CODEWITHSUNDEEP
windowswinapic++-cliraw-input
william baker
william baker

Reputation: 31

Trouble catching WM_INPUT message for lParam, to collect Raw Mouse Input

For my college project I am developing a solution to distinguish between mouse user data from a person with Parkinson's compared to a healthy person. For which I need mouse data, ideally raw.

I presume I have misunderstood how to collect raw mouse input from the WM_INPUT message but I cannot figure it out.

I have been looking at the following thread: How to accurately measure mouse movement in inches or centimetres for a mouse with a known DPI and Mouse input libraries on github all of which seem to easily catch a WM_INPUT message whose lParam is a handle to some RawInputData with something like this:

GetMessage(&msg, GetActiveWindow(), WM_INPUT, 0);
if (msg.message == WM_INPUT){  .....

And then retreiving the lParam from the message and collecting the data associated with that handle with:

GetRawInputData((HRAWINPUT)lParam, RID_INPUT, lpb, &dwSize, sizeof(RAWINPUTHEADER));

However when I call GetMessage in my main loop, the function never exits! Consequently there is no way (that i know of) for me to get a handle to the RawInputData. Especially since the MSDN page just assumes you have the lParam already.

In summary I need a method of getting an lParam to pass to the GetRawInputData function which will remain active whether the program is running in the active window of not.

I'm running this code in a blank C++ CLR project in Visual Studio with the "winuser.h" library.

#include "stdafx.h"
#include "Windows.h"
#include "winuser.h"

#ifndef HID_USAGE_PAGE_GENERIC
#define HID_USAGE_PAGE_GENERIC         ((USHORT) 0x01)
#endif
#ifndef HID_USAGE_GENERIC_MOUSE
#define HID_USAGE_GENERIC_MOUSE        ((USHORT) 0x02)
#endif

int main(array<System::String ^> ^args)
{
    RAWINPUTDEVICE Rid[1];
    Rid[0].usUsagePage = HID_USAGE_PAGE_GENERIC;
    Rid[0].usUsage = HID_USAGE_GENERIC_MOUSE;
    Rid[0].dwFlags = 0; //ideally RIDEV_INPUTSINK but that prevents registration
    Rid[0].hwndTarget = GetActiveWindow(); //ideally this would be Null to be independent of the active window

    if (RegisterRawInputDevices(Rid, 1, sizeof(Rid[0])) == FALSE) {
        //registration failed. Call GetLastError for the cause of the error
        Console::WriteLine("Registration Error");
    }
    MSG msg;

    while (true) {
        while (GetMessage(&msg, GetActiveWindow(), WM_INPUT, 0) != 0) { //this command is never completed
            DispatchMessage(&msg); //this line is never ran
        }
        if (msg.message == WM_INPUT) {
            Console::WriteLine("caught a message!!!");
        }

    }
}

Upvotes: 0

Views: 2266

Answers (1)

william baker
william baker

Reputation: 31

Issue solved after much more research I found the winAPI walk through which I followed fixing the issue above by adding an: int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE unused, PSTR cmd, int show) {.....} Function to register devices and create a window then call GetMessage which calls LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) {....} with the parameters occupied by the message ID,WParam and LParam corresponding the message event. For anyone stuck with a similar issue follow this MSDN guide: https://msdn.microsoft.com/en-us/library/bb384843.aspx

Upvotes: 1

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