Implement clipboard for Chromoting Linux hosts.

remoting/host/linux/x_server_clipboard.cc

+// 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 "remoting/host/linux/x_server_clipboard.h"
+
+#include <X11/extensions/Xfixes.h>
+
+#include "base/callback.h"
+#include "base/logging.h"
+#include "remoting/base/constants.h"
+
+namespace {
+
+// Returns true if |a| is later than |b|, treating 0 as being a long time ago.
+// This is different from the usual meaning of CurrentTime (which is defined
+// to be 0).
+bool IsTimeLaterThan(Time a, Time b) {
+  if (a == 0) {
+    return false;
+  }
+  if (b == 0) {
+    return true;
+  }
+
+  // Deal with possible wrap-around: if |b| is close to the largest possible
+  // value, and |a| is close to 0, consider |a| to be later than |b| even
+  // though |a| is smaller numerically.

[Wez, 2012/09/20 23:37:46]

nit: Suggest: 32-bit X timestamps will wrap around after 49 days. Our comparison
assumes that we won't need to compare timestamps more than 24 days apart.

[Lambros, 2012/09/21 17:05:57]

Removed code.

+  return static_cast<long>(a - b) > 0;
+}
+
+}  // namespace
+
+namespace remoting {
+
+XServerClipboard::XServerClipboard()
+    : display_(NULL),
+      clipboard_window_(BadValue),
+      have_xfixes_(false),
+      xfixes_event_base_(-1),
+      xfixes_error_base_(-1),
+      clipboard_atom_(None),
+      large_selection_atom_(None),
+      selection_string_atom_(None),
+      targets_atom_(None),
+      timestamp_atom_(None),
+      utf8_string_atom_(None),
+      large_selection_property_(None),
+      current_selection_time_(0),
+      new_selection_(None),
+      getting_initial_selection_(true),
+      new_cut_text_(false),
+      had_valid_timestamp_(false) {
+}
+
+XServerClipboard::~XServerClipboard() {
+}
+
+void XServerClipboard::Init(Display* display,
+                            const ClipboardChangedCallback& callback) {
+  display_ = display;
+  callback_ = callback;
+
+  // If any of these X API calls fail, an X Error will be raised, crashing the
+  // process.  This is unlikely to occur in practice, and even if it does, it
+  // would mean the X server is in a bad state, so it's not worth trying to
+  // trap such errors here.
+
+  // TODO(lambroslambrou): Consider using ScopedXErrorHandler here, or consider
+  // placing responsibility for handling X Errors outside this class, since
+  // X Error handlers are global to all X connections.
+  clipboard_window_ = XCreateSimpleWindow(display_,
+                                          DefaultRootWindow(display_),
+                                          0, 0, 1, 1,  // x, y, width, height
+                                          0, 0, 0);
+
+  // TODO(lambroslambrou): Use ui::X11AtomCache for this, either by adding a
+  // dependency on ui/ or by moving X11AtomCache to base/.
+  const int kNumAtoms = 6;
+  const char* names[kNumAtoms] = {
+    "CLIPBOARD",
+    "INCR",
+    "SELECTION_STRING",
+    "TARGETS",
+    "TIMESTAMP",
+    "UTF8_STRING" };
+  Atom atoms[kNumAtoms];
+  if (XInternAtoms(display_, const_cast<char**>(names), kNumAtoms, False,
+                   atoms)) {
+    clipboard_atom_ = atoms[0];
+    large_selection_atom_ = atoms[1];
+    selection_string_atom_ = atoms[2];
+    targets_atom_ = atoms[3];
+    timestamp_atom_ = atoms[4];
+    utf8_string_atom_ = atoms[5];
+  } else {
+    LOG(ERROR) << "XInternAtoms failed";
+  }
+
+  if (XFixesQueryExtension(display_, &xfixes_event_base_,
+                           &xfixes_error_base_)) {
+    have_xfixes_ = true;
+    XFixesSelectSelectionInput(display_, clipboard_window_, XA_PRIMARY,
+                               XFixesSetSelectionOwnerNotifyMask);
+    XFixesSelectSelectionInput(display_, clipboard_window_, clipboard_atom_,
+                               XFixesSetSelectionOwnerNotifyMask);
+  } else {
+    LOG(INFO) << "X server does not support XFixes.";
+  }
+
+  GetSelections(None, 0);
+}
+
+void XServerClipboard::SetClipboard(const std::string& mime_type,
+                                    const std::string& data) {
+  DCHECK(display_);
+
+  // Currently only UTF-8 is supported.
+  if (mime_type != kMimeTypeTextUtf8) {
+    return;
+  }
+
+  data_ = data;
+
+  AssertSelectionOwnership(XA_PRIMARY);
+  AssertSelectionOwnership(clipboard_atom_);
+  current_selection_time_ = CurrentTime;
+}
+
+void XServerClipboard::ProcessXEvent(XEvent* event) {
+  if (event->xany.window != clipboard_window_) {
+    return;
+  }
+
+  switch (event->type) {
+    case PropertyNotify:
+      OnPropertyNotify(event);
+      break;
+    case SelectionNotify:
+      OnSelectionNotify(event);
+      break;
+    case SelectionRequest:
+      OnSelectionRequest(event);
+      break;
+    default:
+      break;
+  }
+
+  if (have_xfixes_) {
+    if (event->type == xfixes_event_base_ + XFixesSetSelectionOwnerNotify) {
+      XFixesSelectionNotifyEvent* notify_event =
+        reinterpret_cast<XFixesSelectionNotifyEvent*>(event);
+      GetSelections(notify_event->selection, notify_event->selection_timestamp);
+    }
+  }
+}
+
+void XServerClipboard::GetSelections(Atom selection, Time timestamp) {
+  // This is called to check the state of the X selections.  It is called
+  // during initialization (with |selection| and |timestamp| equal to zero),

[Wez, 2012/09/20 23:37:46]

If it's called during initialization with |selection| set to zero, why not set
|selection| to XA_PRIMARY in the initialization call, and avoid the |selection
!= None| test below?

[Lambros, 2012/09/21 17:05:57]

No loner called during init.  This is now just an event-handler, so I've renamed
as you suggested.

+  // and whenever XFixesSelectionNotifyEvent is received (with |selection| and
+  // |timestamp| taken from the notification event).  This requests information
+  // from the selection owner(s) about the timestamp, the target list and the
+  // string value of the selection.
+
+  // We start out trying to establish the timestamp(s) on the selections to
+  // decide which one to retrieve.  If |selection| and |timestamp| are non-zero
+  // then we retrieve that selection.  Otherwise we request the timestamp(s)
+  // from the selection owner.  If we get a valid timestamp and one of the
+  // selections is newer than |current_selection_time_|, then we use that

[Wez, 2012/09/20 23:37:46]

nit for discussion off-CL: Do we really need these timestamp comparisons? Are
there circumstances under which we can we see these notifications out-of-order?

[Lambros, 2012/09/21 17:05:57]

Done.  PTAL at the simplified version.

+  // selection.
+
+  // Protect against receiving new XFixes selection notifications whilst we're
+  // in the middle of waiting for information from the current selection owner.
+  // A reasonable timeout allows for misbehaving apps that don't respond
+  // quickly to our requests.
+  if (!get_selections_time_.is_null() &&
+      (base::TimeTicks::Now() - get_selections_time_) <
+      base::TimeDelta::FromSeconds(5)) {
+    return;
+  }
+
+  if (selection != None) {
+    if (selection != clipboard_atom_ && selection != XA_PRIMARY) {
+      return;
+    }
+  } else {
+    selection = XA_PRIMARY;
+  }
+
+  // If the selection is actually owned by us, there's no need to request the
+  // details for it.

[Wez, 2012/09/20 23:37:46]

nit: Suggest:
If we own the selection, don't request details for it.

[Lambros, 2012/09/21 17:05:57]

Done.

+  if (IsSelectionOwner(selection)) {
+    FinishGetSelections();
+  }
+
+  get_selections_time_ = base::TimeTicks::Now();
+
+  if (timestamp) {
+    current_selection_time_ = timestamp;
+
+    // Before getting the value of the chosen selection, request the list of
+    // targets supported for that selection (currently only UTF8_STRING and

[Wez, 2012/09/20 23:37:46]

nit: ... the list of target formats it supports.

[Lambros, 2012/09/21 17:05:57]

Done.

+    // STRING are supported).

[Wez, 2012/09/20 23:37:46]

nit: No need to clarify the targets we support here.

[Lambros, 2012/09/21 17:05:57]

Done.

+    RequestSelectionTargets(selection);
+  } else {
+    new_selection_ = 0;
+    had_valid_timestamp_ = false;
+    RequestSelectionTimestamp(selection, CurrentTime);
+  }
+}
+
+void XServerClipboard::FinishGetSelections() {
+  getting_initial_selection_ = false;
+  get_selections_time_ = base::TimeTicks();
+}
+
+void XServerClipboard::OnPropertyNotify(XEvent* event) {
+  if (large_selection_property_ != None &&
+      event->xproperty.atom == large_selection_property_ &&
+      event->xproperty.state == PropertyNewValue) {
+    Atom type;
+    int format;
+    unsigned long item_count, after;
+    unsigned char *data;
+    XGetWindowProperty(display_, clipboard_window_, large_selection_property_,
+                       0, ~0L, True, AnyPropertyType, &type, &format,
+                       &item_count, &after, &data);
+    if (type != None) {
+      // TODO(lambroslambrou): Properly support large transfers.

[Wez, 2012/09/20 23:37:46]

nit: Add a bug for that and refer to it here.

[Lambros, 2012/09/21 17:05:57]

Done.

+      XFree(data);
+
+      // If the property is zero-length then the large transfer is complete.
+      if (item_count == 0) {
+        large_selection_property_ = None;
+      }
+    }
+  }
+}
+
+void XServerClipboard::OnSelectionNotify(XEvent* event) {
+  if (event->xselection.property != None) {
+    Atom type;
+    int format;
+    unsigned long item_count, after;
+    unsigned char *data;
+    XGetWindowProperty(display_, clipboard_window_,
+                       event->xselection.property, 0, ~0L, True,
+                       AnyPropertyType, &type, &format,
+                       &item_count, &after, &data);
+    if (type == large_selection_atom_) {
+      // Large selection - just read and ignore these for now.
+      large_selection_property_ = event->xselection.property;
+    } else {
+      // Standard selection - call the selection notifier.
+      large_selection_property_ = None;
+      if (type != None) {
+        DoSelectionNotify(&event->xselection, type, format, item_count, data);
+        XFree(data);
+        return;
+      }
+    }
+  }
+  DoSelectionNotify(&event->xselection, 0, 0, 0, 0);
+}
+
+void XServerClipboard::OnSelectionRequest(XEvent* event) {
+  XSelectionEvent selection_event;
+  selection_event.type = SelectionNotify;
+  selection_event.display = event->xselectionrequest.display;
+  selection_event.requestor = event->xselectionrequest.requestor;
+  selection_event.selection = event->xselectionrequest.selection;
+  selection_event.time = event->xselectionrequest.time;
+  selection_event.target = event->xselectionrequest.target;
+  if (event->xselectionrequest.property == None) {
+    event->xselectionrequest.property = event->xselectionrequest.target;
+  }
+  if (!IsSelectionOwner(selection_event.selection)) {
+    selection_event.property = None;
+  } else {
+    selection_event.property = event->xselectionrequest.property;
+    if (selection_event.target == targets_atom_) {
+      Atom targets[3];
+      targets[0] = timestamp_atom_;
+      targets[1] = utf8_string_atom_;
+      targets[2] = XA_STRING;
+      XChangeProperty(display_, selection_event.requestor,
+                      selection_event.property, XA_ATOM, 32, PropModeReplace,
+                      reinterpret_cast<unsigned char*>(targets), 3);
+    } else if (selection_event.target == timestamp_atom_) {
+      Time time = selection_own_time_[selection_event.selection];
+      XChangeProperty(display_, selection_event.requestor,
+                      selection_event.property, XA_INTEGER, 32,
+                      PropModeReplace, reinterpret_cast<unsigned char*>(&time),
+                      1);
+    } else if (selection_event.target == utf8_string_atom_ ||
+               selection_event.target == XA_STRING) {
+      if (!data_.empty()) {
+        XChangeProperty(display_, selection_event.requestor,
+                        selection_event.property, selection_event.target, 8,
+                        PropModeReplace,
+                        reinterpret_cast<unsigned char*>(
+                            const_cast<char*>(data_.data())),
+                        data_.size());
+      }
+    }
+  }
+  XSendEvent(display_, selection_event.requestor, False, 0,
+             reinterpret_cast<XEvent*>(&selection_event));
+}
+
+void XServerClipboard::DoSelectionNotify(XSelectionEvent* event,
+                                         Atom type,
+                                         int format,
+                                         int item_count,
+                                         void* data) {
+  bool finished = false;
+
+  if (event->target == timestamp_atom_) {
+    finished = HandleSelectionTimestampEvent(event, format, item_count, data);
+  } else if (event->target == targets_atom_) {
+    finished = HandleSelectionTargetsEvent(event, format, item_count, data);
+  } else if (event->target == utf8_string_atom_ ||
+             event->target == XA_STRING) {
+    finished = HandleSelectionStringEvent(event, format, item_count, data);
+  }
+
+  if (finished) {
+    FinishGetSelections();
+  }
+}
+
+bool XServerClipboard::HandleSelectionTimestampEvent(XSelectionEvent* event,
+                                                     int format,
+                                                     int item_count,
+                                                     void* data) {
+  if (event->property == timestamp_atom_) {
+    // The selection owner properly responded to the timestamp request.  Test
+    // the timestamp for validity.
+    if (data && format == 32 && item_count == 1) {
+      Time selection_time = *static_cast<Time*>(data);
+      if (selection_time != 0) {
+        had_valid_timestamp_ = true;
+      }
+      if (IsTimeLaterThan(selection_time, current_selection_time_)) {
+        current_selection_time_ = selection_time;
+        new_selection_ = event->selection;
+      }
+    }
+  }
+
+  if (event->selection == XA_PRIMARY) {
+    if (!IsSelectionOwner(clipboard_atom_)) {
+      RequestSelectionTimestamp(clipboard_atom_, event->time);
+      return false;
+    }
+  } else if (event->selection != clipboard_atom_) {
+    return false;
+  }
+
+  if (getting_initial_selection_ && had_valid_timestamp_) {
+    return true;
+  }
+
+  if (new_selection_) {
+    RequestSelectionTargets(new_selection_);
+  } else if (!had_valid_timestamp_) {
+    // If we didn't get a valid timestamp (for example an app like Mozilla
+    // which sets a zero timestamp, or an app like VMWare which doesn't support
+    // the timestamp target), we can't use the timestamp optimisation so we
+    // have to get the actual value of the selection each time.

[Wez, 2012/09/20 23:37:46]

But this will only be triggered by an XFixes notification?

[Lambros, 2012/09/21 17:05:57]

Removed code.  We no longer request the timestamp of the selection, so we no
longer expect to get a timestamp response.

+    RequestSelectionTargets(XA_PRIMARY);
+  } else {
+    return true;
+  }
+  return false;
+}
+
+bool XServerClipboard::HandleSelectionTargetsEvent(XSelectionEvent* event,
+                                                   int format,
+                                                   int item_count,
+                                                   void* data) {
+  if (event->property == targets_atom_) {
+    if (data && format == 32) {
+      // The XGetWindowProperty man-page specifies that the returned
+      // property data will be an array of |long|s in the case where
+      // |format| == 32.  Although the items are 32-bit values (as stored and
+      // sent over the X protocol), Xlib presents the data to the client as an
+      // array of |long|s, with zero-padding on a 64-bit system where |long|
+      // is bigger than 32 bits.
+      const long* targets = static_cast<const long*>(data);
+      for (int i = 0; i < item_count; i++) {
+        if (targets[i] == static_cast<long>(utf8_string_atom_)) {
+          RequestSelectionString(event->selection, utf8_string_atom_);
+          return false;
+        }
+      }
+    }
+  }
+  RequestSelectionString(event->selection, XA_STRING);
+  return false;
+}
+
+bool XServerClipboard::HandleSelectionStringEvent(XSelectionEvent* event,
+                                          int format,
+                                          int item_count,
+                                          void* data) {
+  if (event->property != selection_string_atom_ || !data || format != 8) {
+    return true;
+  }
+
+  std::string text(static_cast<char*>(data), item_count);
+
+  if (event->target == XA_STRING || event->target == utf8_string_atom_) {
+    NotifyClipboardText(text);
+  }
+  return true;
+}
+
+void XServerClipboard::NotifyClipboardText(const std::string& text) {
+  data_ = text;
+  new_cut_text_ = false;
+  if (!getting_initial_selection_) {
+    callback_.Run(kMimeTypeTextUtf8, data_);
+  }
+}
+
+bool XServerClipboard::IsSelectionOwner(Atom selection) {
+  return selections_owned_.find(selection) != selections_owned_.end();
+}
+
+void XServerClipboard::RequestSelectionTimestamp(Atom selection, Time time) {
+  XConvertSelection(display_, selection, timestamp_atom_, timestamp_atom_,
+                    clipboard_window_, time);
+}
+
+void XServerClipboard::RequestSelectionTargets(Atom selection) {
+  XConvertSelection(display_, selection, targets_atom_, targets_atom_,
+                    clipboard_window_, CurrentTime);
+}
+
+void XServerClipboard::RequestSelectionString(Atom selection, Atom target) {
+  XConvertSelection(display_, selection, target, selection_string_atom_,
+                    clipboard_window_, CurrentTime);
+}
+
+void XServerClipboard::AssertSelectionOwnership(Atom selection) {
+  XSetSelectionOwner(display_, selection, clipboard_window_, CurrentTime);
+  if (XGetSelectionOwner(display_, selection) == clipboard_window_) {
+    selections_owned_.insert(selection);
+    selection_own_time_[selection] = CurrentTime;
+  } else {
+    LOG(ERROR) << "XSetSelectionOwner failed for selection " << selection;
+  }
+}
+
+}  // namespace remoting