ui/gl/child_window_win.cc

// Copyright 2017 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/child_window_win.h"

#include <memory>

#include "base/bind.h"
#include "base/compiler_specific.h"
#include "base/debug/alias.h"
#include "base/memory/weak_ptr.h"
#include "base/message_loop/message_pump_type.h"
#include "base/win/wrapped_window_proc.h"
#include "ui/gfx/win/hwnd_util.h"
#include "ui/gfx/win/window_impl.h"

namespace gl {

namespace {

ATOM g_window_class;

// This runs on the window owner thread.
void InitializeWindowClass() {
  if (g_window_class)
    return;

  WNDCLASSEX intermediate_class;
  base::win::InitializeWindowClass(
      L"Intermediate D3D Window",
      &base::win::WrappedWindowProc<::DefWindowProc>, CS_OWNDC, 0, 0, nullptr,
      reinterpret_cast<HBRUSH>(GetStockObject(BLACK_BRUSH)), nullptr, nullptr,
      nullptr, &intermediate_class);
  g_window_class = RegisterClassEx(&intermediate_class);
  if (!g_window_class) {
    LOG(ERROR) << "RegisterClass failed.";
    return;
  }
}

// Hidden popup window  used as a parent for the child surface window.
// Must be created and destroyed on the thread.
class HiddenPopupWindow : public gfx::WindowImpl {
 public:
  static HWND Create() {
    gfx::WindowImpl* window = new HiddenPopupWindow;

    window->set_window_style(WS_POPUP);
    window->set_window_ex_style(WS_EX_TOOLWINDOW);
    window->Init(GetDesktopWindow(), gfx::Rect());
    EnableWindow(window->hwnd(), FALSE);
    // The |window| instance is now owned by the window user data.
    DCHECK_EQ(window, gfx::GetWindowUserData(window->hwnd()));
    return window->hwnd();
  }

  static void Destroy(HWND window) {
    // This uses the fact that the window user data contains a pointer
    // to gfx::WindowImpl instance.
    gfx::WindowImpl* window_data =
        reinterpret_cast<gfx::WindowImpl*>(gfx::GetWindowUserData(window));
    DCHECK_EQ(window, window_data->hwnd());
    DestroyWindow(window);
    delete window_data;
  }

 private:
  // Explicitly do nothing in Close. We do this as some external apps may get a
  // handle to this window and attempt to close it.
  void OnClose() {}

  CR_BEGIN_MSG_MAP_EX(HiddenPopupWindow)
    CR_MSG_WM_CLOSE(OnClose)
  CR_END_MSG_MAP()

  CR_MSG_MAP_CLASS_DECLARATIONS(HiddenPopupWindow)
};

// This runs on the window owner thread.
void CreateWindowsOnThread(const gfx::Size& size,
                           base::WaitableEvent* event,
                           HWND* child_window,
                           HWND* parent_window) {
  InitializeWindowClass();
  DCHECK(g_window_class);

  // Create hidden parent window on the current thread.
  *parent_window = HiddenPopupWindow::Create();
  // Create child window.
  // WS_EX_NOPARENTNOTIFY and WS_EX_LAYERED make the window transparent for
  // input. WS_EX_NOREDIRECTIONBITMAP avoids allocating a
  // bitmap that would otherwise be allocated with WS_EX_LAYERED, the bitmap is
  // only necessary if using Gdi objects with the window.
  HWND window = CreateWindowEx(
      WS_EX_NOPARENTNOTIFY | WS_EX_LAYERED | WS_EX_TRANSPARENT |
          WS_EX_NOREDIRECTIONBITMAP,
      reinterpret_cast<wchar_t*>(g_window_class), L"",
      WS_CHILDWINDOW | WS_DISABLED | WS_VISIBLE, 0, 0, size.width(),
      size.height(), *parent_window, nullptr, nullptr, nullptr);
  if (!window) {
    logging::SystemErrorCode error = logging::GetLastSystemErrorCode();
    base::debug::Alias(&error);
    CHECK(false);
  }
  *child_window = window;
  event->Signal();
}

// This runs on the main thread after the window was destroyed on window owner
// thread.
void DestroyThread(std::unique_ptr<base::Thread> thread) {
  thread->Stop();
}

// This runs on the window owner thread.
void DestroyWindowsOnThread(HWND child_window, HWND hidden_popup_window) {
  DestroyWindow(child_window);
  HiddenPopupWindow::Destroy(hidden_popup_window);
}

}  // namespace

ChildWindowWin::ChildWindowWin(HWND parent_window)
    : parent_window_(parent_window) {}

void ChildWindowWin::Initialize() {
  if (window_)
    return;

  thread_ = std::make_unique<base::Thread>("Window owner thread");
  base::Thread::Options options(base::MessagePumpType::UI, 0);
  thread_->StartWithOptions(options);

  base::WaitableEvent event(base::WaitableEvent::ResetPolicy::AUTOMATIC,
                            base::WaitableEvent::InitialState::NOT_SIGNALED);

  RECT window_rect;
  GetClientRect(parent_window_, &window_rect);

  thread_->task_runner()->PostTask(
      FROM_HERE,
      base::BindOnce(&CreateWindowsOnThread, gfx::Rect(window_rect).size(),
                     &event, &window_, &initial_parent_window_));
  event.Wait();
}

ChildWindowWin::~ChildWindowWin() {
  if (thread_) {
    scoped_refptr<base::TaskRunner> task_runner = thread_->task_runner();
    task_runner->PostTaskAndReply(
        FROM_HERE,
        base::BindOnce(&DestroyWindowsOnThread, window_,
                       initial_parent_window_),
        base::BindOnce(&DestroyThread, std::move(thread_)));
  }
}

scoped_refptr<base::TaskRunner> ChildWindowWin::GetTaskRunnerForTesting() {
  DCHECK(thread_);
  return thread_->task_runner();
}

}  // namespace gl