[Remoting] OpenGL Rendering Layer

remoting/client/gl_canvas.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 "remoting/client/gl_canvas.h"
+
+#include "base/logging.h"
+#include "remoting/client/gl_helpers.h"
+
+namespace {
+
+const int kVertexSize = 2;
+const int kVertexCount = 4;
+
+const char kTexCoordToViewVert[] =
+    // Region of the texture to be used (normally the whole texture).
+    "varying vec2 v_texCoord;\n"
+    "attribute vec2 a_texCoord;\n"
+
+    // Positions to draw the texture on the texture coordinates.
+    "attribute vec2 a_position;\n"
+    "uniform mat3 u_transform;\n"
+
+    // This matrix translates normalized texture coordinates
+    // ([0, 1] starting at upper-left corner) to the view coordinates
+    // ([-1, 1] starting at the center of the screen).
+    // Note that the matrix is defined in column-major order.
+    "const mat3 tex_to_view = mat3(2, 0, 0,\n"
+    "                              0, -2, 0,\n"
+    "                              -1, 1, 0);\n"
+    "void main() {\n"
+    "  v_texCoord = a_texCoord;\n"
+       // Transforms coordinates related to the canvas to coordinates
+       // related to the view.
+    "  vec3 trans_position = u_transform * vec3(a_position, 1.0);\n"
+       // Transforms texture coordinates to view coordinates and adds
+       // projection component 1.
+    "  gl_Position = vec4(tex_to_view * trans_position, 1.0);\n"
+    "}";
+
+const char kDrawTexFrag[] =
+    "precision mediump float;\n"
+
+    // Region on the texture to be used (normally the whole texture).
+    "varying vec2 v_texCoord;\n"
+    "uniform sampler2D u_texture;\n"
+    "void main() {\n"
+    "  gl_FragColor = texture2D(u_texture, v_texCoord);\n"
+    "}";
+
+}  // namespace
+
+namespace remoting {
+
+GlCanvas::GlCanvas(int gl_version) : gl_version_(gl_version) {
+  vertex_shader_ = CompileShader(GL_VERTEX_SHADER, kTexCoordToViewVert);
+  fragment_shader_ = CompileShader(GL_FRAGMENT_SHADER, kDrawTexFrag);
+  program_ = CreateProgram(vertex_shader_, fragment_shader_);
+  glUseProgram(program_);
+
+  transform_location_ = glGetUniformLocation(program_, "u_transform");
+  texture_location_ = glGetUniformLocation(program_, "u_texture");
+  position_location_ = glGetAttribLocation(program_, "a_position");
+  tex_cord_location_ = glGetAttribLocation(program_, "a_texCoord");
+  glEnableVertexAttribArray(position_location_);
+  glEnableVertexAttribArray(tex_cord_location_);
+  glEnable(GL_BLEND);
+  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+}
+
+GlCanvas::~GlCanvas() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  glDisable(GL_BLEND);
+  glDisableVertexAttribArray(tex_cord_location_);
+  glDisableVertexAttribArray(position_location_);
+  glDeleteProgram(program_);
+  glDeleteShader(vertex_shader_);
+  glDeleteShader(fragment_shader_);
+}
+
+void GlCanvas::SetNormalizedTransformation(const std::array<float, 9>& matrix) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  glUniformMatrix3fv(transform_location_, 1, GL_TRUE, matrix.data());
+  transformation_set_ = true;
+}
+
+void GlCanvas::DrawTexture(int texture_id,
+                           GLuint texture_handle,
+                           GLuint vertex_buffer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (!transformation_set_) {
+    return;
+  }
+  glActiveTexture(GL_TEXTURE0 + texture_id);
+  glBindTexture(GL_TEXTURE_2D, texture_handle);
+  glUniform1i(texture_location_, texture_id);
+  glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
+
+  glVertexAttribPointer(position_location_, kVertexSize, GL_FLOAT, GL_FALSE, 0,
+                        0);
+  glVertexAttribPointer(tex_cord_location_, kVertexSize, GL_FLOAT, GL_FALSE, 0,
+                        static_cast<float*>(0) + kVertexSize * kVertexCount);
+
+  glDrawArrays(GL_TRIANGLE_STRIP, 0, kVertexCount);
+  glBindBuffer(GL_ARRAY_BUFFER, 0);
+  glBindTexture(GL_TEXTURE_2D, 0);
+}
+
+int GlCanvas::GetGlVersion() const {
+  return gl_version_;
+}
+
+}  // namespace remoting