Thu
21
Mar 2013

When you connect second USB mouse to your computer, you don't have second cursor to move on the screen and click on things. Instead you can move and click the single cursor with both mice. What if you want to distinguish messages from multiple mice in your program? I found the solution here. I downloaded and looked at the source code of MouseParty.zip linked from this page.

Handling multiple mice is possible using part of WinAPI called Raw Input. If you have <Windows.h> included, have your WinAPI window and message loop, you only need to initialize Raw Input like this:

RAWINPUTDEVICE device;
device.usUsagePage = 0x01;
device.usUsage = 0x02;
device.dwFlags = 0;
device.hwndTarget = 0;
RegisterRawInputDevices(&device, 1, sizeof device);

You then start to receive WM_INPUT message, which should be handled this way:

case WM_INPUT:
  OnRawInput(
    GET_RAWINPUT_CODE_WPARAM(wParam) == RIM_INPUT,
    (HRAWINPUT)lParam);
  // Must call DefWindowProc!
  break;

Where OnRawInput is my function:

std::vector<char> m_RawInputMessageData; // Buffer

void OnRawInput(bool inForeground, HRAWINPUT hRawInput)
{
    UINT dataSize;
    GetRawInputData(
      hRawInput, RID_INPUT, NULL, &dataSize, sizeof(RAWINPUTHEADER));

    if(dataSize == 0)
      return;
    if(dataSize > m_RawInputMessageData.size())
        m_RawInputMessageData.resize(dataSize);

    void* dataBuf = &m_RawInputMessageData[0];
    GetRawInputData(
      hRawInput, RID_INPUT, dataBuf, &dataSize, sizeof(RAWINPUTHEADER));

    const RAWINPUT *raw = (const RAWINPUT*)dataBuf;
    if (raw->header.dwType == RIM_TYPEMOUSE)
    {
        HANDLE deviceHandle = raw->header.hDevice;

        const RAWMOUSE& mouseData = raw->data.mouse;

        USHORT flags = mouseData.usButtonFlags;
        short wheelDelta = (short)mouseData.usButtonData;
        LONG x = mouseData.lLastX, y = mouseData.lLastY;

        wprintf(
            L"Mouse: Device=0x%08X, Flags=%04x, WheelDelta=%d, X=%d, Y=%d\n",
            deviceHandle, flags, wheelDelta, x, y);
    }
}

• deviceHandle is a handle that lets you distinguish which mouse generated this event.
• flags is the main type of event. It may be zero or more of following flags:
  RI_MOUSE_LEFT_BUTTON_DOWN
  RI_MOUSE_LEFT_BUTTON_UP
  RI_MOUSE_MIDDLE_BUTTON_DOWN
  RI_MOUSE_MIDDLE_BUTTON_UP
  RI_MOUSE_RIGHT_BUTTON_DOWN
  RI_MOUSE_RIGHT_BUTTON_UP
  RI_MOUSE_BUTTON_1_DOWN
  RI_MOUSE_BUTTON_1_UP
  RI_MOUSE_BUTTON_2_DOWN
  RI_MOUSE_BUTTON_2_UP
  RI_MOUSE_BUTTON_3_DOWN
  RI_MOUSE_BUTTON_3_UP
  RI_MOUSE_BUTTON_4_DOWN
  RI_MOUSE_BUTTON_4_UP
  RI_MOUSE_BUTTON_5_DOWN
  RI_MOUSE_BUTTON_5_UP
  RI_MOUSE_WHEEL
• wheelDelta, applicable when RI_MOUSE_WHEEL is set, gives positive or negative delta of mouse wheel. On my system it's always -120 or +120.
• x, y is relative or absolute, depending on the (mouseData.usFlags & MOUSE_MOVE_ABSOLUTE). But in my tests it's always relative, like (-3, 0), on every USB mouse, as well as touchpad on my laptop.
• There is also mouseData.ulRawButtons available with bits corresponding to current state of all mouse buttons, but works on my PC and not on my laptop (it is always 0).

Mouse: Device=0x0001003D, Flags=0001, WheelDelta=0, X=0, Y=0
Mouse: Device=0x0001003D, Flags=0002, WheelDelta=0, X=0, Y=0
Mouse: Device=0x0001003D, Flags=0000, WheelDelta=0, X=-1, Y=0
Mouse: Device=0x0001003D, Flags=0004, WheelDelta=0, X=0, Y=0
Mouse: Device=0x0001003D, Flags=0008, WheelDelta=0, X=0, Y=0
Mouse: Device=0x0001003D, Flags=0400, WheelDelta=120, X=0, Y=0
Mouse: Device=0x0001003D, Flags=0400, WheelDelta=-120, X=0, Y=0
Mouse: Device=0x0001003D, Flags=0000, WheelDelta=0, X=1, Y=0
Mouse: Device=0x0001003D, Flags=0000, WheelDelta=0, X=1, Y=0
Mouse: Device=0x0001003D, Flags=0000, WheelDelta=0, X=2, Y=-1
Mouse: Device=0x0001003D, Flags=0000, WheelDelta=0, X=1, Y=-1

If you want to know in advance what mice are available in the system, you can enumerate them with following code:

UINT numDevices;
GetRawInputDeviceList(
  NULL, &numDevices, sizeof(RAWINPUTDEVICELIST));
if(numDevices == 0) return;

std::vector<RAWINPUTDEVICELIST> deviceList(numDevices);
GetRawInputDeviceList(
  &deviceList[0], &numDevices, sizeof(RAWINPUTDEVICELIST));

std::vector<wchar_t> deviceNameData;
wstring deviceName;
for(UINT i = 0; i < numDevices; ++i)
{
  const RAWINPUTDEVICELIST& device = deviceList[i];
  if(device.dwType == RIM_TYPEMOUSE)
  {
    wprintf(L"Mouse: Handle=0x%08X\n", device.hDevice);

    UINT dataSize;
    GetRawInputDeviceInfo(
      device.hDevice, RIDI_DEVICENAME, nullptr, &dataSize);
    if(dataSize)
    {
      deviceNameData.resize(dataSize);
      UINT result = GetRawInputDeviceInfo(
        device.hDevice, RIDI_DEVICENAME, &deviceNameData[0], &dataSize);
      if(result != UINT_MAX)
      {
        deviceName.assign(deviceNameData.begin(), deviceNameData.end());
        wprintf(L"  Name=%s\n", deviceName.c_str());
      }
    }

    RID_DEVICE_INFO deviceInfo;
    deviceInfo.cbSize = sizeof deviceInfo;
    dataSize = sizeof deviceInfo;
    UINT result = GetRawInputDeviceInfo(
      device.hDevice, RIDI_DEVICEINFO, &deviceInfo, &dataSize);
    if(result != UINT_MAX)
    {
      assert(deviceInfo.dwType == RIM_TYPEMOUSE);
      wprintf(
        L"  Id=%u, Buttons=%u, SampleRate=%u, HorizontalWheel=%s\n",
        deviceInfo.mouse.dwId,
        deviceInfo.mouse.dwNumberOfButtons,
        deviceInfo.mouse.dwSampleRate,
        deviceInfo.mouse.fHasHorizontalWheel ? L"1" : L"0");
    }
  }
}

But the system on my PC reports 3 mouse devices even when I have only one USB mouse connected. Names are also quite cryptic. So it's not very useful I think.

Mouse: Handle=0x0001003F
  Name=\\?\Root#RDP_MOU#0000#{378de44c-56ef-11d1-bc8c-00a0c91405dd}
  Id=2, Buttons=2, SampleRate=60, HorizontalWheel=0
Mouse: Handle=0x0001003D
  Name=\\?\HID#VID_09DA&PID_000E#6&2ff89cff&0&0000#{378de44c-56ef-11d1-bc8c-00a0c91405dd}
  Id=256, Buttons=5, SampleRate=100, HorizontalWheel=0
Mouse: Handle=0x0001003B
  Name=\\?\HID#VID_062A&PID_0201&MI_01&Col01#7&136f4655&0&0000#{378de44c-56ef-11d1-bc8c-00a0c91405dd}
  Id=256, Buttons=0, SampleRate=0, HorizontalWheel=0

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