// Copyright (c) 2012 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 "ui/gl/gl_context_cgl.h"

#include <OpenGL/CGLRenderers.h>
#include <OpenGL/CGLTypes.h>
#include <vector>

#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/trace_event/trace_event.h"
#include "ui/gl/gl_bindings.h"
#include "ui/gl/gl_implementation.h"
#include "ui/gl/gl_surface.h"
#include "ui/gl/gpu_switching_manager.h"

namespace gfx {

namespace {

bool g_support_renderer_switching;

struct CGLRendererInfoObjDeleter {
  void operator()(CGLRendererInfoObj* x) {
    if (x)
      CGLDestroyRendererInfo(*x);
  }
};

}  // namespace

static CGLPixelFormatObj GetPixelFormat() {
  static CGLPixelFormatObj format;
  if (format)
    return format;
  std::vector<CGLPixelFormatAttribute> attribs;
  // If the system supports dual gpus then allow offline renderers for every
  // context, so that they can all be in the same share group.
  if (ui::GpuSwitchingManager::GetInstance()->SupportsDualGpus()) {
    attribs.push_back(kCGLPFAAllowOfflineRenderers);
    g_support_renderer_switching = true;
  }
  if (GetGLImplementation() == kGLImplementationAppleGL) {
    attribs.push_back(kCGLPFARendererID);
    attribs.push_back((CGLPixelFormatAttribute) kCGLRendererGenericFloatID);
    g_support_renderer_switching = false;
  }
  if (GetGLImplementation() == kGLImplementationDesktopGLCoreProfile) {
    // These constants don't exist in the 10.6 SDK against which
    // Chromium currently compiles.
    const int kOpenGLProfile = 99;
    const int kOpenGL3_2Core = 0x3200;
    attribs.push_back(static_cast<CGLPixelFormatAttribute>(kOpenGLProfile));
    attribs.push_back(static_cast<CGLPixelFormatAttribute>(kOpenGL3_2Core));
  }

  attribs.push_back((CGLPixelFormatAttribute) 0);

  GLint num_virtual_screens;
  if (CGLChoosePixelFormat(&attribs.front(),
                           &format,
                           &num_virtual_screens) != kCGLNoError) {
    LOG(ERROR) << "Error choosing pixel format.";
    return nullptr;
  }
  if (!format) {
    LOG(ERROR) << "format == 0.";
    return nullptr;
  }
  DCHECK_NE(num_virtual_screens, 0);
  return format;
}

GLContextCGL::GLContextCGL(GLShareGroup* share_group)
  : GLContextReal(share_group),
    context_(nullptr),
    gpu_preference_(PreferIntegratedGpu),
    discrete_pixelformat_(nullptr),
    screen_(-1),
    renderer_id_(-1),
    safe_to_force_gpu_switch_(true) {
}

bool GLContextCGL::Initialize(GLSurface* compatible_surface,
                              GpuPreference gpu_preference) {
  DCHECK(compatible_surface);

  gpu_preference = ui::GpuSwitchingManager::GetInstance()->AdjustGpuPreference(
      gpu_preference);

  GLContextCGL* share_context = share_group() ?
      static_cast<GLContextCGL*>(share_group()->GetContext()) : nullptr;

  CGLPixelFormatObj format = GetPixelFormat();
  if (!format)
    return false;

  // If using the discrete gpu, create a pixel format requiring it before we
  // create the context.
  if (!ui::GpuSwitchingManager::GetInstance()->SupportsDualGpus() ||
      gpu_preference == PreferDiscreteGpu) {
    std::vector<CGLPixelFormatAttribute> discrete_attribs;
    discrete_attribs.push_back((CGLPixelFormatAttribute) 0);
    GLint num_pixel_formats;
    if (CGLChoosePixelFormat(&discrete_attribs.front(),
                             &discrete_pixelformat_,
                             &num_pixel_formats) != kCGLNoError) {
      LOG(ERROR) << "Error choosing pixel format.";
      return false;
    }
    // The renderer might be switched after this, so ignore the saved ID.
    share_group()->SetRendererID(-1);
  }

  CGLError res = CGLCreateContext(
      format,
      share_context ?
          static_cast<CGLContextObj>(share_context->GetHandle()) : nullptr,
      reinterpret_cast<CGLContextObj*>(&context_));
  if (res != kCGLNoError) {
    LOG(ERROR) << "Error creating context.";
    Destroy();
    return false;
  }

  gpu_preference_ = gpu_preference;
  // Contexts that prefer integrated gpu are known to use only the subset of GL
  // that can be safely migrated between the iGPU and the dGPU. Mark those
  // contexts as safe to forcibly transition between the GPUs by default.
  // http://crbug.com/180876, http://crbug.com/227228
  safe_to_force_gpu_switch_ = gpu_preference == PreferIntegratedGpu;
  return true;
}

void GLContextCGL::Destroy() {
  if (discrete_pixelformat_) {
    if (base::MessageLoop::current() != nullptr) {
      // Delay releasing the pixel format for 10 seconds to reduce the number of
      // unnecessary GPU switches.
      base::MessageLoop::current()->PostDelayedTask(
          FROM_HERE, base::Bind(&CGLReleasePixelFormat, discrete_pixelformat_),
          base::TimeDelta::FromSeconds(10));
    } else {
      CGLReleasePixelFormat(discrete_pixelformat_);
    }
    discrete_pixelformat_ = nullptr;
  }
  if (context_) {
    CGLDestroyContext(static_cast<CGLContextObj>(context_));
    context_ = nullptr;
  }
}

bool GLContextCGL::ForceGpuSwitchIfNeeded() {
  DCHECK(context_);

  // The call to CGLSetVirtualScreen can hang on some AMD drivers
  // http://crbug.com/227228
  if (safe_to_force_gpu_switch_) {
    int renderer_id = share_group()->GetRendererID();
    int screen;
    CGLGetVirtualScreen(static_cast<CGLContextObj>(context_), &screen);

    if (g_support_renderer_switching &&
        !discrete_pixelformat_ && renderer_id != -1 &&
        (screen != screen_ || renderer_id != renderer_id_)) {
      // Attempt to find a virtual screen that's using the requested renderer,
      // and switch the context to use that screen. Don't attempt to switch if
      // the context requires the discrete GPU.
      CGLPixelFormatObj format = GetPixelFormat();
      int virtual_screen_count;
      if (CGLDescribePixelFormat(format, 0, kCGLPFAVirtualScreenCount,
                                 &virtual_screen_count) != kCGLNoError)
        return false;

      for (int i = 0; i < virtual_screen_count; ++i) {
        int screen_renderer_id;
        if (CGLDescribePixelFormat(format, i, kCGLPFARendererID,
                                   &screen_renderer_id) != kCGLNoError)
          return false;

        screen_renderer_id &= kCGLRendererIDMatchingMask;
        if (screen_renderer_id == renderer_id) {
          CGLSetVirtualScreen(static_cast<CGLContextObj>(context_), i);
          screen_ = i;
          break;
        }
      }
      renderer_id_ = renderer_id;
    }
  }
  return true;
}

bool GLContextCGL::MakeCurrent(GLSurface* surface) {
  DCHECK(context_);

  if (!ForceGpuSwitchIfNeeded())
    return false;

  if (IsCurrent(surface))
    return true;

  ScopedReleaseCurrent release_current;
  TRACE_EVENT0("gpu", "GLContextCGL::MakeCurrent");

  if (CGLSetCurrentContext(
      static_cast<CGLContextObj>(context_)) != kCGLNoError) {
    LOG(ERROR) << "Unable to make gl context current.";
    return false;
  }

  // Set this as soon as the context is current, since we might call into GL.
  SetRealGLApi();

  SetCurrent(surface);
  if (!InitializeDynamicBindings()) {
    return false;
  }

  if (!surface->OnMakeCurrent(this)) {
    LOG(ERROR) << "Unable to make gl context current.";
    return false;
  }

  release_current.Cancel();
  return true;
}

void GLContextCGL::ReleaseCurrent(GLSurface* surface) {
  if (!IsCurrent(surface))
    return;

  SetCurrent(nullptr);
  CGLSetCurrentContext(nullptr);
}

bool GLContextCGL::IsCurrent(GLSurface* surface) {
  bool native_context_is_current = CGLGetCurrentContext() == context_;

  // If our context is current then our notion of which GLContext is
  // current must be correct. On the other hand, third-party code
  // using OpenGL might change the current context.
  DCHECK(!native_context_is_current || (GetRealCurrent() == this));

  if (!native_context_is_current)
    return false;

  return true;
}

void* GLContextCGL::GetHandle() {
  return context_;
}

void GLContextCGL::OnSetSwapInterval(int interval) {
  DCHECK(IsCurrent(nullptr));
}

void GLContextCGL::SetSafeToForceGpuSwitch() {
  safe_to_force_gpu_switch_ = true;
}


GLContextCGL::~GLContextCGL() {
  Destroy();
}

GpuPreference GLContextCGL::GetGpuPreference() {
  return gpu_preference_;
}

}  // namespace gfx