Introduce ChromeVR to Chrome on Android (behind a build flag)

chrome/browser/android/vr_shell/vr_shell_renderer.cc

+// Copyright 2016 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.
+
+#include "chrome/browser/android/vr_shell/vr_shell_renderer.h"
+
+#include "chrome/browser/android/vr_shell/vr_util.h"
+
+namespace vr_shell {
+
+namespace {
+
+const float kHalfHeight = 0.5f;
+const float kHalfWidth = 0.5f;
+const float kTextureQuadPosition[18] = {
+    -kHalfWidth, kHalfHeight,  0.0f, -kHalfWidth, -kHalfHeight, 0.0f,
+    kHalfWidth,  kHalfHeight,  0.0f, -kHalfWidth, -kHalfHeight, 0.0f,
+    kHalfWidth,  -kHalfHeight, 0.0f, kHalfWidth,  kHalfHeight,  0.0f
+};
+const int kPositionDataSize = 3;
+// Number of vertices passed to glDrawArrays().
+const int kVerticesNumber = 6;
+
+const float kTexturedQuadTextureCoordinates[12] = {
+    0.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f,
+    0.0f, 1.0f, 1.0f, 1.0f, 1.0f, 0.0f
+};
+const int kTextureCoordinateDataSize = 2;
+
+const GLchar* kTexturedQuadVertexShader =

[bajones, 2016/08/19 17:29:43]

Minor suggestion, not blocking: There's a reasonably nice pattern for declaring
shader code that you can see at
https://cs.chromium.org/chromium/src/gpu/tools/compositor_model_bench/shaders...
It allows you to avoid all the "\n" gunk and makes the actual shader text more
readable. I suggest using it here.

[bshe, 2016/08/19 21:05:10]

Done.

+    "uniform mat4 u_CombinedMatrix;\n"
+    "attribute vec4 a_Position;\n"
+    "attribute vec2 a_TexCoordinate;\n"
+    "varying vec2 v_TexCoordinate;\n"
+    "\n"
+    "void main() {\n"
+    "  v_TexCoordinate = a_TexCoordinate;\n"
+    "  gl_Position = u_CombinedMatrix * a_Position;\n"
+    "}\n";
+
+const GLchar* kTexturedQuadFragmentShader =
+    "#extension GL_OES_EGL_image_external : require\n"
+    "precision highp float;\n"
+    "uniform samplerExternalOES u_Texture;\n"
+    "varying vec2 v_TexCoordinate;\n"
+    "\n"
+    "void main() {\n"
+    "  vec4 texture = texture2D(u_Texture, v_TexCoordinate);\n"
+    "  gl_FragColor = vec4(texture.r, texture.g, texture.b, 1.0);\n"
+    "}\n";
+
+}  // namespace
+
+TexturedQuadRenderer::TexturedQuadRenderer() {
+  std::string error;
+  vertex_shader_handle_ =
+      CompileShader(GL_VERTEX_SHADER, kTexturedQuadVertexShader, error);
+  if (vertex_shader_handle_ == 0) {
+    LOG(ERROR) << error;
+    exit(1);
+  }
+  fragment_shader_handle_ =
+      CompileShader(GL_FRAGMENT_SHADER, kTexturedQuadFragmentShader, error);
+  if (fragment_shader_handle_ == 0) {
+    LOG(ERROR) << error;
+    exit(1);
+  }
+
+  program_handle_ = CreateAndLinkProgram(
+      vertex_shader_handle_, fragment_shader_handle_, 4, nullptr, error);
+  if (program_handle_ == 0) {
+    LOG(ERROR) << error;
+    exit(1);
+  }
+  combined_matrix_handle_ =
+      glGetUniformLocation(program_handle_, "u_CombinedMatrix");
+  texture_uniform_handle_ = glGetUniformLocation(program_handle_, "u_Texture");
+  position_handle_ = glGetAttribLocation(program_handle_, "a_Position");
+  texture_coordinate_handle_ =
+      glGetAttribLocation(program_handle_, "a_TexCoordinate");
+}
+
+void TexturedQuadRenderer::Draw(int texture_data_handle,
+                                const gvr::Mat4f& combined_matrix) {
+  glUseProgram(program_handle_);
+
+  // Pass in model view project matrix.
+  glUniformMatrix4fv(combined_matrix_handle_, 1, false,
+                     MatrixToGLArray(combined_matrix).data());
+
+  // Pass in texture coordinate.
+  glVertexAttribPointer(texture_coordinate_handle_, kTextureCoordinateDataSize,
+                        GL_FLOAT, false, 0, kTexturedQuadTextureCoordinates);
+  glEnableVertexAttribArray(texture_coordinate_handle_);
+
+  glVertexAttribPointer(position_handle_, kPositionDataSize, GL_FLOAT, false, 0,
+                        kTextureQuadPosition);
+  glEnableVertexAttribArray(position_handle_);
+
+  // Link texture data with texture unit.
+  glActiveTexture(GL_TEXTURE0);
+  glBindTexture(GL_TEXTURE_EXTERNAL_OES, texture_data_handle);
+  glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+  glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+  glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+  glUniform1i(texture_uniform_handle_, 0);
+
+  glDrawArrays(GL_TRIANGLES, 0, kVerticesNumber);
+
+  glDisableVertexAttribArray(position_handle_);
+  glDisableVertexAttribArray(texture_coordinate_handle_);
+}
+
+TexturedQuadRenderer::~TexturedQuadRenderer() {
+  glDeleteShader(vertex_shader_handle_);
+  glDeleteShader(fragment_shader_handle_);
+}
+
+VrShellRenderer::VrShellRenderer()
+    : textured_quad_renderer_(new TexturedQuadRenderer) {}
+
+VrShellRenderer::~VrShellRenderer() {}
+
+}  // namespace vr_shell