Implemented smooth scrolling using xinput2 in X11.

ui/events/devices/x11/device_data_manager_x11.h

Index: ui/events/devices/x11/device_data_manager_x11.h
diff --git a/ui/events/devices/x11/device_data_manager_x11.h b/ui/events/devices/x11/device_data_manager_x11.h
index 38cb7810517a3bfa137b7832aba39f38ea11698a..01a9f5ff25775f872fb387973820b8f7eddb5c2a 100644
--- a/ui/events/devices/x11/device_data_manager_x11.h
+++ b/ui/events/devices/x11/device_data_manager_x11.h
@@ -40,6 +40,30 @@ enum GestureMetricsType {
   kGestureMetricsTypeUnknown,
 };
 
+// Information about scroll valuators
+struct ScrollInfo {
+  struct AxisInfo {
+    // The scroll valuator number of this scroll axis.
+    int number;
+    // The scroll increment; a value of n indicates n movement equals one
+    // traditional scroll unit.
+    double increment;
+    // Current scroll position; used to find the difference between events.
+    double position;
+    // If true then scroll has been seen in this direction.
+    bool seen;
+  };
+
+  AxisInfo vertical, horizontal;
+};
+
+// A bitfield describing which scroll axes are enabled for a device.
+enum ScrollType {
+  SCROLL_TYPE_NO_SCROLL = 0,
+  SCROLL_TYPE_HORIZONTAL = 1 << 0,
+  SCROLL_TYPE_VERTICAL = 1 << 1,
+};
+
 // A class that extracts and tracks the input events data. It currently handles
 // mouse, touchpad and touchscreen devices.
 class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
@@ -119,6 +143,16 @@ class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
   // Updates the list of devices.
   void UpdateDeviceList(Display* display);
 
+  // Updates a device based on a Valuator class info. Returns true if the
+  // device is a possible CMT device.
+  bool UpdateValuatorClassDevice(XIValuatorClassInfo* valuator_class_info,
+                                 Atom *atoms,
+                                 int deviceid);

[sadrul, 2015/08/18 16:57:46]

This doesn't need to be public, does it?

[Will Shackleton, 2015/08/26 19:52:48]

Acknowledged.

+
+  // Updates a device based on a Scroll class info.
+  void UpdateScrollClassDevice(XIScrollClassInfo* scroll_class_info,
+                               int deviceid);

[sadrul, 2015/08/18 16:57:46]

ditto

[Will Shackleton, 2015/08/26 19:52:48]

Acknowledged.

+
   // For multitouch events we use slot number to distinguish touches from
   // different fingers. This function returns true if the associated slot
   // for |xiev| can be found and it is saved in |slot|, returns false if
@@ -149,6 +183,16 @@ class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
   // is a CMT event (e.g. it could be a mouse pointer move).
   bool IsCMTDeviceEvent(const base::NativeEvent& native_event) const;
 
+  // Check if the event contains information about a ScrollClass, and
+  // report which scroll axes are contained in this event, defined by
+  // ScrollInfo.
+  int GetScrollClassEventDetail(const base::NativeEvent& native_event) const;
+
+  // Check if the event comes from a device that has a ScrollClass, and
+  // report which scroll axes it supports as a bit field, defined by
+  // ScrollInfo.
+  int GetScrollClassDeviceDetail(const base::NativeEvent& native_event) const;
+
   // Check if the event is one of the CMT gesture events (scroll, fling,
   // metrics etc.).
   bool IsCMTGestureEvent(const base::NativeEvent& native_event) const;
@@ -171,6 +215,17 @@ class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
                         float* y_offset_ordinal,
                         int* finger_count);
 
+  // Extract data from a scroll class event (smooth scrolling). User must
+  // first verify the event type with GetScrollClassEventDetail.
+  // Pointers shouldn't be NULL.
+  void GetScrollClassOffsets(const base::NativeEvent& native_event,
+                             double* x_offset,
+                             double* y_offset);
+
+  // Invalidate stored scroll class counters, since they can change when
+  // pointing at other windows.
+  void InvalidateScrollClasses();
+
   // Extract data from a fling event. User must first verify the event type
   // with IsFlingEvent. Pointers shouldn't be NULL.
   void GetFlingData(const base::NativeEvent& native_event,
@@ -208,6 +263,15 @@ class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
                      const DataType type,
                      double* value);
 
+  // Normalize the scroll amount according to the increment size.
+  // *value /= increment
+  // *value is expected to be 1 or -1.
+  // Returns true and sets the normalized value in |value| if normalization is
+  // successful. Returns false and |value| is unchanged otherwise.
+  bool NormalizeScrollData(unsigned int deviceid,
+                           bool horizontal,
+                           double* value);
+
   // Extract the range of the data type. Return true if the range is available
   // and written into min & max, false if the range is not available.
   bool GetDataRange(int deviceid,
@@ -277,6 +341,7 @@ class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
   // should be processed.
   std::bitset<kMaxDeviceNum> cmt_devices_;
   std::bitset<kMaxDeviceNum> touchpads_;
+  std::bitset<kMaxDeviceNum> scrollclass_devices_;
 
   // List of the master pointer devices.
   std::vector<int> master_pointers_;
@@ -295,6 +360,10 @@ class EVENTS_DEVICES_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
   // by valuator_lookup_[device_id][data_type].
   std::vector<int> valuator_lookup_[kMaxDeviceNum];
 
+  // Index table to find the horizontal and vertical scroll valuator
+  // numbers, scroll increments and scroll position.
+  ScrollInfo scroll_data_[kMaxDeviceNum];
+
   // Index table to find the DataType for valuator on the specific device
   // by data_type_lookup_[device_id][valuator].
   std::vector<int> data_type_lookup_[kMaxDeviceNum];