[PPAPI] Compositor API implementation

ppapi/examples/compositor/spinning_cube.cc

Index: ppapi/examples/compositor/spinning_cube.cc
diff --git a/ppapi/examples/compositor/spinning_cube.cc b/ppapi/examples/compositor/spinning_cube.cc
new file mode 100644
index 0000000000000000000000000000000000000000..2e76699c04609a3a7e47ea627840e2c2e4de0788
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+++ b/ppapi/examples/compositor/spinning_cube.cc
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+// Copyright 2014 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 "ppapi/examples/compositor/spinning_cube.h"
+
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <algorithm>
+
+#include "ppapi/lib/gl/include/GLES2/gl2.h"
+
+namespace {
+
+const float kPi = 3.14159265359f;
+
+int GenerateCube(GLuint *vbo_vertices,
+                 GLuint *vbo_indices) {
+  const int num_indices = 36;
+
+  const GLfloat cube_vertices[] = {
+    -0.5f, -0.5f, -0.5f,
+     0.5f, -0.5f, -0.5f,
+     0.5f, -0.5f,  0.5f,
+    -0.5f, -0.5f,  0.5f,
+    -0.5f,  0.5f, -0.5f,
+     0.5f,  0.5f, -0.5f,
+     0.5f,  0.5f,  0.5f,
+    -0.5f,  0.5f,  0.5f,
+  };
+
+  const GLushort cube_indices[] = {
+    0, 2, 1,
+    0, 3, 2,
+    4, 5, 6,
+    4, 6, 7,
+    3, 6, 2,
+    3, 7, 6,
+    0, 1, 5,
+    0, 5, 4,
+    0, 7, 3,
+    0, 4, 7,
+    1, 2, 6,
+    1, 6, 5,
+  };
+
+  if (vbo_vertices) {
+    glGenBuffers(1, vbo_vertices);
+    glBindBuffer(GL_ARRAY_BUFFER, *vbo_vertices);
+    glBufferData(GL_ARRAY_BUFFER,
+                 sizeof(cube_vertices),
+                 cube_vertices,
+                 GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+  }
+
+  if (vbo_indices) {
+    glGenBuffers(1, vbo_indices);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *vbo_indices);
+    glBufferData(GL_ELEMENT_ARRAY_BUFFER,
+                 sizeof(cube_indices),
+                 cube_indices,
+                 GL_STATIC_DRAW);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+  }
+
+  return num_indices;
+}
+
+GLuint LoadShader(GLenum type,
+                  const char* shader_source) {
+  GLuint shader = glCreateShader(type);
+  glShaderSource(shader, 1, &shader_source, NULL);
+  glCompileShader(shader);
+
+  GLint compiled = 0;
+  glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
+
+  if (!compiled) {
+    glDeleteShader(shader);
+    return 0;
+  }
+
+  return shader;
+}
+
+GLuint LoadProgram(const char* vertext_shader_source,
+                   const char* fragment_shader_source) {
+  GLuint vertex_shader = LoadShader(GL_VERTEX_SHADER,
+                                    vertext_shader_source);
+  if (!vertex_shader)
+    return 0;
+
+  GLuint fragment_shader = LoadShader(GL_FRAGMENT_SHADER,
+                                      fragment_shader_source);
+  if (!fragment_shader) {
+    glDeleteShader(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);
+
+  GLint linked = 0;
+  glGetProgramiv(program_object, GL_LINK_STATUS, &linked);
+
+  if (!linked) {
+    glDeleteProgram(program_object);
+    return 0;
+  }
+
+  return program_object;
+}
+
+class ESMatrix {
+ public:
+  GLfloat m[4][4];
+
+  ESMatrix() {
+    LoadZero();
+  }
+
+  void LoadZero() {
+    memset(this, 0x0, sizeof(ESMatrix));
+  }
+
+  void LoadIdentity() {
+    LoadZero();
+    m[0][0] = 1.0f;
+    m[1][1] = 1.0f;
+    m[2][2] = 1.0f;
+    m[3][3] = 1.0f;
+  }
+
+  void Multiply(ESMatrix* a, ESMatrix* b) {
+    ESMatrix result;
+    for (int i = 0; i < 4; ++i) {
+      result.m[i][0] = (a->m[i][0] * b->m[0][0]) +
+                       (a->m[i][1] * b->m[1][0]) +
+                       (a->m[i][2] * b->m[2][0]) +
+                       (a->m[i][3] * b->m[3][0]);
+
+      result.m[i][1] = (a->m[i][0] * b->m[0][1]) +
+                       (a->m[i][1] * b->m[1][1]) +
+                       (a->m[i][2] * b->m[2][1]) +
+                       (a->m[i][3] * b->m[3][1]);
+
+      result.m[i][2] = (a->m[i][0] * b->m[0][2]) +
+                       (a->m[i][1] * b->m[1][2]) +
+                       (a->m[i][2] * b->m[2][2]) +
+                       (a->m[i][3] * b->m[3][2]);
+
+      result.m[i][3] = (a->m[i][0] * b->m[0][3]) +
+                       (a->m[i][1] * b->m[1][3]) +
+                       (a->m[i][2] * b->m[2][3]) +
+                       (a->m[i][3] * b->m[3][3]);
+    }
+    *this = result;
+  }
+
+  void Frustum(float left,
+               float right,
+               float bottom,
+               float top,
+               float near_z,
+               float far_z) {
+    float delta_x = right - left;
+    float delta_y = top - bottom;
+    float delta_z = far_z - near_z;
+
+    if ((near_z <= 0.0f) ||
+        (far_z <= 0.0f) ||
+        (delta_z <= 0.0f) ||
+        (delta_y <= 0.0f) ||
+        (delta_y <= 0.0f))
+      return;
+
+    ESMatrix frust;
+    frust.m[0][0] = 2.0f * near_z / delta_x;
+    frust.m[0][1] = frust.m[0][2] = frust.m[0][3] = 0.0f;
+
+    frust.m[1][1] = 2.0f * near_z / delta_y;
+    frust.m[1][0] = frust.m[1][2] = frust.m[1][3] = 0.0f;
+
+    frust.m[2][0] = (right + left) / delta_x;
+    frust.m[2][1] = (top + bottom) / delta_y;
+    frust.m[2][2] = -(near_z + far_z) / delta_z;
+    frust.m[2][3] = -1.0f;
+
+    frust.m[3][2] = -2.0f * near_z * far_z / delta_z;
+    frust.m[3][0] = frust.m[3][1] = frust.m[3][3] = 0.0f;
+
+    Multiply(&frust, this);
+  }
+
+  void Perspective(float fov_y, float aspect, float near_z, float far_z) {
+    GLfloat frustum_h = tanf(fov_y / 360.0f * kPi) * near_z;
+    GLfloat frustum_w = frustum_h * aspect;
+    Frustum(-frustum_w, frustum_w, -frustum_h, frustum_h, near_z, far_z);
+  }
+
+  void Translate(GLfloat tx, GLfloat ty, GLfloat tz) {
+    m[3][0] += m[0][0] * tx + m[1][0] * ty + m[2][0] * tz;
+    m[3][1] += m[0][1] * tx + m[1][1] * ty + m[2][1] * tz;
+    m[3][2] += m[0][2] * tx + m[1][2] * ty + m[2][2] * tz;
+    m[3][3] += m[0][3] * tx + m[1][3] * ty + m[2][3] * tz;
+  }
+
+  void Rotate(GLfloat angle, GLfloat x, GLfloat y, GLfloat z) {
+    GLfloat mag = sqrtf(x * x + y * y + z * z);
+
+    GLfloat sin_angle = sinf(angle * kPi / 180.0f);
+    GLfloat cos_angle = cosf(angle * kPi / 180.0f);
+    if (mag > 0.0f) {
+      GLfloat xx, yy, zz, xy, yz, zx, xs, ys, zs;
+      GLfloat one_minus_cos;
+      ESMatrix rotation;
+
+      x /= mag;
+      y /= mag;
+      z /= mag;
+
+      xx = x * x;
+      yy = y * y;
+      zz = z * z;
+      xy = x * y;
+      yz = y * z;
+      zx = z * x;
+      xs = x * sin_angle;
+      ys = y * sin_angle;
+      zs = z * sin_angle;
+      one_minus_cos = 1.0f - cos_angle;
+
+      rotation.m[0][0] = (one_minus_cos * xx) + cos_angle;
+      rotation.m[0][1] = (one_minus_cos * xy) - zs;
+      rotation.m[0][2] = (one_minus_cos * zx) + ys;
+      rotation.m[0][3] = 0.0F;
+
+      rotation.m[1][0] = (one_minus_cos * xy) + zs;
+      rotation.m[1][1] = (one_minus_cos * yy) + cos_angle;
+      rotation.m[1][2] = (one_minus_cos * yz) - xs;
+      rotation.m[1][3] = 0.0F;
+
+      rotation.m[2][0] = (one_minus_cos * zx) - ys;
+      rotation.m[2][1] = (one_minus_cos * yz) + xs;
+      rotation.m[2][2] = (one_minus_cos * zz) + cos_angle;
+      rotation.m[2][3] = 0.0F;
+
+      rotation.m[3][0] = 0.0F;
+      rotation.m[3][1] = 0.0F;
+      rotation.m[3][2] = 0.0F;
+      rotation.m[3][3] = 1.0F;
+
+      Multiply(&rotation, this);
+    }
+  }
+};
+
+float RotationForTimeDelta(float delta_time) {
+  return delta_time * 40.0f;
+}
+
+float RotationForDragDistance(float drag_distance) {
+  return drag_distance / 5; // Arbitrary damping.
+}
+
+}  // namespace
+
+class SpinningCube::GLState {
+ public:
+  GLState();
+
+  void OnGLContextLost();
+
+  GLfloat angle_;  // Survives losing the GL context.
+
+  GLuint program_object_;
+  GLint position_location_;
+  GLint mvp_location_;
+  GLuint vbo_vertices_;
+  GLuint vbo_indices_;
+  int num_indices_;
+  ESMatrix mvp_matrix_;
+};
+
+SpinningCube::GLState::GLState()
+    : angle_(0) {
+  OnGLContextLost();
+}
+
+void SpinningCube::GLState::OnGLContextLost() {
+  program_object_ = 0;
+  position_location_ = 0;
+  mvp_location_ = 0;
+  vbo_vertices_ = 0;
+  vbo_indices_ = 0;
+  num_indices_ = 0;
+}
+
+SpinningCube::SpinningCube()
+    : initialized_(false),
+      width_(0),
+      height_(0),
+      state_(new GLState()),
+      fling_multiplier_(1.0f),
+      direction_(1) {
+  state_->angle_ = 45.0f;
+}
+
+SpinningCube::~SpinningCube() {
+  if (!initialized_)
+    return;
+  if (state_->vbo_vertices_)
+    glDeleteBuffers(1, &state_->vbo_vertices_);
+  if (state_->vbo_indices_)
+    glDeleteBuffers(1, &state_->vbo_indices_);
+  if (state_->program_object_)
+    glDeleteProgram(state_->program_object_);
+
+  delete state_;
+}
+
+void SpinningCube::Init(uint32_t width, uint32_t height) {
+  width_ = width;
+  height_ = height;
+
+  if (!initialized_) {
+    initialized_ = true;
+    const char vertext_shader_source[] =
+        "uniform mat4 u_mvpMatrix;                   \n"
+        "attribute vec4 a_position;                  \n"
+        "varying vec4 v_color;                       \n"
+        "void main()                                 \n"
+        "{                                           \n"
+        "   gl_Position = u_mvpMatrix * a_position;  \n"
+        "   v_color = vec4(a_position.x + 0.5,       \n"
+        "                  a_position.y + 0.5,       \n"
+        "                  a_position.z + 0.5,       \n"
+        "                  0.8);                     \n"
+        "}                                           \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";
+
+    state_->program_object_ = LoadProgram(
+        vertext_shader_source, fragment_shader_source);
+    state_->position_location_ = glGetAttribLocation(
+        state_->program_object_, "a_position");
+    state_->mvp_location_ = glGetUniformLocation(
+        state_->program_object_, "u_mvpMatrix");
+    state_->num_indices_ = GenerateCube(&state_->vbo_vertices_,
+                                        &state_->vbo_indices_);
+
+    glClearColor(0.0f, 0.0f, 0.0f, 0.2f);
+  }
+}
+
+void SpinningCube::OnGLContextLost() {
+  // TODO(yzshen): Is it correct that in this case we don't need to do cleanup
+  // for program and buffers?
+  initialized_ = false;
+  height_ = 0;
+  width_ = 0;
+  state_->OnGLContextLost();
+}
+
+void SpinningCube::SetFlingMultiplier(float drag_distance,
+                                      float drag_time) {
+  fling_multiplier_ = RotationForDragDistance(drag_distance) /
+      RotationForTimeDelta(drag_time);
+
+}
+
+void SpinningCube::UpdateForTimeDelta(float delta_time) {
+  state_->angle_ += RotationForTimeDelta(delta_time) * fling_multiplier_;
+  if (state_->angle_ >= 360.0f)
+    state_->angle_ -= 360.0f;
+
+  // Arbitrary 50-step linear reduction in spin speed.
+  if (fling_multiplier_ > 1.0f) {
+    fling_multiplier_ =
+        std::max(1.0f, fling_multiplier_ - (fling_multiplier_ - 1.0f) / 50);
+  }
+
+  Update();
+}
+
+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);
+  glEnable(GL_DEPTH_TEST);
+  glUseProgram(state_->program_object_);
+
+  glBindBuffer(GL_ARRAY_BUFFER, state_->vbo_vertices_);
+  glVertexAttribPointer(state_->position_location_,
+                        3,
+                        GL_FLOAT,
+                        GL_FALSE, 3 * sizeof(GLfloat),
+                        0);
+  glEnableVertexAttribArray(state_->position_location_);
+
+  glUniformMatrix4fv(state_->mvp_location_,
+                     1,
+                     GL_FALSE,
+                     (GLfloat*) &state_->mvp_matrix_.m[0][0]);
+  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, state_->vbo_indices_);
+  glDrawElements(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);
+}