ui/shell_dialogs/base_shell_dialog_win.h

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_SHELL_DIALOGS_BASE_SHELL_DIALOG_WIN_H_
#define UI_SHELL_DIALOGS_BASE_SHELL_DIALOG_WIN_H_

#include <shlobj.h>

#include <memory>
#include <set>

#include "base/memory/scoped_refptr.h"
#include "ui/shell_dialogs/base_shell_dialog.h"
#include "ui/shell_dialogs/shell_dialogs_export.h"

namespace base {
class SingleThreadTaskRunner;
}

namespace ui {

///////////////////////////////////////////////////////////////////////////////
// A base class for all shell dialog implementations that handles showing a
// shell dialog modally on its own thread.
class SHELL_DIALOGS_EXPORT BaseShellDialogImpl {
 public:
  BaseShellDialogImpl();

  BaseShellDialogImpl(const BaseShellDialogImpl&) = delete;
  BaseShellDialogImpl& operator=(const BaseShellDialogImpl&) = delete;

  virtual ~BaseShellDialogImpl();

  // Disables the window |owner|. Can be run from either the ui or the dialog
  // thread. This function is called on the dialog thread after the modal
  // Windows Common dialog functions return because Windows automatically
  // re-enables the owning window when those functions return, but we don't
  // actually want them to be re-enabled until the response of the dialog
  // propagates back to the UI thread, so we disable the owner manually after
  // the Common dialog function returns.
  static void DisableOwner(HWND owner);

 protected:
  // Represents a run of a dialog.
  class SHELL_DIALOGS_EXPORT RunState {
   public:
    RunState();

    RunState(const RunState&) = delete;
    RunState& operator=(const RunState&) = delete;

    ~RunState();

    // Owning HWND, may be null.
    HWND owner;

    // Dedicated sequence on which the dialog runs.
    scoped_refptr<base::SingleThreadTaskRunner> dialog_task_runner;
  };

  // Called at the beginning of a modal dialog run. Disables the owner window
  // and tracks it. Returns the dedicated single-threaded sequence that the
  // dialog will be run on.
  std::unique_ptr<RunState> BeginRun(HWND owner);

  // Cleans up after a dialog run. If the run_state has a valid HWND this makes
  // sure that the window is enabled. This is essential because BeginRun
  // aggressively guards against multiple modal dialogs per HWND. Must be called
  // on the UI thread after the result of the dialog has been determined.
  void EndRun(std::unique_ptr<RunState> run_state);

  // Returns true if a modal shell dialog is currently active for the specified
  // owner. Must be called on the UI thread.
  bool IsRunningDialogForOwner(HWND owner) const;

 private:
  typedef std::set<HWND> Owners;

  // A list of windows that currently own active shell dialogs for this
  // instance. For example, if the DownloadManager owns an instance of this
  // object and there are two browser windows open both with Save As dialog
  // boxes active, this list will consist of the two browser windows' HWNDs.
  // The derived class must call EndRun once the dialog is done showing to
  // remove the owning HWND from this list.
  // This object is static since it is maintained for all instances of this
  // object - i.e. you can't have two file pickers open for the
  // same owner, even though they might be represented by different instances
  // of this object.
  // This set only contains non-null HWNDs. NULL hwnds are not added to this
  // list.
  static Owners& GetOwners();
  static int instance_count_;
};

}  // namespace ui

#endif  // UI_SHELL_DIALOGS_BASE_SHELL_DIALOG_WIN_H_