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 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) {
+}
+
+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.";
+  }
+}
+
+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_);
+}
+
+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_) {

[Wez, 2012/09/25 20:29:29]

The monitoring code doesn't work if we don't have XFixes, since we'll never be
notified of selection changes.  How about we check for XFixes as the first thing
we do in Init(), and early-exit if it's not available - then we simply check
|clipboard_window_| in SetClipboard() and early-exit if it's not set, and we can
get rid of the |have_fixes_| bool.

, so why not check for XFixes first in Init() and if it's not present then 

[Lambros, 2012/09/25 22:42:39]

Done.

+    if (event->type == xfixes_event_base_ + XFixesSetSelectionOwnerNotify) {
+      XFixesSelectionNotifyEvent* notify_event =
+        reinterpret_cast<XFixesSelectionNotifyEvent*>(event);
+      OnSetSelectionOwnerNotify(notify_event->selection,
+                                notify_event->selection_timestamp);
+    }
+  }
+}
+
+void XServerClipboard::OnSetSelectionOwnerNotify(Atom selection,
+                                                 Time timestamp) {
+  // 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.

[Wez, 2012/09/25 20:29:29]

We agreed it makes more sense to cancel any pending request operations, and
ignore the resulting events, and dispatch new requests, if we see an event while
we're already processing one - do you intend to do that in a separate CL?

[Lambros, 2012/09/25 22:42:39]

Added TODO.

+  if (!get_selections_time_.is_null() &&
+      (base::TimeTicks::Now() - get_selections_time_) <
+      base::TimeDelta::FromSeconds(5)) {
+    return;
+  }
+
+  if (selection != clipboard_atom_ && selection != XA_PRIMARY) {

[Wez, 2012/09/25 20:29:29]

nit: Add comment "Only process PRIMARY and CLIPBOARD selections."

[Lambros, 2012/09/25 22:42:39]

Done.

+    return;
+  }
+
+  // If we own the selection, don't request details for it.
+  if (IsSelectionOwner(selection)) {
+    return;
+  }
+
+  get_selections_time_ = base::TimeTicks::Now();
+
+  // Before getting the value of the chosen selection, request the list of
+  // target formats it supports.
+  RequestSelectionTargets(selection);
+}
+
+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 -
+      // http://crbug.com/151447.
+      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_) {

[Wez, 2012/09/25 20:29:29]

nit: Add a comment to this block e.g. "Respond advertising XA_STRING,
UTF8_STRING and timestamp data for the selection."

[Lambros, 2012/09/25 22:42:39]

Done.

+      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];

[Wez, 2012/09/25 20:29:29]

nit: Comment "Respond with the timestamp of our selection; we always return
CurrentTime since our selections are set by remote clients, so there is no
associated local X event."

[Lambros, 2012/09/25 22:42:39]

Done.

+      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()) {

[Wez, 2012/09/25 20:29:29]

nit: Comment "Return the actual string data. We always return UTF8, regardless
of the configured locale."

[Lambros, 2012/09/25 22:42:39]

Done.

+        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,

[Wez, 2012/09/25 20:29:29]

nit: Shouldn't this be HandleSelectionNotify, since you're handling a
SelectionNotify event, not "doing" one?

[Lambros, 2012/09/25 22:42:39]

Done.

+                                         Atom type,
+                                         int format,
+                                         int item_count,
+                                         void* data) {
+  bool finished = false;
+
+  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) {
+    get_selections_time_ = base::TimeTicks();
+  }
+}
+
+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;
+  callback_.Run(kMimeTypeTextUtf8, data_);
+}
+
+bool XServerClipboard::IsSelectionOwner(Atom selection) {
+  return selections_owned_.find(selection) != selections_owned_.end();
+}
+
+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) {
+  // TODO(lambroslambrou): Should use a proper timestamp here instead of
+  // CurrentTime.  ICCCM recommends doing a zero-length property append, and
+  // getting a timestamp from the subsequent PropertyNotify event.
+  XSetSelectionOwner(display_, selection, clipboard_window_, CurrentTime);
+  if (XGetSelectionOwner(display_, selection) == clipboard_window_) {
+    selections_owned_.insert(selection);
+    selection_own_time_[selection] = CurrentTime;

[Wez, 2012/09/25 20:29:29]

This sets |selection_own_time_[selection]| to zero, so why bother keeping the
map?  Just return CurrentTime when responding to the timestamp request.

[Lambros, 2012/09/25 22:42:39]

Done, and moved TODO to where we actually use CurrentTime.

+  } else {
+    LOG(ERROR) << "XSetSelectionOwner failed for selection " << selection;
+  }
+}
+
+}  // namespace remoting