X11: Avoid round-tripping to get the cursor position

ui/events/platform/x11/x11_event_source.cc

 // Copyright 2014 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 "ui/events/platform/x11/x11_event_source.h"
 
 #include <X11/Xatom.h>
 #include <X11/XKBlib.h>
 #include <X11/Xlib.h>
 
@@ skipping 78 matching lines @@
 }
 
 }  // namespace
 
 X11EventSource* X11EventSource::instance_ = nullptr;
 
 X11EventSource::X11EventSource(X11EventSourceDelegate* delegate,
                                XDisplay* display)
     : delegate_(delegate),
       display_(display),
-      event_timestamp_(CurrentTime),
       dummy_initialized_(false),
       continue_stream_(true) {
   DCHECK(!instance_);
   instance_ = this;
 
   DCHECK(delegate_);
   DCHECK(display_);
   DeviceDataManagerX11::CreateInstance();
   InitializeXkb(display_);
 }
@@ skipping 67 matching lines @@
   XIfEvent(display_, &event, IsPropertyNotifyForTimestamp,
            reinterpret_cast<XPointer>(&dummy_window_));
 
   UMA_HISTOGRAM_CUSTOM_COUNTS(
       "Linux.X11.ServerRTT", (base::TimeTicks::Now() - start).InMicroseconds(),
       1, base::TimeDelta::FromMilliseconds(50).InMicroseconds(), 50);
   return event.xproperty.time;
 }
 
 Time X11EventSource::GetTimestamp() {
-  if (event_timestamp_ != CurrentTime) {
-    return event_timestamp_;
+  if (!dispatching_events_.empty()) {
+    Time timestamp = ExtractTimeFromXEvent(*dispatching_events_.top());
+    if (timestamp != CurrentTime)
+      return timestamp;
   }
   DVLOG(1) << "Making a round trip to get a recent server timestamp.";
   return GetCurrentServerTime();
 }
 
+base::Optional<gfx::Point>
+X11EventSource::GetRootCursorLocationFromCurrentEvent() const {
+  if (dispatching_events_.empty())
+    return base::nullopt;
+
+  XEvent* event = dispatching_events_.top();
+  bool is_valid_event = false;
+  if (event) {

[sadrul, 2016/10/12 00:17:17]

Should this be a DCHECK()? This should never be null, right?

[Tom (Use chromium acct), 2016/10/12 01:03:27]

Done.

+    switch (event->type) {
+      case ButtonPress:
+      case ButtonRelease:
+      case MotionNotify:
+      case EnterNotify:
+      case LeaveNotify:
+        is_valid_event = true;
+        break;
+      case GenericEvent:
+        if (!ui::TouchFactory::GetInstance()->ShouldProcessXI2Event(event))
+          break;
+        is_valid_event = true;
+    }
+  }
+
+  if (is_valid_event)
+    return ui::EventSystemLocationFromNative(event);
+  return base::nullopt;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // X11EventSource, protected
 
 void X11EventSource::ExtractCookieDataDispatchEvent(XEvent* xevent) {
   bool have_cookie = false;
   if (xevent->type == GenericEvent &&
       XGetEventData(xevent->xgeneric.display, &xevent->xcookie)) {
     have_cookie = true;
   }
 
-  event_timestamp_ = ExtractTimeFromXEvent(*xevent);
+  dispatching_events_.push(xevent);
 
   delegate_->ProcessXEvent(xevent);
   PostDispatchEvent(xevent);
 
-  event_timestamp_ = CurrentTime;
+  dispatching_events_.pop();
 
   if (have_cookie)
     XFreeEventData(xevent->xgeneric.display, &xevent->xcookie);
 }
 
 void X11EventSource::PostDispatchEvent(XEvent* xevent) {
   bool should_update_device_list = false;
 
   if (xevent->type == GenericEvent) {
     if (xevent->xgeneric.evtype == XI_HierarchyChanged) {
@@ skipping 40 matching lines @@
 
 void X11EventSource::OnDispatcherListChanged() {
   if (!hotplug_event_handler_) {
     hotplug_event_handler_.reset(new X11HotplugEventHandler());
     // Force the initial device query to have an update list of active devices.
     hotplug_event_handler_->OnHotplugEvent();
   }
 }
 
 }  // namespace ui