ozone: evdev: Add gamepad support

ui/events/ozone/evdev/gamepad_event_converter_evdev.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/ozone/evdev/gamepad_event_converter_evdev.h"
+
+#include <errno.h>
+#include <linux/input.h>
+#include <stddef.h>
+
+#include "base/trace_event/trace_event.h"
+#include "ui/events/devices/stylus_state.h"
+#include "ui/events/event.h"
+#include "ui/events/event_utils.h"
+#include "ui/events/keycodes/dom/keycode_converter.h"
+#include "ui/events/ozone/evdev/device_event_dispatcher_evdev.h"
+#include "ui/events/ozone/evdev/scoped_input_device.h"
+#include "ui/events/webgamepad_constants.h"
+
+namespace ui {
+
+GamepadEventConverterEvdev::GamepadEventConverterEvdev(
+    ScopedInputDevice fd,
+    base::FilePath path,
+    int id,
+    const EventDeviceInfo& devinfo,
+    DeviceEventDispatcherEvdev* dispatcher)
+    : EventConverterEvdev(fd.get(),
+                          path,
+                          id,
+                          devinfo.device_type(),
+                          devinfo.name(),
+                          devinfo.vendor_id(),
+                          devinfo.product_id()),
+      will_send_frame_(false),
+      input_device_fd_(std::move(fd)),
+      dispatcher_(dispatcher) {
+  // In order to map gamepad, we have to save the abs_info from device_info
+  // and get the gamepad_mapping.
+  for (int code = 0; code < ABS_CNT; ++code) {
+    abs_info_[code] = devinfo.GetAbsInfoByCode(code);
+    if (devinfo.HasAbsEvent(code)) {
+      // Set the minimum fuzz. For example, if min is 0 and max is 255, we can't
+      // determine if 127 is 0.0 or 128 is 0.0. We will just fuzz by one percent
+      // to make them both zero. If (max - min) is less than zero, we won't do
+      // this override because we don't want to cause too much error.
+      if (abs_info_[code].fuzz == 0) {
+        abs_info_[code].fuzz =
+            (abs_info_[code].maximum - abs_info_[code].minimum) / 100;
+      }
+
+      // Some gamepad report garbage flat value. To map approprate value to
+      // exactly 0.0, we need the flat value to be fixed.  We assume the flat is
+      // in the middle of minimum and maximum if it's not min.
+      if (abs_info_[code].flat != abs_info_[code].minimum) {
+        abs_info_[code].flat =
+            (abs_info_[code].maximum + abs_info_[code].minimum) / 2;
+      }
+    }
+  }
+  gamepad_mapping_ =
+      GetGamepadMapping(devinfo.vendor_id(), devinfo.product_id());
+}
+
+GamepadEventConverterEvdev::~GamepadEventConverterEvdev() {
+  DCHECK(!enabled_);
+}
+
+bool GamepadEventConverterEvdev::HasGamepad() const {
+  return true;
+}
+
+void GamepadEventConverterEvdev::OnFileCanReadWithoutBlocking(int fd) {
+  TRACE_EVENT1("evdev",
+               "GamepadEventConverterEvdev::OnFileCanReadWithoutBlocking", "fd",
+               fd);
+  while (true) {
+    input_event input;
+    ssize_t read_size = read(fd, &input, sizeof(input));
+    if (read_size != sizeof(input)) {
+      if (errno == EINTR || errno == EAGAIN)
+        return;
+      if (errno != ENODEV)
+        PLOG(ERROR) << "error reading device " << path_.value();
+      Stop();
+      return;
+    }
+
+    if (!enabled_)
+      return;
+
+    ProcessEvent(input);
+  }
+}
+void GamepadEventConverterEvdev::OnDisabled() {
+  ResetGamepad();
+}
+
+void GamepadEventConverterEvdev::ProcessEvent(const input_event& evdev_ev) {
+  // We may have missed Gamepad releases. Reset everything.
+  // If the event is sync, we send a frame.
+  if (evdev_ev.type == EV_SYN) {
+    if (evdev_ev.code == SYN_DROPPED) {
+      LOG(WARNING) << "kernel dropped input events";
+      ResetGamepad();

[spang, 2017/04/13 00:52:19]

Should sync using EVIOCGABS and EVIOCGKEY here.

[jkwang, 2017/04/19 19:42:23]

Sounds reasonable. But this will be a rare corner case, I am trying to just
pretend everything is released and prevent something annoying (character keep
moving in one direction). I think it will be good enough for gaming.

[spang, 2017/04/21 05:38:46]

I still think we should do this right for absolute inputs at least; it's not too
hard. Otherwise we're stuck returning wrong data sometimes.

Suppose one of the axes is a throttle with no spring in it and it's set to
"max". Then not syncing the initial state means you'll return 0.0, instead of
1.0, until the user goes and wiggles the control so that it changes value. Some
absoute inputs are not spring loaded to return to center.

It's the same code on startup as on SYN_DROPPED. Look at the MT code for an
example for how to do it (TouchEventConverterEvdev::Initialize).

I don't care as much about syncing keys since it'd only matter if you're holding
them down.

[jkwang, 2017/04/25 21:16:41]

Done.

+    } else if (evdev_ev.code == SYN_REPORT) {
+      OnSync(TimeTicksFromInputEvent(evdev_ev));
+    }
+    return;
+  }
+
+  GamepadEventType mapped_type;
+  uint16_t mapped_code;
+
+  // We are going to search the event in the mapping.
+  bool found_map = false;
+  for (size_t i = 0; i < gamepad_mapping_->size(); ++i) {

[spang, 2017/04/13 00:52:19]

Can you do do the mapping once at startup so that we don't need to iterate the
entire map for every event?

[jkwang, 2017/04/19 19:42:23]

Done.

+    const GamepadMappingEntry& map_entry_ = (*gamepad_mapping_)[i];
+    if (evdev_ev.type == map_entry_.evdev_type &&
+        evdev_ev.code == map_entry_.evdev_code) {
+      found_map = true;
+      mapped_type = map_entry_.mapped_type;
+      mapped_code = map_entry_.mapped_code;
+    }
+  }
+
+  // If we cannot find a map for this event, it will be discarded.
+  if (!found_map) {
+    return;
+  }
+
+  // If it's btn -> btn mapping, we can send the event and return now.
+  if (mapped_type == GamepadEventType::BUTTON && evdev_ev.type == EV_KEY) {
+    OnButtonChange(mapped_code, evdev_ev.value,
+                   TimeTicksFromInputEvent(evdev_ev));
+    return;
+  }
+
+  double mapped_abs_value;
+  double mapped_abs_min = kWebGamepadJoystickMin;
+  double mapped_abs_max = kWebGamepadJoystickMax;
+  // If the mapped event is a trigger, we set the min and max to trigger
+  // min/max.
+  if (mapped_code == WG_BUTTON_L2 || mapped_code == WG_BUTTON_R2) {

[spang, 2017/04/21 05:38:46]

Shouldn't this kind of stuff go in the mapping?

[jkwang, 2017/04/25 21:16:41]

This is fixed, when the mapped axis is L2 or R2 the range will be 0.0 to 1.0.
Other axis range is -1.0 to 1.0.

+    mapped_abs_min = kWebGamepadTriggerMin;
+    mapped_abs_max = kWebGamepadTriggerMax;
+  }
+
+  // Code is out of ABS_MAX. This should not happen, but we don't want a gamepad
+  // reporting wrong values break the code.
+  if (evdev_ev.code < 0 || evdev_ev.code > ABS_MAX) {
+    return;
+  }
+
+  struct input_absinfo& abs_info = abs_info_[evdev_ev.code];
+  // To remove noise, the value must change at least by fuzz.

[spang, 2017/04/13 00:52:19]

This is kinda odd, why do we get values within |fuzz| if we're just going to
drop them? What does Android do with |fuzz| ?

[jkwang, 2017/04/19 19:42:23]

We have to read in the values and decide whether we drop it. Android is not
doing this. And some game will thus behave weird when a gamepad with wrong fuzz
is connected. For example, a gamepad report hat0x with abs_min = 0, abs_max =
255, flat = 0, fuzz = 0. The actual flat value is 128. This axis will always be
a small double value in android. It will be hard to sanitize data after mapping,
so we would better do it here.

+  if (evdev_ev.value > abs_info.value - abs_info.fuzz &&
+      evdev_ev.value < abs_info.value + abs_info.fuzz) {
+    return;
+  }
+
+  // Save the old value for later use.
+  int old_value = abs_info.value;
+  // If the value of input is within the range of [flat - fuzz, flat + fuzz],
+  // the value is discarded and we are going to use 0.
+  if (evdev_ev.value >= abs_info.flat - abs_info.fuzz &&
+      evdev_ev.value <= abs_info.flat + abs_info.fuzz) {
+    abs_info.value = abs_info.flat;
+    mapped_abs_value = 0.0;
+  } else if (evdev_ev.value <= abs_info.minimum + abs_info.fuzz) {
+    // We are manually set min and max to ensure double value equals.
+    abs_info.value = abs_info.minimum;
+    mapped_abs_value = mapped_abs_min;
+  } else if (evdev_ev.value >= abs_info.maximum - abs_info.fuzz) {
+    abs_info.value = abs_info.maximum;
+    mapped_abs_value = mapped_abs_max;
+  } else {
+    abs_info.value = evdev_ev.value;
+    // Check if the min == max to avoid divide by zero. If min == max, we are
+    // going to discard this event.
+    if (abs_info.minimum == abs_info.maximum) {
+      return;
+    }
+    mapped_abs_value =
+        mapped_abs_min +
+        (mapped_abs_max - mapped_abs_min) *
+            static_cast<double>(evdev_ev.value - abs_info.minimum) /
+            static_cast<double>(abs_info.maximum - abs_info.minimum);
+  }
+
+  // If the mapped type is abs, we can send it now.
+  if (mapped_type == GamepadEventType::AXIS) {
+    OnAbsChange(mapped_code, mapped_abs_value,
+                TimeTicksFromInputEvent(evdev_ev));
+    return;
+  }
+
+  // We need to map HAT to DPAD depend on the state of the axis.
+  if (mapped_code == kHAT_X) {
+    if (mapped_abs_value < 0.0 ||
+        (mapped_abs_value == 0.0 && old_value < abs_info.flat)) {
+      // If current HAT_X is < 0 or it was <0 before it's dpad left.
+      mapped_code = WG_BUTTON_DPAD_LEFT;
+    } else {
+      mapped_code = WG_BUTTON_DPAD_RIGHT;
+    }
+  } else if (mapped_code == kHAT_Y) {
+    if (mapped_abs_value < 0 ||
+        (mapped_abs_value == 0.0 && old_value < abs_info.flat)) {
+      mapped_code = WG_BUTTON_DPAD_UP;
+    } else {
+      mapped_code = WG_BUTTON_DPAD_DOWN;
+    }
+  }
+  OnButtonChange(mapped_code, mapped_abs_value,
+                 TimeTicksFromInputEvent(evdev_ev));
+}
+
+void GamepadEventConverterEvdev::ResetGamepad() {
+  base::TimeTicks timestamp = ui::EventTimeForNow();
+  for (int btn_code = 0; btn_code < kWebGamepadBtnCnt; ++btn_code) {
+    OnButtonChange(btn_code, 0, timestamp);
+  }
+
+  for (int abs_code = 0; abs_code < kWebGamepadAbsCnt; ++abs_code) {
+    OnAbsChange(abs_code, 0, timestamp);
+  }
+  OnSync(timestamp);
+}
+
+void GamepadEventConverterEvdev::OnButtonChange(
+    unsigned int code,
+    double value,
+    const base::TimeTicks& timestamp) {
+  EventType type;
+  if (value == 0.0) {
+    type = ET_GAMEPAD_BTN_RELEASED;
+  } else {
+    type = ET_GAMEPAD_BTN_PRESSED;
+  }
+
+  dispatcher_->DispatchGamepadEvent(
+      GamepadEventParams(input_device_.id, type, value, code, timestamp));
+  will_send_frame_ = true;
+}
+
+void GamepadEventConverterEvdev::OnAbsChange(unsigned int code,
+                                             double value,
+                                             const base::TimeTicks& timestamp) {
+  dispatcher_->DispatchGamepadEvent(GamepadEventParams(
+      input_device_.id, ET_GAMEPAD_ABS_MOVED, value, code, timestamp));
+  will_send_frame_ = true;
+}
+
+void GamepadEventConverterEvdev::OnSync(const base::TimeTicks& timestamp) {
+  if (will_send_frame_) {
+    // Dispatch gamepad frame.
+    dispatcher_->DispatchGamepadEvent(GamepadEventParams(
+        input_device_.id, ET_GAMEPAD_FRAME, 0.0, 0, timestamp));
+
+    will_send_frame_ = false;
+  }
+}
+
+}  // namespace ui