Add an occlusion query to count shaded fragments

README.md

 
 ## Instructions
 - Enter the CrOS chroot and set up the boards you want to test against (`setup_board --board=${BOARD}`). 
-- Emerge mesa, and libpng to the device under test (`emerge media-libs/mesa libpng && cros deploy ${IP_ADDR} ${PACKAGES}`).
+- Emerge mesa, and libpng to the device under test (`emerge x11-drivers/opengles-headers media-libs/mesa libpng && cros deploy ${IP_ADDR} ${PACKAGES}`).
 - `make shaders`
 - `target={local, atlas (i915), cheza (adreno)} make`

occlusion.cc

 #include <png.h>
 #include <EGL/egl.h>
-#include <GLES2/gl2.h>
-#include <GLES2/gl2ext.h>
+#include <GL/gl.h>
+#include <GL/glext.h>
+#include <GLES3/gl3.h>
+#include <GLES3/gl3ext.h>
 
 #include <fstream>
 #include <iostream>
   eglInitialize(display, nullptr, nullptr);
   eglBindAPI(EGL_OPENGL_ES_API);
 
-  const EGLint context_attribs[] = { EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE };
-  const EGLint config_attribs[] = { EGL_SURFACE_TYPE, EGL_DONT_CARE, EGL_RENDERABLE_TYPE,
-            EGL_OPENGL_ES2_BIT, EGL_NONE };
+  const EGLint config_attribs[] = {
+      EGL_SURFACE_TYPE, EGL_DONT_CARE,
+      EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+      EGL_NONE };
   EGLConfig egl_config;
   EGLint num_configs;
   if (!eglChooseConfig(display, config_attribs, &egl_config, 1, &num_configs)) {
     ERROR("Unable to choose EGL config");
   }
 
+  const EGLint context_attribs[] = { EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE };
   EGLContext context = eglCreateContext(display, egl_config, EGL_NO_CONTEXT, context_attribs);
   if (context == EGL_NO_CONTEXT) {
     ERROR("Failed to create GLES context");
   GLuint color_buffer;
   glGenRenderbuffers(1, &color_buffer);
   glBindRenderbuffer(GL_RENDERBUFFER, color_buffer);
-  glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8_OES, kWidth, kHeight);
+  glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8, kWidth, kHeight);
 
   GLuint depth_buffer;
   glGenRenderbuffers(1, &depth_buffer);
   return program;
 }
 
-void Draw(GLuint program) {
+uint32_t Draw(GLuint program) {
   glViewport(0, 0, kWidth, kHeight);
   glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glEnable(GL_DEPTH_TEST);
 
   glUseProgram(program);
+  GLuint query_object;
+  glGenQueries(1, &query_object);
+  glBeginQuery(GL_SAMPLES_PASSED, query_object);
+  if (glGetError()) {
+    ERROR("GLES version does not support GL_SAMPLES_PASSED");
+  }
   glDrawArrays(GL_TRIANGLES, 0, 6);
+  glEndQuery(GL_SAMPLES_PASSED);
+
+  uint32_t shaded_fragments = 0;
+  glGetQueryObjectuiv(query_object, GL_QUERY_RESULT, &shaded_fragments);
 
   glFinish();
+  return shaded_fragments;
 }
 
 GLubyte* ReadFramebuffer() {
   SetUpFramebuffer();
   GLuint program = CreateProgram();
   
-  Draw(program);
+  uint32_t shaded_fragments = Draw(program);
+  std::cout << "[Occlusion query] shaded fragments: " << shaded_fragments << std::endl;
 
   GLubyte* pixels = ReadFramebuffer();
   WriteImage(pixels);