ui/base/x/selection_requestor.h

// Copyright (c) 2013 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.

#ifndef UI_BASE_X_SELECTION_REQUESTOR_H_
#define UI_BASE_X_SELECTION_REQUESTOR_H_

#include <X11/Xlib.h>

// Get rid of a macro from Xlib.h that conflicts with Aura's RootWindow class.
#undef RootWindow

#include <vector>

#include "base/basictypes.h"
#include "base/callback.h"
#include "base/memory/ref_counted_memory.h"
#include "ui/base/ui_export.h"
#include "ui/gfx/x/x11_atom_cache.h"

namespace ui {
class SelectionData;

// Requests and later receives data from the X11 server through the selection
// system.
//
// X11 uses a system called "selections" to implement clipboards and drag and
// drop. This class interprets messages from the statefull selection request
// API. SelectionRequestor should only deal with the X11 details; it does not
// implement per-component fast-paths.
class UI_EXPORT SelectionRequestor {
 public:
  SelectionRequestor(Display* xdisplay,
                     ::Window xwindow,
                     ::Atom selection_name);
  ~SelectionRequestor();

  // Does the work of requesting |target| from the selection we handle,
  // spinning up the nested message loop, and reading the resulting data
  // back. |out_data| is allocated with the X allocator and must be freed with
  // XFree(). |out_data_bytes| is the length in machine chars, while
  // |out_data_items| is the length in |out_type| items.
  bool PerformBlockingConvertSelection(
      ::Atom target,
      scoped_refptr<base::RefCountedMemory>* out_data,
      size_t* out_data_bytes,
      size_t* out_data_items,
      ::Atom* out_type);

  // Returns the first of |types| offered by the current selection holder, or
  // returns NULL if none of those types are available.
  SelectionData RequestAndWaitForTypes(const std::vector< ::Atom>& types);

  // It is our owner's responsibility to plumb X11 SelectionNotify events on
  // |xwindow_| to us.
  void OnSelectionNotify(const XSelectionEvent& event);

 private:
  // Our X11 state.
  Display* x_display_;
  ::Window x_window_;

  // True if we're currently running a nested message loop, waiting for data to
  // come back from the X server.
  bool in_nested_loop_;

  // The X11 selection that this instance communicates on.
  ::Atom selection_name_;

  // Data to the current XConvertSelection request. Used for error detection;
  // we verify it on the return message.
  ::Atom current_target_;

  // The property in the returning SelectNotify message is used to signal
  // success. If None, our request failed somehow. If equal to the property
  // atom that we sent in the XConvertSelection call, we can read that property
  // on |x_window_| for the requested data.
  ::Atom returned_property_;

  // Called to terminate the nested message loop.
  base::Closure quit_closure_;

  X11AtomCache atom_cache_;

  DISALLOW_COPY_AND_ASSIGN(SelectionRequestor);
};

}  // namespace ui

#endif  // UI_BASE_X_SELECTION_REQUESTOR_H_