Support DirectInput gamepads on Windows.

content/browser/gamepad/gamepad_platform_data_fetcher_win.cc

 // Copyright (c) 2012 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 "content/browser/gamepad/gamepad_platform_data_fetcher_win.h"
 
+#include <dinput.h>
+#include <dinputd.h>
+
 #include "base/debug/trace_event.h"
+#include "base/stringprintf.h"
 #include "content/common/gamepad_messages.h"
 #include "content/common/gamepad_hardware_buffer.h"
 
 namespace content {
 
 using namespace WebKit;
 
 namespace {
 
 // See http://goo.gl/5VSJR. These are not available in all versions of the
 // header, but they can be returned from the driver, so we define our own
 // versions here.
 static const BYTE kDeviceSubTypeGamepad = 1;
 static const BYTE kDeviceSubTypeWheel = 2;
 static const BYTE kDeviceSubTypeArcadeStick = 3;
 static const BYTE kDeviceSubTypeFlightStick = 4;
 static const BYTE kDeviceSubTypeDancePad = 5;
 static const BYTE kDeviceSubTypeGuitar = 6;
 static const BYTE kDeviceSubTypeGuitarAlternate = 7;
 static const BYTE kDeviceSubTypeDrumKit = 8;
 static const BYTE kDeviceSubTypeGuitarBass = 11;
 static const BYTE kDeviceSubTypeArcadePad = 19;
 
-float NormalizeAxis(SHORT value) {
+float NormalizeXInputAxis(SHORT value) {
   return ((value + 32768.f) / 32767.5f) - 1.f;
 }
 
 const WebUChar* const GamepadSubTypeName(BYTE sub_type) {
   switch (sub_type) {
     case kDeviceSubTypeGamepad: return L"GAMEPAD";
     case kDeviceSubTypeWheel: return L"WHEEL";
     case kDeviceSubTypeArcadeStick: return L"ARCADE_STICK";
     case kDeviceSubTypeFlightStick: return L"FLIGHT_STICK";
     case kDeviceSubTypeDancePad: return L"DANCE_PAD";
     case kDeviceSubTypeGuitar: return L"GUITAR";
     case kDeviceSubTypeGuitarAlternate: return L"GUITAR_ALTERNATE";
     case kDeviceSubTypeDrumKit: return L"DRUM_KIT";
     case kDeviceSubTypeGuitarBass: return L"GUITAR_BASS";
     case kDeviceSubTypeArcadePad: return L"ARCADE_PAD";
     default: return L"<UNKNOWN>";
   }
 }
 
+bool GetDirectInputVendorProduct(IDirectInputDevice8* gamepad,
+                                 std::string* vendor,
+                                 std::string* product) {
+  DIPROPDWORD prop;
+  prop.diph.dwSize = sizeof(DIPROPDWORD);
+  prop.diph.dwHeaderSize = sizeof(DIPROPHEADER);
+  prop.diph.dwObj = 0;
+  prop.diph.dwHow = DIPH_DEVICE;
+
+  if (FAILED(gamepad->GetProperty(DIPROP_VIDPID, &prop.diph)))
+    return false;
+  *vendor = base::StringPrintf("%04x", LOWORD(prop.dwData));
+  *product = base::StringPrintf("%04x", HIWORD(prop.dwData));
+  return true;
+}
+
+// Sets the deadzone value for all axes of a gamepad.
+// deadzone values range from 0 (no deadzone) to 10,000 (entire range
+// is dead).
+bool SetDirectInputDeadZone(IDirectInputDevice8* gamepad,
+                            int deadzone) {
+  DIPROPDWORD prop;
+  prop.diph.dwSize = sizeof(DIPROPDWORD);
+  prop.diph.dwHeaderSize = sizeof(DIPROPHEADER);
+  prop.diph.dwObj = 0;
+  prop.diph.dwHow = DIPH_DEVICE;
+  prop.dwData = deadzone;
+  return SUCCEEDED(gamepad->SetProperty(DIPROP_DEADZONE, &prop.diph));
+}
+
+struct InternalDirectInputDevice {
+  IDirectInputDevice8* gamepad;
+  GamepadStandardMappingFunction mapper;
+  wchar_t id[WebGamepad::idLengthCap];
+  GUID guid;
+};
+
+struct EnumDevicesContext {
+  IDirectInput8* directinput_interface;
+  std::vector<InternalDirectInputDevice>* directinput_devices;
+};
+
+// We define our own data format structure to attempt to get as many
+// axes as possible.
+struct JoyData {
+  long axes[10];
+  char buttons[24];
+  DWORD pov;  // Often used for D-pads.
+};
+
+BOOL CALLBACK DirectInputEnumDevicesCallback(const DIDEVICEINSTANCE* instance,
+                                             void* context) {
+  EnumDevicesContext* ctxt = (EnumDevicesContext*) context;

[scottmg, 2013/02/19 18:50:52]

reinterpret_cast

[teravest, 2013/02/19 20:53:37]

Done.

+  IDirectInputDevice8* gamepad;
+
+  if (FAILED(ctxt->directinput_interface->CreateDevice(instance->guidInstance,
+                                                       &gamepad,
+                                                       NULL)))
+    return DIENUM_CONTINUE;
+
+  gamepad->Acquire();
+
+#define MAKE_AXIS(i) \
+  {0, FIELD_OFFSET(JoyData, axes) + 4 * i, \
+   DIDFT_AXIS | DIDFT_MAKEINSTANCE(i) | DIDFT_OPTIONAL, 0}
+#define MAKE_BUTTON(i) \
+  {&GUID_Button, FIELD_OFFSET(JoyData, buttons) + i, \
+   DIDFT_BUTTON | DIDFT_MAKEINSTANCE(i) | DIDFT_OPTIONAL, 0}
+#define MAKE_POV() \
+  {&GUID_POV, FIELD_OFFSET(JoyData, pov), DIDFT_POV | DIDFT_OPTIONAL, 0}
+  DIOBJECTDATAFORMAT rgodf[] = {
+    MAKE_AXIS(0),
+    MAKE_AXIS(1),
+    MAKE_AXIS(2),
+    MAKE_AXIS(3),
+    MAKE_AXIS(4),
+    MAKE_AXIS(5),
+    MAKE_AXIS(6),
+    MAKE_AXIS(7),
+    MAKE_AXIS(8),
+    MAKE_AXIS(9),
+    MAKE_BUTTON(0),
+    MAKE_BUTTON(1),
+    MAKE_BUTTON(2),
+    MAKE_BUTTON(3),
+    MAKE_BUTTON(4),
+    MAKE_BUTTON(5),
+    MAKE_BUTTON(6),
+    MAKE_BUTTON(7),
+    MAKE_BUTTON(8),
+    MAKE_BUTTON(9),
+    MAKE_BUTTON(10),
+    MAKE_BUTTON(11),
+    MAKE_BUTTON(12),
+    MAKE_BUTTON(13),
+    MAKE_BUTTON(14),
+    MAKE_BUTTON(15),
+    MAKE_BUTTON(16),
+    MAKE_POV(),
+  };
+#undef MAKE_AXIS
+#undef MAKE_BUTTON
+#undef MAKE_POV
+
+  DIDATAFORMAT df = {
+    sizeof (DIDATAFORMAT),
+    sizeof (DIOBJECTDATAFORMAT),
+    DIDF_ABSAXIS,
+    sizeof (JoyData),
+    sizeof (rgodf) / sizeof (rgodf[0]),
+    rgodf
+  };
+
+  // If we can't set the data format on the device, don't add it to our
+  // list, since we won't know how to read data from it.
+  if (FAILED(gamepad->SetDataFormat(&df))) {
+    gamepad->Release();
+    return DIENUM_CONTINUE;
+  }
+
+  InternalDirectInputDevice device;
+  device.guid = instance->guidInstance;
+  device.gamepad = gamepad;
+  std::string vendor;
+  std::string product;
+  if (!GetDirectInputVendorProduct(gamepad, &vendor, &product)) {
+    gamepad->Release();
+    return DIENUM_CONTINUE;
+  }
+
+  // Set the dead zone to 10% of the axis length for all axes. This
+  // gives us a larger space for what's "neutral" so the controls don't
+  // slowly drift.
+  SetDirectInputDeadZone(gamepad, 1000);
+  device.mapper = GetGamepadStandardMappingFunction(vendor, product);
+  if (device.mapper) {
+    base::swprintf(device.id,
+                   WebGamepad::idLengthCap,
+                   L"STANDARD GAMEPAD (%ls)",
+                   instance->tszProductName);
+    ctxt->directinput_devices->push_back(device);
+  } else {
+    gamepad->Release();
+  }
+  return DIENUM_CONTINUE;
+}
+
 }  // namespace
 
 GamepadPlatformDataFetcherWin::GamepadPlatformDataFetcherWin()
     : xinput_dll_(FilePath(FILE_PATH_LITERAL("xinput1_3.dll"))),
-      xinput_available_(GetXinputDllFunctions()) {
+      xinput_available_(GetXInputDllFunctions()) {
+  directinput_available_ =
+      SUCCEEDED(DirectInput8Create(GetModuleHandle(NULL),
+                                   DIRECTINPUT_VERSION,
+                                   IID_IDirectInput8,
+                                   (void **)&directinput_interface_,

[scottmg, 2013/02/19 18:50:52]

reinterpret_cast<void**>(...)

[teravest, 2013/02/19 20:53:37]

Done.

+                                   NULL));
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i)
+    pad_state_[i].status = DISCONNECTED;
 }
 
 GamepadPlatformDataFetcherWin::~GamepadPlatformDataFetcherWin() {
-}
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    if (pad_state_[i].status == DIRECTINPUT_CONNECTED)
+      pad_state_[i].directinput_gamepad->Release();
+  }
+}
+
+int GamepadPlatformDataFetcherWin::FirstAvailableGamepadId() const {
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    if (pad_state_[i].status == DISCONNECTED)
+      return i;
+  }
+  return -1;
+}
+
+bool GamepadPlatformDataFetcherWin::HasXInputGamepad(int index) const {
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    if (pad_state_[i].status == XINPUT_CONNECTED &&
+        pad_state_[i].xinput_index == index)
+      return true;
+  }
+  return false;
+}
+
+bool GamepadPlatformDataFetcherWin::HasDirectInputGamepad(
+    const GUID &guid) const {

[scottmg, 2013/02/19 18:50:52]

nit; GUID&

+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    if (pad_state_[i].status == DIRECTINPUT_CONNECTED &&
+        pad_state_[i].guid == guid)
+      return true;
+  }
+  return false;
+}
+
+void GamepadPlatformDataFetcherWin::EnumerateDevices(
+    WebGamepads* pads) {
+  TRACE_EVENT0("GAMEPAD", "EnumerateDevices");
+
+  // Mark all disconnected pads DISCONNECTED.
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    if (!pads->items[i].connected)
+      pad_state_[i].status = DISCONNECTED;
+  }
+
+  for (size_t i = 0; i <= XUSER_MAX_COUNT; ++i) {
+    if (HasXInputGamepad(i))
+      continue;
+    int pad_index = FirstAvailableGamepadId();
+    if (pad_index == -1)
+      return;  // We can't add any more gamepads.
+    WebGamepad &pad = pads->items[pad_index];

[scottmg, 2013/02/19 18:50:52]

nit; WebGamepad&

[teravest, 2013/02/19 20:53:37]

Done.

+    if (xinput_available_ && GetXInputPadConnectivity(i, &pad)) {
+      pad_state_[pad_index].status = XINPUT_CONNECTED;
+      pad_state_[pad_index].xinput_index = i;
+    }
+  }
+
+  if (directinput_available_) {
+    struct EnumDevicesContext context;
+    std::vector<InternalDirectInputDevice> directinput_gamepads;
+    context.directinput_interface = directinput_interface_;
+    context.directinput_devices = &directinput_gamepads;
+
+    directinput_interface_->EnumDevices(
+        DI8DEVCLASS_GAMECTRL,
+        &DirectInputEnumDevicesCallback,
+        &context,
+        DIEDFL_ATTACHEDONLY);
+    for (size_t i = 0; i < directinput_gamepads.size(); ++i) {
+      if (HasDirectInputGamepad(directinput_gamepads[i].guid)) {
+        directinput_gamepads[i].gamepad->Release();
+        continue;
+      }
+      int pad_index = FirstAvailableGamepadId();
+      if (pad_index == -1)
+        return;
+      WebGamepad &pad = pads->items[pad_index];

[scottmg, 2013/02/19 18:50:52]

nit; WebGamepad&

[teravest, 2013/02/19 20:53:37]

Done.

+      pad.connected = true;
+      wcscpy_s(pad.id, WebGamepad::idLengthCap, directinput_gamepads[i].id);
+      PadState &state = pad_state_[pad_index];

[scottmg, 2013/02/19 18:50:52]

nit; PadState&

[teravest, 2013/02/19 20:53:37]

Done.

+      state.status = DIRECTINPUT_CONNECTED;
+      state.guid = directinput_gamepads[i].guid;
+      state.directinput_gamepad = directinput_gamepads[i].gamepad;
+      state.mapper = directinput_gamepads[i].mapper;
+    }
+  }
+}
+
 
 void GamepadPlatformDataFetcherWin::GetGamepadData(WebGamepads* pads,
-                                        bool devices_changed_hint) {
+                                                   bool devices_changed_hint) {
   TRACE_EVENT0("GAMEPAD", "GetGamepadData");
 
-  // If there's no XInput DLL on the system, early out so that we don't
-  // call any other XInput functions.
-  if (!xinput_available_) {
+  if (!xinput_available_ && !directinput_available_) {
     pads->length = 0;
     return;
   }
 
-  pads->length = WebGamepads::itemsLengthCap;
-
+  // A note on XInput devices:
   // If we got notification that system devices have been updated, then
   // run GetCapabilities to update the connected status and the device
   // identifier. It can be slow to do to both GetCapabilities and
   // GetState on unconnected devices, so we want to avoid a 2-5ms pause
   // here by only doing this when the devices are updated (despite
   // documentation claiming it's OK to call it any time).
-  if (devices_changed_hint) {
-    for (unsigned i = 0; i < WebGamepads::itemsLengthCap; ++i) {
-      WebGamepad& pad = pads->items[i];
-      TRACE_EVENT1("GAMEPAD", "GetCapabilities", "id", i);
-      XINPUT_CAPABILITIES caps;
-      DWORD res = xinput_get_capabilities_(i, XINPUT_FLAG_GAMEPAD, &caps);
-      if (res == ERROR_DEVICE_NOT_CONNECTED) {
-        pad.connected = false;
-      } else {
-        pad.connected = true;
-        base::swprintf(pad.id,
-                       WebGamepad::idLengthCap,
-                       L"Xbox 360 Controller (XInput STANDARD %ls)",
-                       GamepadSubTypeName(caps.SubType));
-      }
+  if (devices_changed_hint)
+    EnumerateDevices(pads);
+
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    WebGamepad& pad = pads->items[i];
+    if (pad_state_[i].status == XINPUT_CONNECTED)
+      GetXInputPadData(i, &pad);
+    else if (pad_state_[i].status == DIRECTINPUT_CONNECTED)
+      GetDirectInputPadData(i, &pad);
+  }
+  pads->length = WebGamepads::itemsLengthCap;
+}
+
+bool GamepadPlatformDataFetcherWin::GetXInputPadConnectivity(
+    int i,
+    WebGamepad* pad) const {
+  DCHECK(pad);
+  TRACE_EVENT1("GAMEPAD", "GetXInputPadConnectivity", "id", i);
+  XINPUT_CAPABILITIES caps;
+  DWORD res = xinput_get_capabilities_(i, XINPUT_FLAG_GAMEPAD, &caps);
+  if (res == ERROR_DEVICE_NOT_CONNECTED ||
+      caps.SubType != kDeviceSubTypeGamepad) {
+    pad->connected = false;
+    return false;
+  } else {
+    pad->connected = true;
+    base::swprintf(pad->id,
+                   WebGamepad::idLengthCap,
+                   L"Xbox 360 Controller (XInput STANDARD %ls)",
+                   GamepadSubTypeName(caps.SubType));
+    return true;
+  }
+}
+
+void GamepadPlatformDataFetcherWin::GetXInputPadData(
+    int i,
+    WebGamepad* pad) {
+  // We rely on device_changed and GetCapabilities to tell us that
+  // something's been connected, but we will mark as disconnected if
+  // GetState returns that we've lost the pad.
+  if (!pad->connected)
+    return;
+
+  XINPUT_STATE state;
+  memset(&state, 0, sizeof(XINPUT_STATE));
+  TRACE_EVENT_BEGIN1("GAMEPAD", "XInputGetState", "id", i);
+  DWORD dwResult = xinput_get_state_(pad_state_[i].xinput_index, &state);
+  TRACE_EVENT_END1("GAMEPAD", "XInputGetState", "id", i);
+
+  if (dwResult == ERROR_SUCCESS) {
+    pad->timestamp = state.dwPacketNumber;
+    pad->buttonsLength = 0;
+#define ADD(b) pad->buttons[pad->buttonsLength++] = \
+  ((state.Gamepad.wButtons & (b)) ? 1.0 : 0.0);
+    ADD(XINPUT_GAMEPAD_A);
+    ADD(XINPUT_GAMEPAD_B);
+    ADD(XINPUT_GAMEPAD_X);
+    ADD(XINPUT_GAMEPAD_Y);
+    ADD(XINPUT_GAMEPAD_LEFT_SHOULDER);
+    ADD(XINPUT_GAMEPAD_RIGHT_SHOULDER);
+    pad->buttons[pad->buttonsLength++] = state.Gamepad.bLeftTrigger / 255.0;
+    pad->buttons[pad->buttonsLength++] = state.Gamepad.bRightTrigger / 255.0;
+    ADD(XINPUT_GAMEPAD_BACK);
+    ADD(XINPUT_GAMEPAD_START);
+    ADD(XINPUT_GAMEPAD_LEFT_THUMB);
+    ADD(XINPUT_GAMEPAD_RIGHT_THUMB);
+    ADD(XINPUT_GAMEPAD_DPAD_UP);
+    ADD(XINPUT_GAMEPAD_DPAD_DOWN);
+    ADD(XINPUT_GAMEPAD_DPAD_LEFT);
+    ADD(XINPUT_GAMEPAD_DPAD_RIGHT);
+#undef ADD
+    pad->axesLength = 0;
+    // XInput are +up/+right, -down/-left, we want -up/-left.
+    pad->axes[pad->axesLength++] = NormalizeXInputAxis(state.Gamepad.sThumbLX);
+    pad->axes[pad->axesLength++] = -NormalizeXInputAxis(state.Gamepad.sThumbLY);
+    pad->axes[pad->axesLength++] = NormalizeXInputAxis(state.Gamepad.sThumbRX);
+    pad->axes[pad->axesLength++] = -NormalizeXInputAxis(state.Gamepad.sThumbRY);
+  } else {
+    pad->connected = false;
+  }
+}
+
+void GamepadPlatformDataFetcherWin::GetDirectInputPadData(
+    int index,
+    WebGamepad* pad) {
+  if (!pad->connected)
+    return;
+
+  IDirectInputDevice8* gamepad = pad_state_[index].directinput_gamepad;
+  if (FAILED(gamepad->Poll())) {
+    // Polling didn't work, try acquiring the gamepad.
+    if (FAILED(gamepad->Acquire())) {
+      pad->buttonsLength = 0;
+      pad->axesLength = 0;
+      return;
     }
-  }
-
-  // We've updated the connection state if necessary, now update the actual
-  // data for the devices that are connected.
-  for (unsigned i = 0; i < WebGamepads::itemsLengthCap; ++i) {
-    WebGamepad& pad = pads->items[i];
-
-    // We rely on device_changed and GetCapabilities to tell us that
-    // something's been connected, but we will mark as disconnected if
-    // GetState returns that we've lost the pad.
-    if (!pad.connected)
-      continue;
-
-    XINPUT_STATE state;
-    memset(&state, 0, sizeof(XINPUT_STATE));
-    TRACE_EVENT_BEGIN1("GAMEPAD", "XInputGetState", "id", i);
-    DWORD dwResult = xinput_get_state_(i, &state);
-    TRACE_EVENT_END1("GAMEPAD", "XInputGetState", "id", i);
-
-    if (dwResult == ERROR_SUCCESS) {
-      pad.timestamp = state.dwPacketNumber;
-      pad.buttonsLength = 0;
-#define ADD(b) pad.buttons[pad.buttonsLength++] = \
-    ((state.Gamepad.wButtons & (b)) ? 1.0 : 0.0);
-      ADD(XINPUT_GAMEPAD_A);
-      ADD(XINPUT_GAMEPAD_B);
-      ADD(XINPUT_GAMEPAD_X);
-      ADD(XINPUT_GAMEPAD_Y);
-      ADD(XINPUT_GAMEPAD_LEFT_SHOULDER);
-      ADD(XINPUT_GAMEPAD_RIGHT_SHOULDER);
-      pad.buttons[pad.buttonsLength++] = state.Gamepad.bLeftTrigger / 255.0;
-      pad.buttons[pad.buttonsLength++] = state.Gamepad.bRightTrigger / 255.0;
-      ADD(XINPUT_GAMEPAD_BACK);
-      ADD(XINPUT_GAMEPAD_START);
-      ADD(XINPUT_GAMEPAD_LEFT_THUMB);
-      ADD(XINPUT_GAMEPAD_RIGHT_THUMB);
-      ADD(XINPUT_GAMEPAD_DPAD_UP);
-      ADD(XINPUT_GAMEPAD_DPAD_DOWN);
-      ADD(XINPUT_GAMEPAD_DPAD_LEFT);
-      ADD(XINPUT_GAMEPAD_DPAD_RIGHT);
-#undef ADD
-      pad.axesLength = 0;
-      // XInput are +up/+right, -down/-left, we want -up/-left.
-      pad.axes[pad.axesLength++] = NormalizeAxis(state.Gamepad.sThumbLX);
-      pad.axes[pad.axesLength++] = -NormalizeAxis(state.Gamepad.sThumbLY);
-      pad.axes[pad.axesLength++] = NormalizeAxis(state.Gamepad.sThumbRX);
-      pad.axes[pad.axesLength++] = -NormalizeAxis(state.Gamepad.sThumbRY);
-    } else {
-      pad.connected = false;
+    // Try polling again.
+    if (FAILED(gamepad->Poll())) {
+      pad->buttonsLength = 0;
+      pad->axesLength = 0;
+      return;
     }
   }
-}
-
-bool GamepadPlatformDataFetcherWin::GetXinputDllFunctions() {
+  JoyData state;
+  if (FAILED(gamepad->GetDeviceState(sizeof(JoyData), &state))) {
+    pad->connected = false;
+    return;
+  }
+
+  WebGamepad raw;
+  raw.connected = true;
+  for (int i = 0; i < 16; i++)
+    raw.buttons[i] = (state.buttons[i] & 0x80) ? 1.0 : 0.0;
+
+  // We map the POV (often a D-pad) into the buttons 16-19.
+  // DirectInput gives pov measurements in hundredths of degrees,
+  // clockwise from "North".
+  // We use 22.5 degree slices so we can handle diagonal D-raw presses.
+  static const int arc_segment = 2250;  // 22.5 degrees = 1/16 circle
+  if (state.pov > arc_segment && state.pov < 7 * arc_segment)
+    raw.buttons[19] = 1.0;
+  else
+    raw.buttons[19] = 0.0;
+
+  if (state.pov > 5 * arc_segment && state.pov < 11 * arc_segment)
+    raw.buttons[17] = 1.0;
+  else
+    raw.buttons[17] = 0.0;
+
+  if (state.pov > 9 * arc_segment && state.pov < 15 * arc_segment)
+    raw.buttons[18] = 1.0;
+  else
+    raw.buttons[18] = 0.0;
+
+  if (state.pov < 3 * arc_segment ||
+      (state.pov > 13 * arc_segment && state.pov < 36000))
+    raw.buttons[16] = 1.0;
+  else
+    raw.buttons[16] = 0.0;
+
+  for (int i = 0; i < 10; i++)
+    raw.axes[i] = state.axes[i];
+  pad_state_[index].mapper(raw, pad);
+}
+
+bool GamepadPlatformDataFetcherWin::GetXInputDllFunctions() {
   xinput_get_capabilities_ = NULL;
   xinput_get_state_ = NULL;
   xinput_enable_ = static_cast<XInputEnableFunc>(
       xinput_dll_.GetFunctionPointer("XInputEnable"));
   if (!xinput_enable_)
     return false;
   xinput_get_capabilities_ = static_cast<XInputGetCapabilitiesFunc>(
       xinput_dll_.GetFunctionPointer("XInputGetCapabilities"));
   if (!xinput_get_capabilities_)
     return false;
   xinput_get_state_ = static_cast<XInputGetStateFunc>(
       xinput_dll_.GetFunctionPointer("XInputGetState"));
   if (!xinput_get_state_)
     return false;
   xinput_enable_(true);
   return true;
 }
 
 }  // namespace content