Implemented smooth scrolling using xinput2 in X11.

ui/events/x/device_data_manager_x11.h

Index: ui/events/x/device_data_manager_x11.h
diff --git a/ui/events/x/device_data_manager_x11.h b/ui/events/x/device_data_manager_x11.h
index 02da999a1cdffcc3e89bf43bade9d82183e6ca3c..45549fb01c57c522144026acb5dd317fbadb3bbb 100644
--- a/ui/events/x/device_data_manager_x11.h
+++ b/ui/events/x/device_data_manager_x11.h
@@ -149,6 +149,17 @@ class EVENTS_BASE_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 comes from devices that have a ScrollClass (ie. support
+  // smooth scrolling).
+  bool IsScrollClassEvent(const base::NativeEvent& native_event) const;
+
+  // Check if the device has a vertical ScrollClass
+  bool IsScrollClassVerticalDevice(const base::NativeEvent& native_event) const;
+
+  // Check if the device has a horizontal ScrollClass
+  bool IsScrollClassHorizontalDevice(
+      const base::NativeEvent& native_event) const;
+

[sadrul, 2014/12/22 17:11:12]

Instead of these three, let's have a single

  ScrollType GetScrollClassDetail(event);

where

  enum ScrollType {
    SCROLL_TYPE_NO_SCROLL = 0,
    SCROLL_TYPE_HORIZONTAL = 1 << 0,
    SCROLL_TYPE_VERTICAL = 1 << 1,
  };

   // 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 +182,17 @@ class EVENTS_BASE_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 IsScrollClassEvent.
+  // Pointers shouldn't be NULL.
+  void GetScrollClassOffsets(const base::NativeEvent& native_event,
+                        double* x_offset,
+                        double* y_offset);

[sadrul, 2014/12/22 17:11:12]

indenting is off

+
+  // 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 +230,15 @@ class EVENTS_BASE_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);

[sadrul, 2014/12/22 17:11:12]

indent

+
   // 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(unsigned int deviceid,
@@ -273,6 +304,7 @@ class EVENTS_BASE_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
   // should be processed.
   std::bitset<kMaxDeviceNum> cmt_devices_;
   std::bitset<kMaxDeviceNum> touchpads_;
+  std::bitset<kMaxDeviceNum> scrollclass_devices_;
 
   // A quick lookup table for determining if events from the XI device
   // should be blocked.
@@ -288,6 +320,34 @@ class EVENTS_BASE_EXPORT DeviceDataManagerX11 : public DeviceDataManager {
   // by valuator_lookup_[device_id][data_type].
   std::vector<int> valuator_lookup_[kMaxDeviceNum];
 
+  // Index table to find the horizontal scroll valuator number from the device
+  // ID.
+  int scroll_horizontal_number_[kMaxDeviceNum];
+
+  // Index table to find the vertical scroll valuator number from the device
+  // ID.
+  int scroll_vertical_number_[kMaxDeviceNum];
+
+  // Index table to find the horizontal scroll increment from the device ID.
+  double scroll_horizontal_increment_[kMaxDeviceNum];
+
+  // Index table to find the vertical scroll increment from the device ID.
+  double scroll_vertical_increment_[kMaxDeviceNum];
+
+  // Current horizontal scroll position; used to find the difference between
+  // events.
+  double scroll_horizontal_position_[kMaxDeviceNum];
+
+  // Current vertical scroll position; used to find the difference between
+  // events.
+  double scroll_vertical_position_[kMaxDeviceNum];
+
+  // If true, then a horizontal scroll has been seen on this device.
+  bool scroll_horizontal_seen_[kMaxDeviceNum];
+
+  // If true, then a vertical scroll has been seen on this device.
+  bool scroll_vertical_seen_[kMaxDeviceNum];
+

[sadrul, 2014/12/22 17:11:12]

Having to maintain all these scroll specific info in separate arrays here feels
awkward. How about:

  struct ScrollInfo {
    struct AxisInfo {
      int valuator_id;
      double increment_;
      ...
    };
    AxisInfo vertical, horizontal;
  } scroll_info[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];