   GLint compiled = 0;
-  glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
+  gl->GetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
 
   if (!compiled) {
     GLsizei expected_length = 0;
-    glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &expected_length);
+    gl->GetShaderiv(shader, GL_INFO_LOG_LENGTH, &expected_length);
     std::string log;
     log.resize(expected_length);  // Includes null terminator.
     GLsizei actual_length = 0;
-    glGetShaderInfoLog(shader, expected_length, &actual_length, &log[0]);
+    gl->GetShaderInfoLog(shader, expected_length, &actual_length, &log[0]);
     log.resize(actual_length);  // Excludes null terminator.
     MOJO_LOG(FATAL) << "Compilation of shader failed: " << log;
-    glDeleteShader(shader);
+    gl->DeleteShader(shader);
     return 0;
   }
 
   return shader;
 }
 
-GLuint LoadProgram(const char* vertex_shader_source,
+GLuint LoadProgram(const scoped_ptr<SpinningCube::GLInterface>& gl,
+                   const char* vertex_shader_source,
                    const char* fragment_shader_source) {
-  GLuint vertex_shader = LoadShader(GL_VERTEX_SHADER,
+  GLuint vertex_shader = LoadShader(gl,
+                                    GL_VERTEX_SHADER,
                                     vertex_shader_source);
   if (!vertex_shader)
     return 0;
 
-  GLuint fragment_shader = LoadShader(GL_FRAGMENT_SHADER,
+  GLuint fragment_shader = LoadShader(gl,
+                                      GL_FRAGMENT_SHADER,
                                       fragment_shader_source);
   if (!fragment_shader) {
-    glDeleteShader(vertex_shader);
+    gl->DeleteShader(vertex_shader);
     return 0;
   }
 
-  GLuint program_object = glCreateProgram();
-  glAttachShader(program_object, vertex_shader);
-  glAttachShader(program_object, fragment_shader);
-  glLinkProgram(program_object);
-  glDeleteShader(vertex_shader);
-  glDeleteShader(fragment_shader);
+  GLuint program_object = gl->CreateProgram();
+  gl->AttachShader(program_object, vertex_shader);
+  gl->AttachShader(program_object, fragment_shader);
+  gl->LinkProgram(program_object);
+  gl->DeleteShader(vertex_shader);
+  gl->DeleteShader(fragment_shader);
 
   GLint linked = 0;
-  glGetProgramiv(program_object, GL_LINK_STATUS, &linked);
+  gl->GetProgramiv(program_object, GL_LINK_STATUS, &linked);
   if (!linked) {
     GLsizei expected_length = 0;
-    glGetProgramiv(program_object, GL_INFO_LOG_LENGTH, &expected_length);
+    gl->GetProgramiv(program_object, GL_INFO_LOG_LENGTH, &expected_length);
     std::string log;
     log.resize(expected_length);  // Includes null terminator.
     GLsizei actual_length = 0;
-    glGetProgramInfoLog(program_object, expected_length, &actual_length,
+    gl->GetProgramInfoLog(program_object, expected_length, &actual_length,
                         &log[0]);
     log.resize(actual_length);  // Excludes null terminator.
     MOJO_LOG(FATAL) << "Linking program failed: " << log;
-    glDeleteProgram(program_object);
+    gl->DeleteProgram(program_object);
     return 0;
   }
 
   return program_object;
 }
 
 class ESMatrix {
  public:
   GLfloat m[4][4];
 
@@ skipping 179 matching lines @@
   mvp_location_ = 0;
   vbo_vertices_ = 0;
   vbo_indices_ = 0;
   num_indices_ = 0;
 }
 
 SpinningCube::SpinningCube()
     : initialized_(false),
       width_(0),
       height_(0),
+      gl_(new GLInterface()),
       state_(new GLState()),
       fling_multiplier_(1.0f),
       direction_(1),
       color_() {
   state_->angle_ = 45.0f;
   set_color(1.0, 1.0, 1.0);
 }
 
 SpinningCube::~SpinningCube() {
   if (!initialized_)
     return;
   if (state_->vbo_vertices_)
-    glDeleteBuffers(1, &state_->vbo_vertices_);
+    gl_->DeleteBuffers(1, &state_->vbo_vertices_);
   if (state_->vbo_indices_)
-    glDeleteBuffers(1, &state_->vbo_indices_);
+    gl_->DeleteBuffers(1, &state_->vbo_indices_);
   if (state_->program_object_)
-    glDeleteProgram(state_->program_object_);
+    gl_->DeleteProgram(state_->program_object_);
 }
 
 void SpinningCube::Init() {
   const char vertex_shader_source[] =
       "uniform mat4 u_mvpMatrix;                                       \n"
       "attribute vec4 a_position;                                      \n"
       "attribute vec4 a_normal;                                        \n"
       "uniform vec3 u_color;                                           \n"
       "varying vec4 v_color;                                           \n"
       "void main()                                                     \n"
@@ skipping 10 matching lines @@
       "}                                                               \n";
 
   const char fragment_shader_source[] =
       "precision mediump float;                            \n"
       "varying vec4 v_color;                               \n"
       "void main()                                         \n"
       "{                                                   \n"
       "   gl_FragColor = v_color;                          \n"
       "}                                                   \n";
 
+  gl_->Init();
   state_->program_object_ = LoadProgram(
-      vertex_shader_source, fragment_shader_source);
-  state_->position_location_ = glGetAttribLocation(
+      gl_, vertex_shader_source, fragment_shader_source);
+  state_->position_location_ = gl_->GetAttribLocation(
       state_->program_object_, "a_position");
-  state_->normal_location_ = glGetAttribLocation(
+  state_->normal_location_ = gl_->GetAttribLocation(
       state_->program_object_, "a_normal");
-  state_->color_location_ = glGetUniformLocation(
+  state_->color_location_ = gl_->GetUniformLocation(
       state_->program_object_, "u_color");
-  state_->mvp_location_ = glGetUniformLocation(
+  state_->mvp_location_ = gl_->GetUniformLocation(
       state_->program_object_, "u_mvpMatrix");
   state_->num_indices_ = GenerateCube(
-      &state_->vbo_vertices_, &state_->vbo_indices_);
+      gl_, &state_->vbo_vertices_, &state_->vbo_indices_);
 
-  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
-  glEnable(GL_DEPTH_TEST);
+  gl_->ClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+  gl_->Enable(GL_DEPTH_TEST);
   initialized_ = true;
 }
 
 void SpinningCube::OnGLContextLost() {
   initialized_ = false;
   state_->OnGLContextLost();
 }
 
 void SpinningCube::SetFlingMultiplier(float drag_distance,
                                       float drag_time) {
@@ skipping 22 matching lines @@
 
 void SpinningCube::UpdateForDragDistance(float distance) {
   state_->angle_ += RotationForDragDistance(distance);
   if (state_->angle_ >= 360.0f )
     state_->angle_ -= 360.0f;
 
   Update();
 }
 
 void SpinningCube::Draw() {
-  glViewport(0, 0, width_, height_);
-  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
-  glUseProgram(state_->program_object_);
-  glBindBuffer(GL_ARRAY_BUFFER, state_->vbo_vertices_);
-  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, state_->vbo_indices_);
-  glVertexAttribPointer(state_->position_location_, 3, GL_FLOAT, GL_FALSE,
+  gl_->Viewport(0, 0, width_, height_);
+  gl_->Clear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+  gl_->UseProgram(state_->program_object_);
+  gl_->BindBuffer(GL_ARRAY_BUFFER, state_->vbo_vertices_);
+  gl_->BindBuffer(GL_ELEMENT_ARRAY_BUFFER, state_->vbo_indices_);
+  gl_->VertexAttribPointer(state_->position_location_, 3, GL_FLOAT, GL_FALSE,
                         3 * sizeof(GLfloat), 0);
-  glVertexAttribPointer(state_->normal_location_, 3, GL_FLOAT, GL_FALSE,
+  gl_->VertexAttribPointer(state_->normal_location_, 3, GL_FLOAT, GL_FALSE,
                         3 * sizeof(GLfloat),
                         reinterpret_cast<void*>(3 * sizeof(GLfloat) *
                                                 kNumVertices));
-  glEnableVertexAttribArray(state_->position_location_);
-  glEnableVertexAttribArray(state_->normal_location_);
-  glUniformMatrix4fv(state_->mvp_location_, 1, GL_FALSE,
+  gl_->EnableVertexAttribArray(state_->position_location_);
+  gl_->EnableVertexAttribArray(state_->normal_location_);
+  gl_->UniformMatrix4fv(state_->mvp_location_, 1, GL_FALSE,
                      static_cast<GLfloat*>(&state_->mvp_matrix_.m[0][0]));
-  glUniform3fv(state_->color_location_, 1, color_);
-  glDrawElements(GL_TRIANGLES, state_->num_indices_, GL_UNSIGNED_SHORT, 0);
+  gl_->Uniform3fv(state_->color_location_, 1, color_);
+  gl_->DrawElements(GL_TRIANGLES, state_->num_indices_, GL_UNSIGNED_SHORT, 0);
 }
 
 void SpinningCube::Update() {
   float aspect = static_cast<GLfloat>(width_) / static_cast<GLfloat>(height_);
 
   ESMatrix perspective;
   perspective.LoadIdentity();
   perspective.Perspective(60.0f, aspect, 1.0f, 20.0f );
 
   ESMatrix modelview;
   modelview.LoadIdentity();
   modelview.Translate(0.0, 0.0, -2.0);
   modelview.Rotate(state_->angle_ * direction_, 1.0, 0.0, 1.0);
 
   state_->mvp_matrix_.Multiply(&modelview, &perspective);
 }
 
 }  // namespace examples