Added a command line switch to disable xinput2, enabled xinput2 by default

ui/events/devices/x11/device_data_manager_x11.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/devices/x11/device_data_manager_x11.h"
 
 #include <stddef.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/Xlib.h>
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/command_line.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/singleton.h"
 #include "base/sys_info.h"
 #include "build/build_config.h"
 #include "ui/display/display.h"
 #include "ui/events/devices/x11/device_list_cache_x11.h"
 #include "ui/events/devices/x11/touch_factory_x11.h"
+#include "ui/events/devices/x11/ui_events_devices_x11_switches.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_switches.h"
 #include "ui/events/keycodes/keyboard_code_conversion_x.h"
 #include "ui/gfx/geometry/point3_f.h"
 #include "ui/gfx/x/x11_types.h"
 
 // XIScrollClass was introduced in XI 2.1 so we need to define it here
 // for backward-compatibility with older versions of XInput.
 #if !defined(XIScrollClass)
 #define XIScrollClass 3
@@ skipping 83 matching lines @@
 
 template <typename Iterator>
 Iterator FindDeviceWithId(Iterator begin, Iterator end, int id) {
   for (auto it = begin; it != end; ++it) {
     if (it->id == id)
       return it;
   }
   return end;
 }
 
+bool IsHighPrecisionScrollingDisabled() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kDisableHighPrecisionScrolling);
+}
+
 }  // namespace
 
 bool DeviceDataManagerX11::IsCMTDataType(const int type) {
   return (type >= kCMTDataTypeStart) && (type <= kCMTDataTypeEnd);
 }
 
 bool DeviceDataManagerX11::IsTouchDataType(const int type) {
   return (type >= kTouchDataTypeStart) && (type <= kTouchDataTypeEnd);
 }
 
@@ skipping 11 matching lines @@
   set_instance(device_data_manager);
 }
 
 // static
 DeviceDataManagerX11* DeviceDataManagerX11::GetInstance() {
   return static_cast<DeviceDataManagerX11*>(DeviceDataManager::GetInstance());
 }
 
 DeviceDataManagerX11::DeviceDataManagerX11()
     : xi_opcode_(-1),
+      high_precision_scrolling_disabled_(IsHighPrecisionScrollingDisabled()),
       atom_cache_(gfx::GetXDisplay(), kCachedAtoms),
       button_map_count_(0) {
   CHECK(gfx::GetXDisplay());
   InitializeXInputInternal();
 
   // Make sure the sizes of enum and kCachedAtoms are aligned.
   CHECK(arraysize(kCachedAtoms) == static_cast<size_t>(DT_LAST_ENTRY) + 1);
   UpdateDeviceList(gfx::GetXDisplay());
   UpdateButtonMap();
 }
@@ skipping 596 matching lines @@
   valuator_max_[deviceid][data_type] = valuator_class_info->max;
   return IsCMTDataType(data_type);
 }
 
 void DeviceDataManagerX11::UpdateScrollClassDevice(
     XIScrollClassInfo* scroll_class_info,
     int deviceid) {
   DCHECK(deviceid >= 0 && deviceid < kMaxDeviceNum);
   ScrollInfo& info = scroll_data_[deviceid];
 
-  // TODO: xinput2 is disabled until edge cases are fixed.
-  // http://crbug.com/616308
-  return;
+  if (high_precision_scrolling_disabled_) {
+    return;
+  }

[sadrul, 2016/07/20 17:02:26]

no {}

Move after the DCHECK() above

[Will Shackleton, 2016/07/25 20:53:38]

Done.

 
   bool legacy_scroll_available =
       (scroll_class_info->flags & XIScrollFlagNoEmulation) == 0;
   // If the device's highest resolution is lower than the resolution of xinput1
   // then use xinput1's events instead (ie. don't configure smooth scrolling).
   if (legacy_scroll_available &&
       std::abs(scroll_class_info->increment) <= 1.0) {
     return;
   }
 
@@ skipping 97 matching lines @@
     } else {
       keyboards.erase(it);
       ++blocked_iter;
     }
   }
   // Notify base class of updated list.
   DeviceDataManager::OnKeyboardDevicesUpdated(keyboards);
 }
 
 }  // namespace ui