Add generic mapping for gamepad

ui/events/ozone/gamepad/generic_gamepad_mapping.cc

+// Copyright 2017 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 <linux/input.h>
+#include <cstdint>
+#include <list>
+#include <set>
+#include <vector>
+
+#include "base/macros.h"
+#include "ui/events/ozone/evdev/event_device_info.h"
+#include "ui/events/ozone/gamepad/generic_gamepad_mapping.h"
+#include "ui/events/ozone/gamepad/webgamepad_constants.h"
+
+namespace ui {
+// This helper class is used to generate generic mapping.
+class GenericMappingHelper {
+ public:
+  GenericMappingHelper(const EventDeviceInfo& devinfo,

[spang, 2017/06/01 05:08:12]

This organization is surprising. Everything happens in the ctor, but once it
finishes, the constructed object is not needed.

Can you organize this a different way. Something like

class GamepadMapperBuilder {
 public:
  void MapButton(uint16_t from_button, WebGamepadButtonType to_button) {
    DCHECK(HasMappingFromButton(from_button));
    DCHECK(HasMappingToButton(to_button));
    ...
  }

  void MapAbsoluteAxis(uint16_t from_absolute_axis, WebGamepadAbsType to_axis) {
    DCHECK(HasMappingFromAbsoluteAxis(from_absolute_axis));
    DCHECK(HasMappingToAxis(to_axis));
    ...
  }

  // etc

  std::unique_ptr<GamepadMapping> ToGamepadMapping() {
    // build final mapper from button_mapping_ & absolute_axis_mapping_
  }
  

 private:
  std::bitset<something> mapped_buttons_;
  std::bitset<something> mapped_absolute_axes_;
  std::vector<KeyMapEntry> button_mapping_;
  std::vector<AbsMapEntry> absolute_axis_mapping_;
};

std::unique_ptr<GamepadMapping> BuildGamepadMapper(const EventDeviceInfo& info)
{
  GamepadMapperBuilder builder;

  // Run logic from previous ctor using |info| and |builder|

  return builder.ToGamepadMapping();
}

[jkwang, 2017/06/02 22:03:52]

Done.

+                       std::vector<AbsMapEntry>* abs_map,
+                       std::vector<KeyMapEntry>* key_map)
+      : devinfo_(devinfo), abs_map_(abs_map), key_map_(key_map) {
+    for (uint16_t i = 0; i < WG_BUTTON_COUNT; i++) {
+      unmapped_wg_btn_.push_back(i);

[spang, 2017/06/01 05:08:13]

bitset

with a vector this should call reserve() if you know the final size.

[jkwang, 2017/06/02 22:03:51]

Done.

+    }
+
+    for (uint16_t i = 0; i < WG_ABS_COUNT; i++) {
+      unmapped_wg_abs_.push_back(i);
+    }
+    MapAbs();
+    MapBtns();
+  }
+
+ private:
+  // MapAbs will map all the abs events.
+  void MapAbs() {

[spang, 2017/06/01 05:08:13]

Although linux uses btn and abs Google style is to avoid abbreviations. Possibly
"WG" in the constant names should be fixed too.

MapAbsoluteAxes ?

[jkwang, 2017/06/02 22:03:51]

Done.

+    TryMapHat();
+    TryMapTrigger();
+    MapOtherAbs();
+  }
+
+  // MapBtns will map all the btn events.
+  void MapBtns() {

[spang, 2017/06/01 05:08:12]

MapButtons()

[jkwang, 2017/06/02 22:03:51]

Done.

+    // Map Mode.
+    StaticMapBtnTo(BTN_MODE, WG_BUTTON_MODE);
+    // Special care for adt style select/start.
+    StaticMapBtnTo(KEY_BACK, WG_BUTTON_SELECT);
+    StaticMapBtnTo(KEY_HOMEPAGE, WG_BUTTON_START);
+
+    // In linux kernel, joydev.c map evdev events in the same way.
+    for (int i = BTN_JOYSTICK - BTN_MISC; i < KEY_MAX - BTN_MISC + 1; i++) {
+      int code = i + BTN_MISC;

[spang, 2017/06/01 05:08:12]

Confused by this - what's "i" for here (Why not iterate over code) and why does
this test all the keyboard keys? Are there actually gamepads with keyboard keys
on them that should get mapped to gamepad buttons?

[jkwang, 2017/06/02 22:03:51]

As the comments, it's
https://github.com/spotify/linux/blob/master/drivers/input/joydev.c starting
from line 816.

+      if (unmapped_wg_btn_.empty()) {
+        return;
+      }
+
+      if (devinfo_.HasKeyEvent(code) && !mapped_ev_btn_.count(code)) {

[spang, 2017/06/01 05:08:13]

This would read a lot more clearly if you make a function called

bool IsButtonMapped(uint16_t code)

and use that (and below)

[jkwang, 2017/06/02 22:03:52]

Done.

+        key_map_->push_back({code, unmapped_wg_btn_.front()});
+        unmapped_wg_btn_.pop_front();
+      }
+    }
+
+    for (int i = 0; i < BTN_JOYSTICK - BTN_MISC; i++) {
+      int code = i + BTN_MISC;
+      if (unmapped_wg_btn_.empty()) {
+        return;
+      }
+
+      if (devinfo_.HasKeyEvent(code) && !mapped_ev_btn_.count(code)) {
+        key_map_->push_back({code, unmapped_wg_btn_.front()});
+        unmapped_wg_btn_.pop_front();
+      }
+    }
+  }
+
+  void StaticMapBtnTo(uint16_t ev_code, uint16_t wg_code) {
+    if (devinfo_.HasKeyEvent(ev_code)) {
+      key_map_->push_back({ev_code, wg_code});
+      unmapped_wg_btn_.remove(wg_code);
+      mapped_ev_btn_.insert(ev_code);
+    }
+  }
+
+  // We always want to map HAT0X and HAT0Y to DPAD.
+  void TryMapHat() {
+    if (!devinfo_.HasAbsEvent(ABS_HAT0X) || !devinfo_.HasAbsEvent(ABS_HAT0Y)) {
+      return;
+    }
+
+    unmapped_wg_btn_.remove(WG_BUTTON_DPAD_UP);
+    unmapped_wg_btn_.remove(WG_BUTTON_DPAD_DOWN);
+    unmapped_wg_btn_.remove(WG_BUTTON_DPAD_LEFT);
+    unmapped_wg_btn_.remove(WG_BUTTON_DPAD_RIGHT);
+
+    mapped_ev_abs_.insert(ABS_HAT0X);
+    mapped_ev_abs_.insert(ABS_HAT0Y);
+
+    abs_map_->push_back(TO_BTN(ABS_HAT0X, kHAT_X));
+    abs_map_->push_back(TO_BTN(ABS_HAT0Y, kHAT_Y));
+  }
+
+  void TryMapTrigger() {
+    // ABS_BRAKE, ABS_GAS style.
+    if (devinfo_.HasAbsEvent(ABS_BRAKE) && devinfo_.HasAbsEvent(ABS_GAS)) {
+      abs_map_->push_back(TO_BTN(ABS_BRAKE, WG_BUTTON_LT));
+      abs_map_->push_back(TO_BTN(ABS_GAS, WG_BUTTON_RT));
+
+      mapped_ev_abs_.insert(ABS_BRAKE);
+      mapped_ev_abs_.insert(ABS_GAS);
+      unmapped_wg_btn_.remove(WG_BUTTON_LT);
+      unmapped_wg_btn_.remove(WG_BUTTON_RT);
+
+      return;
+    }
+
+    // XInput style: If X,Y,Z,RX,RY,RZ are all there, Z and RZ are triggers.
+    if (devinfo_.HasAbsEvent(ABS_X) && devinfo_.HasAbsEvent(ABS_Y) &&
+        devinfo_.HasAbsEvent(ABS_Z) && devinfo_.HasAbsEvent(ABS_RX) &&
+        devinfo_.HasAbsEvent(ABS_RY) && devinfo_.HasAbsEvent(ABS_RZ)) {
+      abs_map_->push_back(TO_BTN(ABS_Z, WG_BUTTON_LT));

[spang, 2017/06/01 05:08:13]

Can you make more functions to make this read well and less error prone.
Something like

AddButtonMapping(ABS_Z, WG_BUTTON_LT);

[jkwang, 2017/06/02 22:03:52]

Done.

+      abs_map_->push_back(TO_BTN(ABS_RZ, WG_BUTTON_RT));
+      mapped_ev_abs_.insert(ABS_Z);
+      mapped_ev_abs_.insert(ABS_RZ);
+      unmapped_wg_btn_.remove(WG_BUTTON_LT);
+      unmapped_wg_btn_.remove(WG_BUTTON_RT);
+    }
+  }
+
+  // Map other Abs in the Joydev style.
+  void MapOtherAbs() {
+    for (int code = 0; code < ABS_CNT; ++code) {
+      if (unmapped_wg_abs_.empty()) {
+        return;
+      }
+
+      if (devinfo_.HasAbsEvent(code) && !mapped_ev_abs_.count(code)) {
+        abs_map_->push_back(TO_ABS(code, unmapped_wg_abs_.front()));
+        unmapped_wg_abs_.pop_front();
+      }
+    }
+  }
+
+  const EventDeviceInfo& devinfo_;
+  // Webgamepad button and abs remain unmapped.
+  std::list<uint16_t> unmapped_wg_btn_;

[spang, 2017/06/01 05:08:13]

You can use a std::bitset here. Or std::vector. std::list is very inefficient
for this task.

[jkwang, 2017/06/02 22:03:51]

Done.

+  std::list<uint16_t> unmapped_wg_abs_;
+  // Evdev btn and abs that are already mapped.
+  std::set<uint16_t> mapped_ev_btn_;

[spang, 2017/06/01 05:08:13]

Also bitset

[jkwang, 2017/06/02 22:03:51]

Done.

+  std::set<uint16_t> mapped_ev_abs_;
+
+  std::vector<AbsMapEntry>* abs_map_;
+  std::vector<KeyMapEntry>* key_map_;
+};
+
+GenericGamepadMapping::GenericGamepadMapping(
+    const EventDeviceInfo& device_info) {
+  GenericMappingHelper(device_info, &abs_map_, &key_map_);
+}
+
+GenericGamepadMapping::~GenericGamepadMapping() {}
+
+bool GenericGamepadMapping::operator()(uint16_t type,
+                                       uint16_t code,
+                                       GamepadEventType* mapped_type,
+                                       uint16_t* mapped_code) {
+  if (type == EV_KEY) {
+    for (auto entry : key_map_) {
+      if (entry.evdev_code == code) {
+        *mapped_type = GamepadEventType::BUTTON;
+        *mapped_code = entry.mapped_code;
+        return true;
+      }
+    }
+    return false;
+  }
+
+  if (type == EV_ABS) {
+    for (auto entry : abs_map_) {
+      if (entry.evdev_code == code) {
+        *mapped_type = entry.mapped_type;
+        *mapped_code = entry.mapped_code;
+        return true;
+      }
+    }
+    return false;
+  }
+  return false;
+};
+
+}  // namespace ui