Simulating Raw Input on Windows

Question

I have an application that does some complicated things with raw input and I would like to have some automated tests for it. This is the code that sends input albeit chopped down a bit to make it easier to follow.

Sending:

GetRawInputDeviceList(nullptr, &numDevices, sizeof(RAWINPUTDEVICELIST));
rawInputDeviceList = new RAWINPUTDEVICELIST[numDevices];
GetRawInputDeviceList(rawInputDeviceList, &numDevices, sizeof(RAWINPUTDEVICELIST));

HGLOBAL hRaw = ::GlobalAlloc(GHND, sizeof(RAWINPUT));
RAWINPUT *pRaw = reinterpret_cast<RAWINPUT*>(::GlobalLock(hRaw));
pRaw->data.keyboard.MakeCode = 30;
pRaw->data.keyboard.Flags = 0;
pRaw->data.keyboard.Reserved = 0;
pRaw->data.keyboard.VKey = 0x43;
pRaw->data.keyboard.Message = WM_KEYDOWN;
pRaw->data.keyboard.ExtraInformation = 0;
pRaw->header.dwType = RIM_TYPEKEYBOARD;
pRaw->header.dwSize = sizeof(RAWINPUT);
pRaw->header.hDevice = rawInputDeviceList[0].hDevice;
pRaw->header.wParam = (WPARAM)RIM_INPUT;
::GlobalUnlock(hRaw);

SendMessage(hWnd_, WM_INPUT, (WPARAM)RIM_INPUT, (LPARAM)hRaw);

Receiving:

case WM_INPUT:
  UINT size = 0;  
  if(GetRawInputData((HRAWINPUT)lParam, RID_INPUT, NULL, &size, sizeof(RAWINPUTHEADER)))
    return GetLastError();

The return value from GetLastError() is ERROR_INVALID_HANDLE(6). However I can read the handle fine if I use GlobalLock it myself.

According to http://msdn.microsoft.com/en-us/library/windows/desktop/ms645596(v=vs.85).aspx "lParam: A handle to the RAWINPUT structure. This comes from the lParam in WM_INPUT."

I've tried just using a pointer and I get the same error message. I've tried with/without unlocking, as well as using LocalAlloc/LocalLock instead. I've tried with PostMessage and it's all the same result, and I am now out of ideas.

Answer 1

The WM_INPUT message cannot be sent between processes. Like WM_PAINT, it is a synthesized message which can only be properly generated by the system itself. The lParam is not just an HGLOBAL containing the data, it is an opaque handle understood only by the raw input code.

Raw Input messages are generated directly by the GetMessage/PeekMessage internals, and the associated objects are cleaned up by DefWindowProc. SendMessage will not marshal the LPARAM for WM_INPUT, because the code to do so wasn't written as it is not intended to be used in that way.