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content/common/gpu/media/gles2_external_texture_copier.cc

+// Copyright (c) 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.
+
+#include "content/common/gpu/media/gles2_external_texture_copier.h"
+
+#include "base/logging.h"
+
+namespace content {
+
+static void CheckGlError(const char* op) {
+  for (GLint error = glGetError(); error; error = glGetError()) {
+    LOG(ERROR) << "after " << op <<" glError (0x" << std::hex << error << ")";
+    NOTREACHED();
+  }
+}
+
+static const char g_vertex_shader[] =
+    "uniform mat4 uMVPMatrix;\n"
+    "uniform mat4 uSTMatrix;\n"
+    "attribute vec4 aPosition;\n"
+    "attribute vec4 aTextureCoord;\n"
+    "varying vec2 vTextureCoord;\n"
+    "void main() {\n"
+    "  gl_Position = uMVPMatrix * aPosition;\n"
+    "  vTextureCoord = (uSTMatrix * aTextureCoord).xy;\n"
+    "}\n";
+
+static const char g_fragment_shader[] =
+    "#extension GL_OES_EGL_image_external : require\n"
+    "precision mediump float;\n"
+    "varying vec2 vTextureCoord;\n"
+    "uniform samplerExternalOES sTexture;\n"
+    "void main() {\n"
+    "  gl_FragColor = texture2D(sTexture, vTextureCoord);\n"
+    "}\n";
+
+static const int kVerticeStride = 5 * sizeof(float);

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

English: The singular of "vertices" is "vertex" ;)
I think in this case you want the plural though:
s/kVerticeStride/kVerticesStride/

+
+static const GLfloat g_vertices[] = {
+    -1.0f, -1.0f, 0, 0.f, 0.f,
+    1.0f, -1.0f, 0, 1.f, 0.f,
+    -1.0f, 1.0f, 0, 0.f, 1.f,
+    1.0f, 1.0f, 0, 1.f, 1.f,
+};
+
+// Due to the absence of matrix functions in NDK, a pre-calculated matrix
+// is used. g_mvp_matrix = P * L * I
+// Matrix.setLookAtM(L, 0, 0, 0, 2, 0, 0, 0, 0, -1, 0);
+// Matrix.orthoM(P, 0, -1, 1, -1, 1, 1, 3);
+// Matrix.setIdentityM(I, 0);
+// Up vector(0, -1, 0) is used instead of (0, 1, 0) to prevent flipped screen.
+static const GLfloat g_mvp_matrix[] = {

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

My glFoo is super-weak, but I believe what you have is equivalent to:
- drop uMVPMatrix (just use gl_position = aPosition in vertex shader)
- switch the 0's and 1's in the T coordinates in g_vertices; IOW the "Y" in
texture-coords.
This would save you l.47-59, I think.

+    1.f, 0.f, 0.f, 0.f,
+    0.f, -1.f, 0.f, 0.f,
+    0.f, 0.f, -1.f, 0.f,
+    0.f, 0.f, 0.f, 1.f,
+};
+
+static GLuint LoadShader(GLenum shaderType, const char* pSource) {

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

here and elsewhere, unix_style, not camelCase for variables & parameters.

(isn't it fun to work in both Java & C++ at the same time?!??!?)

+  GLuint shader = glCreateShader(shaderType);
+  if (shader) {

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

nit: if you reversed the test you could early-return and de-indent the rest of
the function.
Ditto for similar cases below.

+    glShaderSource(shader, 1, &pSource, NULL);
+    glCompileShader(shader);
+    GLint compiled = 0;
+    glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
+    if (!compiled) {
+      GLint infoLen = 0;
+      glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLen);
+      if (infoLen) {
+        char* buf = (char*) malloc(infoLen);

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

scoped_ptr

+        if (buf) {

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

unnecessary; malloc/new never fail in chromium other than by crashing the
process.

+          glGetShaderInfoLog(shader, infoLen, NULL, buf);
+          LOG(ERROR) << "Could not compile shader : " << buf;
+          free(buf);
+        }
+        glDeleteShader(shader);
+        shader = 0;
+      }
+    }
+  }
+  return shader;
+}
+
+static GLuint CreateProgram(
+    const char* pVertexSource, const char* pFragmentSource) {
+  GLuint vertexShader = LoadShader(GL_VERTEX_SHADER, pVertexSource);
+  if (!vertexShader)
+    return 0;
+
+  GLuint pixelShader = LoadShader(GL_FRAGMENT_SHADER, pFragmentSource);

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

s/pixel/fragment/ ?
(here and below)

+  if (!pixelShader)
+    return 0;
+
+  GLuint program = glCreateProgram();
+  if (program) {
+    glAttachShader(program, vertexShader);

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

delete the shaders after attaching them (so program has the only reference)

+    CheckGlError("glAttachShader");
+    glAttachShader(program, pixelShader);
+    CheckGlError("glAttachShader");
+    glLinkProgram(program);
+    GLint linkStatus = GL_FALSE;
+    glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
+    if (linkStatus != GL_TRUE) {
+      GLint bufLength = 0;
+      glGetProgramiv(program, GL_INFO_LOG_LENGTH, &bufLength);
+      if (bufLength) {
+        char* buf = (char*) malloc(bufLength);
+        if (buf) {
+          glGetProgramInfoLog(program, bufLength, NULL, buf);
+          LOG(ERROR) << "Could not link program: "<< buf;
+          free(buf);
+        }
+      }
+      glDeleteProgram(program);
+      program = 0;
+    }
+  }
+  return program;
+}
+
+Gles2ExternalTextureCopier::Gles2ExternalTextureCopier()
+  : initialized_(false),
+    width_(0),
+    height_(0),
+    framebuffer_id_(0),
+    renderbuffer_id_(0),
+    program_(0),
+    position_handle_(0),
+    st_matrix_handle_(0),
+    mvp_matrix_handle_(0),
+    texture_handle_(0),
+    previous_framebuffer_id_(0),
+    previous_renderbuffer_id_(0),
+    previous_texture_id_(0) {
+}
+
+Gles2ExternalTextureCopier::~Gles2ExternalTextureCopier() {
+  if (initialized_) {
+    glDeleteFramebuffersEXT(1, &framebuffer_id_);
+    glDeleteRenderbuffersEXT(1, &renderbuffer_id_);
+  }
+}
+
+bool Gles2ExternalTextureCopier::SetupGraphics() {
+  program_ = CreateProgram(g_vertex_shader, g_fragment_shader);
+  if (!program_) {
+    LOG(ERROR) << "Could not create program.";
+    return false;
+  }
+  position_handle_ = glGetAttribLocation(program_, "aPosition");
+  CheckGlError("glGetAttribLocation");
+
+  texture_handle_ = glGetAttribLocation(program_, "aTextureCoord");
+  CheckGlError("glGetAttribLocation aTextureCoord");
+
+  mvp_matrix_handle_ = glGetUniformLocation(program_, "uMVPMatrix");
+  CheckGlError("glGetUniformLocation uMVPMatrix");
+
+  st_matrix_handle_ = glGetUniformLocation(program_, "uSTMatrix");
+  CheckGlError("glGetUniformLocation uSTMatrix");
+
+  return true;
+}
+
+void Gles2ExternalTextureCopier::RenderFrame(
+    int w, int h, GLuint texture_id, const float transfrom_matrix[16]) {
+  glViewport(0, 0, w, h);

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

I suspect this can go in a Setup method

+  CheckGlError("glViewport");
+
+  glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

why DEPTH?
(IOW, why allocate a depthbuffer later?)

+  CheckGlError("glClear");
+
+  glUseProgram(program_);
+  CheckGlError("glUseProgram");
+
+  glActiveTexture(GL_TEXTURE0);
+  glBindTexture(GL_TEXTURE_EXTERNAL_OES, texture_id);
+  CheckGlError("glBindTexture");
+
+  glVertexAttribPointer(

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

l.181-195 can probably be done only once, right?  (when program_ is created)

+      position_handle_, 3, GL_FLOAT, GL_FALSE, kVerticeStride, g_vertices);
+  CheckGlError("glVertexAttribPointer vPositionHandle");
+  glEnableVertexAttribArray(position_handle_);
+  CheckGlError("glEnableVertexAttribArray vPositionHandle");
+
+  glVertexAttribPointer(
+      texture_handle_, 2, GL_FLOAT, GL_FALSE, kVerticeStride, g_vertices + 3);
+  CheckGlError("glVertexAttribPointer aTextureHandle");
+  glEnableVertexAttribArray(texture_handle_);
+  CheckGlError("glEnableVertexAttribArray aTextureHandle");
+
+  glUniformMatrix4fv(mvp_matrix_handle_, 1, GL_FALSE, g_mvp_matrix);
+  CheckGlError("glUniformMatrix4fv uMVPMatrixHandle");
+
+  glUniformMatrix4fv(st_matrix_handle_, 1, GL_FALSE, transfrom_matrix);

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

Part of me wants to just ignore transform_matrix and assume it's always a
vflip... :(

+  CheckGlError("glUniformMatrix4fv uSTMatrixHandle");
+
+  glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+  CheckGlError("glDrawArrays");
+}
+
+bool Gles2ExternalTextureCopier::Init(int32 width, int32 height) {
+  if (initialized_) {
+    LOG(ERROR) << "Init should not be called twice.";

[Ami GONE FROM CHROMIUM, 2013/02/17 00:12:44]

Since this is the only failure mode of Init(), I think it's confusing to make it
a separate API point.  Why not just inline it into the ctor?

But perhaps you meant to not discard the bool return values form the Setup*
functions?  

+    return false;
+  }
+
+  width_ = width;
+  height_ = height;
+
+  SaveState();
+  SetupGraphics();
+  SetupFrameBuffer();
+  RestoreState();
+
+  initialized_ = true;
+  return initialized_;
+}
+
+bool Gles2ExternalTextureCopier::Copy(
+    GLuint source_texture_id, GLuint destination_texture_id,
+    const float transfrom_matrix[16]) {
+  if (!initialized_)
+    return false;
+
+  SaveState();
+  glBindFramebufferEXT(GL_FRAMEBUFFER, framebuffer_id_);
+  glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                            destination_texture_id, 0);
+  GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER);
+  if (status != GL_FRAMEBUFFER_COMPLETE) {
+    LOG(ERROR) << "Framebuffer is not complete: " << status;
+    RestoreState();
+    return false;
+  }
+  CheckGlError("glBindFramebuffer framebuffer_id_");
+  RenderFrame(width_, height_, source_texture_id, transfrom_matrix);
+  RestoreState();
+
+  return true;
+}
+
+
+bool Gles2ExternalTextureCopier::SetupFrameBuffer() {
+  GLuint framebuffer;
+  glGenFramebuffersEXT(1, &framebuffer);
+  glBindFramebufferEXT(GL_FRAMEBUFFER, framebuffer);
+
+  GLuint depthbuffer;
+  glGenRenderbuffersEXT(1, &depthbuffer);
+
+  glBindRenderbufferEXT(GL_RENDERBUFFER, depthbuffer);
+  glRenderbufferStorageEXT(
+      GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width_, height_);
+  glFramebufferRenderbufferEXT(
+      GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthbuffer);
+  CheckGlError("glFramebufferRenderbuffer");
+
+  framebuffer_id_ = framebuffer;
+  renderbuffer_id_ = depthbuffer;
+  return true;
+}
+
+void Gles2ExternalTextureCopier::SaveState() {
+  glGetIntegerv(GL_FRAMEBUFFER_BINDING, (GLint *)&previous_framebuffer_id_);
+  CheckGlError("glGetIntegerv previous_framebuffer_id");
+  glGetIntegerv(GL_RENDERBUFFER_BINDING, (GLint *)&previous_renderbuffer_id_);
+  CheckGlError("glGetIntegerv previous_renderbuffer_id_");
+  glGetIntegerv(GL_TEXTURE_BINDING_2D, (GLint *)&previous_texture_id_);
+  CheckGlError("glGetIntegerv previous_texture_id_");
+}
+
+void Gles2ExternalTextureCopier::RestoreState() {
+  glBindFramebufferEXT(GL_FRAMEBUFFER, previous_framebuffer_id_);
+  CheckGlError("glBindFramebuffer previous_framebuffer_id");
+  glBindRenderbufferEXT(GL_RENDERBUFFER, previous_renderbuffer_id_);
+  CheckGlError("glBindFramebuffer previous_renderbuffer_id_");
+  glBindTexture(GL_TEXTURE_2D, previous_texture_id_);
+  CheckGlError("glBindTexture previous_texture_id_");
+}
+
+}  // namespace content