// 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_osmesa.h"

#include <GL/osmesa.h>

#include "base/logging.h"
#include "ui/gfx/geometry/size.h"
#include "ui/gl/gl_bindings.h"
#include "ui/gl/gl_surface.h"

namespace gl {

GLContextOSMesa::GLContextOSMesa(GLShareGroup* share_group)
    : GLContextReal(share_group),
      context_(nullptr),
      is_released_(false) {
}

bool GLContextOSMesa::Initialize(GLSurface* compatible_surface,
                                 const GLContextAttribs& attribs) {
  // webgl_compatibility_context and disabling bind_generates_resource are not
  // supported.
  DCHECK(!attribs.webgl_compatibility_context &&
         attribs.bind_generates_resource);

  DCHECK(!context_);

  OSMesaContext share_handle = static_cast<OSMesaContext>(
      share_group() ? share_group()->GetHandle() : nullptr);

  GLuint format = 0;
  switch (compatible_surface->GetFormat().GetPixelLayout()) {
    case GLSurfaceFormat::PIXEL_LAYOUT_BGRA:
      format = OSMESA_BGRA;
      break;
    case GLSurfaceFormat::PIXEL_LAYOUT_RGBA:
      format = OSMESA_RGBA;
      break;
    default:
      NOTREACHED();
      return false;
  }
  context_ = OSMesaCreateContextExt(format,
                                    0,  // depth bits
                                    0,  // stencil bits
                                    0,  // accum bits
                                    share_handle);
  if (!context_) {
    LOG(ERROR) << "OSMesaCreateContextExt failed.";
    return false;
  }

  return true;
}

void GLContextOSMesa::Destroy() {
  if (context_) {
    OSMesaDestroyContext(static_cast<OSMesaContext>(context_));
    context_ = nullptr;
  }
}

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

  gfx::Size size = surface->GetSize();

  ScopedReleaseCurrent release_current;
  if (!OSMesaMakeCurrent(context_,
                         surface->GetHandle(),
                         GL_UNSIGNED_BYTE,
                         size.width(),
                         size.height())) {
    LOG(ERROR) << "OSMesaMakeCurrent failed.";
    Destroy();
    return false;
  }
  // Track that we're no longer in a released state to workaround a mesa issue.
  is_released_ = false;

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

  // Row 0 is at the top.
  OSMesaPixelStore(OSMESA_Y_UP, 0);

  SetCurrent(surface);
  InitializeDynamicBindings();

  if (!surface->OnMakeCurrent(this)) {
    LOG(ERROR) << "Could not make current.";
    return false;
  }

  release_current.Cancel();
  return true;
}

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

  SetCurrent(nullptr);

  // Calling |OSMesaMakeCurrent| with nullptr here does not work to release the
  // context. As a workaround, keep track of the release state, so that we can
  // correctly determine the state of |IsCurrent|.
  is_released_ = true;
  OSMesaMakeCurrent(nullptr, nullptr, GL_UNSIGNED_BYTE, 0, 0);
}

bool GLContextOSMesa::IsCurrent(GLSurface* surface) {
  DCHECK(context_);

  // |OSMesaGetCurrentContext| doesn't correctly return nullptr when we release,
  // check the tracked |is_released_|. See |ReleaseCurrent|.
  bool native_context_is_current = !is_released_ &&
      context_ == OSMesaGetCurrentContext();

  // 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) {
    GLint width;
    GLint height;
    GLint format;
    void* buffer = nullptr;
    OSMesaGetColorBuffer(context_, &width, &height, &format, &buffer);
    if (buffer != surface->GetHandle())
      return false;
  }

  return true;
}

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

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

}  // namespace gl