// 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.

// This file implements the GLContextWGL and PbufferGLContext classes.

#include "ui/gl/gl_context_wgl.h"

#include "base/debug/trace_event.h"
#include "base/logging.h"
#include "ui/gl/gl_bindings.h"
#include "ui/gl/gl_implementation.h"
#include "ui/gl/gl_surface_wgl.h"

namespace gfx {

GLContextWGL::GLContextWGL(GLShareGroup* share_group)
    : GLContextReal(share_group),
      context_(NULL) {
}

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

std::string GLContextWGL::GetExtensions() {
  const char* extensions = NULL;
  if (g_driver_wgl.fn.wglGetExtensionsStringARBFn)
    extensions = wglGetExtensionsStringARB(GLSurfaceWGL::GetDisplayDC());
  else if (g_driver_wgl.fn.wglGetExtensionsStringEXTFn)
    extensions = wglGetExtensionsStringEXT();

  if (extensions)
    return GLContext::GetExtensions() + " " + extensions;

  return GLContext::GetExtensions();
}

bool GLContextWGL::Initialize(
    GLSurface* compatible_surface, GpuPreference gpu_preference) {
  // Get the handle of another initialized context in the share group _before_
  // setting context_. Otherwise this context will be considered initialized
  // and could potentially be returned by GetHandle.
  HGLRC share_handle = static_cast<HGLRC>(share_group()->GetHandle());

  context_ = wglCreateContext(
      static_cast<HDC>(compatible_surface->GetHandle()));
  if (!context_) {
    LOG(ERROR) << "Failed to create GL context.";
    Destroy();
    return false;
  }

  if (share_handle) {
    if (!wglShareLists(share_handle, context_)) {
      LOG(ERROR) << "Could not share GL contexts.";
      Destroy();
      return false;
    }
  }

  return true;
}

void GLContextWGL::Destroy() {
  if (context_) {
    wglDeleteContext(context_);
    context_ = NULL;
  }
}

bool GLContextWGL::MakeCurrent(GLSurface* surface) {
  DCHECK(context_);
  if (IsCurrent(surface))
    return true;

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

  if (!wglMakeCurrent(static_cast<HDC>(surface->GetHandle()), context_)) {
    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) << "Could not make current.";
    return false;
  }

  release_current.Cancel();
  return true;
}

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

  SetCurrent(NULL);
  wglMakeCurrent(NULL, NULL);
}

bool GLContextWGL::IsCurrent(GLSurface* surface) {
  bool native_context_is_current =
      wglGetCurrentContext() == 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;

  if (surface) {
    if (wglGetCurrentDC() != surface->GetHandle())
      return false;
  }

  return true;
}

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

void GLContextWGL::SetSwapInterval(int interval) {
  DCHECK(IsCurrent(NULL));
  if (gfx::g_driver_wgl.ext.b_WGL_EXT_swap_control) {
    wglSwapIntervalEXT(interval);
  } else {
      LOG(WARNING) <<
          "Could not disable vsync: driver does not "
          "support WGL_EXT_swap_control";
  }
}

}  // namespace gfx