WIP: X clipboard stuff

chrome/browser/gtk/xclipboard.cc

+// Have the ICCCM in hand when reading this code:
+// http://tronche.com/gui/x/icccm/sec-2.html#s-2
+
+struct InflightDownRequest {
+  Window requestor;  // requesting window
+  Atom selection;  // clipboard requested
+  Atom target;  // type of the data requested
+  Atom property;  // target property name on |requestor|
+  Time time;  // request timestamp
+};
+
+struct ReplyReorderBufferKey {
+  Window requestor;
+  Atom selection;
+  Atom target;
+  Time time;
+
+  ReplyReorderBufferKey(const InflightDownRequest& downreq)
+      : requestor(downreq.requestor),
+        selection(downreq.selection),
+        target(downreq.target),
+        time(downreq.time) {
+  }
+
+  bool operator==(const ReplyReorderBufferKey& other) {
+    return other.requestor == requestor &&
+           other.selection == selection &&
+           other.target == target &&
+           other.time == time;
+  }
+};
+
+struct PendingReply {
+  explicit PendingReply(const InflightDownRequest& in_downreq)
+      : downreq(in_downreq),
+        data(NULL),
+        length(0) {
+  }
+
+  PendingReply(const InflightDownRequest& in_downreq, const uint8_t* data,
+               size_t in_length)
+      : downreq(in_downreq),
+        data(in_data),
+        length(in_length) {
+  }
+
+  InflightDownRequest downreq;
+  const uint8_t* data;  // if NULL for |ReplyWithFailure|
+  size_t length;
+};
+
+struct XClipboardImpl {
+  Display* display;
+  Window window;
+  uint64_t current_tag;
+
+  std::map<uint64_t, InflightUpRequest> up_requests;
+  std::map<uint64_t, InflightDownRequest> down_requests;
+
+  // ICCCM says: "If the owner receives more than one SelectionRequest event
+  // with the same requestor, selection, target, and timestamp, it must respond
+  // to them in the same order in which they were received."
+  //
+  // Thus, we may need to reorder the replies when we are sending. We have a
+  // map from |ReplyReorderBufferKey| to a list of uint64_t tags. This list is
+  // the received order and we check that we don't transmit a reply
+  // out-of-order. If we do, we stick the reply in the reorder buffer and it'll
+  // get sent when its predecessor is sent.
+  std::map<ReplyReorderBufferKey, std::deque<uint64_t> > reply_order_map_;
+  std::map<uint64_t, PendingReply> pending_replies_;
+
+  // Some replies to other X clients will take multiple round trips (because of
+  // the size of the data). Sometimes we'll get an async X error from the X
+  // server if it's out of memory. For these reasons, we need to keep track of
+  // the curently uploading replies. This map is indexed by X serial number.
+  std::map<unsigned long, InflightReply> inflight_replies_;
+};
+
+XClipboard::XClipboard(void* display, Delegate* delegate)
+    : delegate_(delegate_),
+      pimpl_(new XClipboardImpl) {
+  const Window root_window = XDefaultRootWindow(display);
+  const int default_screen = XDefaultScreen(display);
+  Visual *const default_visual = XDefaultVisual(display, default_screen);
+
+  pimpl_->current_tag = 0;
+  pimpl_->display = reinterpret_cast<Display*>(display);
+
+  pimpl_->window = XCreateWindow(
+      display, root_window, 0, 0 /* x, y */, 1, 1 /* width, height */,
+      0 /* border width */, 0 /* depth */, InputOnly, default_visual,
+      0 /* value mask */, NULL /* values */);
+  CHECK(pimpl_->window);
+
+  XSelectInput(display, pimpl_->window, PropertyChangeMask);
+}
+
+XClipboard::~XClipboard() {
+  if (pimpl_->up_requests.size() ||
+      pimpl_->down_requests.size()) {
+    LOG(ERROR) << "XClipboard deleted with outstanding requests.";
+  }
+
+  delete pimpl_;
+}
+
+static Atom TypeToAtom(Display* display, XClipboard::Type clipboard_type) {
+  switch(clipboard_type) {
+    case CLIPBOARD_PRIMARY:
+      return XA_PRIMARY;
+    case CLIPBOARD_SECONDARY:
+      return XA_SECONDARY;
+    case CLIPBOARD_CLIPBOARD:
+      return XInternAtom(display, "CLIPBOARD");
+    default:
+      CHECK(false) << "Unknown clipboard type: " << clipboard_type;
+  }
+}
+
+bool XClipboard::AssertOwnership(Type clipboard_type) {
+  const Atom clipboard_atom = TypeToAtom(pimpl_->display, clipboard_type);
+  XSetSelectionOwner(pimpl_->display, clipboard_atom, pimpl_->window,
+                     CurrentAtom);
+  if (XGetSelectionOwner(pimpl_->display, clipboard_atom) != pimpl_->window)
+    return false;
+
+  return true;
+}
+
+static void SendReplyWithFailure(Display* dpy,
+                                 const InflightDownRequest& req) {
+  XEvent reply;
+  reply.xselection.type = SelectionNotify;
+  reply.xselection.display = dpy;
+  reply.xselection.requestor = req.requestor;
+  reply.xselection.selection = req.selection;
+  reply.xselection.target = req.target;
+  reply.xselection.time = req.time;
+  reply.xselection.property = None;
+  XSendEvent(dpy, req.requestor, 0 /* propagate */, 0 /* event mask */, &reply);
+}
+
+static void SendReplyWithContents(Display* dpy,
+                                  const InflightDownRequest& req,
+                                  const uint8_t* data, size_t length) {
+  // XMaxRequestSize returns the maximum request size in 4-byte words.
+  const size_t max_request_size = XMaxRequestSize(dpy);
+  // No matter what the X server requests, we won't transfer in chunks larger
+  // than this.
+  static const size_t kMaxUploadSize = 1 * 1024 * 1024;
+
+  // If either of the two bits are set, we'll overflow when shifting.
+  if (max_request_size >> (sizeof(max_request_size) * 8) - 2) {
+    max_request_size = LONG_MAX;
+  } else {
+    max_request_size <<= 2;
+  }
+
+  if (max_request_size > kMaxUploadSize)
+    max_request_size = kMaxUploadSize;
+
+  if (length < kMaxUploadSize) {
+    // We'll try to do the whole thing in one go
+    XChangeProperty(dpy, req.requestor, req.property, req.target,
+                    8 /* 8-bit words */, PropModeReplace,
+                    data, length);
+
+    // At this point we need to wait to either get an event that the property
+    // was set, or an error. Since the errors are async, we need to get the
+    // next serial number (before calling XChangeProperty) with
+    // |XNextRequest(dpy)| and, in the error handler, fallback to INCR with
+    // smaller chunks (maybe).
+  } else {
+    // INCR protocol
+  }
+
+  XEvent reply;
+  reply.xselection.type = SelectionNotify;
+  reply.xselection.display = dpy;
+  reply.xselection.requestor = req.requestor;
+  reply.xselection.selection = req.selection;
+  reply.xselection.target = req.target;
+  reply.xselection.time = req.time;
+  reply.xselection.property = None;
+  XSendEvent(dpy, req.requestor, 0 /* propagate */, 0 /* event mask */, &reply);
+}
+
+void XClipboard::PumpReorderBuffer(std::deque<uint64_t> *reply_order) {
+  for (;;) {
+    reply_order->pop_front();
+    if (reply_order->empty()) {
+      pimpl_->reply_order_map_.erase(j);
+      break;
+    } else {
+      // A pending reply in the reorder buffer might have been blocked on
+      // sending this reply.
+      const std::map<uint64_t, PendingReply>::iterator k =
+        pimpl_->pending_replies_.find(reply_order->front());
+      if (k == pimpl_->pending_replies_.end())
+        break;
+
+      if (k->second.data == NULL) {
+        SendReplyWithFailure(pimpl_->display, k->second.downreq);
+      } else {
+        SendReplyWithContents(pimpl_->display, k->second.downreq,
+                              k->second.data, k->second.length);
+      }
+
+      pimpl_->pending_replies_.erase(k);
+    }
+  }
+}
+
+void XClipboard::ReplyWithFailure(uint64_t tag) {
+  const std::map<uint64_t, InflightDownRequest>::const_iterator i =
+    pimpl_->down_requests.find(tag);
+
+  if (i == pimpl_->down_requests.end())
+    return;
+
+  const ReplyReorderBufferKey reorder_key(i->second);
+  const std::map<ReplyReorderBufferKey, std::deque<uint64_t> >::iterator j =
+    pimpl_->reply_order_map_.find(reorder_key);
+  DCHECK(j != reply_order_map_.end());
+  DCHECK_GT(j->second.size(), 0u);
+
+  if (j->second.front() != tag) {
+    // This reply is out of order. Enqueue it.
+    PendingReply pending(i->second);
+    pimpl_->pending_replies_[tag] = pending;
+    pimpl_->down_requests.erase(i);
+    return;
+  }
+
+  SendReplyWithFailure(pimpl_->display, i->second);
+  pimpl_->down_requests.erase(i);
+  PumpReorderBuffer();
+}
+
+void XClipboard::ReplyWithContents(uint64_t tag, const uint8_t* data,
+                                   size_t length) {
+}