CODEWITHSUNDEEP
mousemouseeventraw-input
Raj
Raj

Reputation: 795

Mouse Position from Raw Input method

I am trying to get mouse position by using Raw input method. In the RAWMOUSE structure am always getting value MOUSE_MOVE_RELATIVE as usFlags that means am getting relative value of last mouse position. but i want absolute position of mouse. how to get absolute position value of mouse from Raw input ?

Upvotes: 3

Views: 2857

Answers (2)

DJm00n
DJm00n

Reputation: 1441

RAWMOUSE have exact same values that Windows received from mouse hardware (it could be HID USB/Bluetooth or i8042 PS/2 mouse etc). Usually mouses are sending relative movement, but some could send absolute - for example touch screens, RDP mouse (yay!).

So if you need absolute mouse pos (for example for game menu) you can use GetCursorPos API to get coords of Windows-rendered cursor on the screen.

But its not the same thing as sent with MOUSE_MOVE_ABSOLUTE flag in RAWMOUSE.

MOUSE_MOVE_ABSOLUTE is mouse movement in 0..65535 range in device-space, not screen-space. Here is some code how to convert it to screen-space:

if (mouse.usFlags & MOUSE_MOVE_ABSOLUTE)
{
    RECT rect;
    if (mouse.usFlags & MOUSE_VIRTUAL_DESKTOP)
    {
        rect.left = GetSystemMetrics(SM_XVIRTUALSCREEN);
        rect.top = GetSystemMetrics(SM_YVIRTUALSCREEN);
        rect.right = GetSystemMetrics(SM_CXVIRTUALSCREEN);
        rect.bottom = GetSystemMetrics(SM_CYVIRTUALSCREEN);
    }
    else
    {
        rect.left = 0;
        rect.top = 0;
        rect.right = GetSystemMetrics(SM_CXSCREEN);
        rect.bottom = GetSystemMetrics(SM_CYSCREEN);
    }

    int absoluteX = MulDiv(mouse.lLastX, rect.right, USHRT_MAX) + rect.left;
    int absoluteY = MulDiv(mouse.lLastY, rect.bottom, USHRT_MAX) + rect.top;
    ...
}
else if (mouse.lLastX != 0 || mouse.lLastY != 0)
{
    int relativeX = mouse.lLastX;
    int relativeY = mouse.lLastY;
    ...
}
...

Bonus: here is info on the virtual screen MOUSE_VIRTUAL_DESKTOP flag.

Upvotes: 3

Shawn A. Van Ness
Shawn A. Van Ness

Reputation: 71

[Weird to see a 9 year old unanswered question as a top google search result, so I'll offer an answer.. better late than never!]

At the level of Raw Input API, you are getting the raw horizontal/vertical movement of the mouse device -- what the mouse reports at the hardware level.

According to the docs (I haven't verified) these delta X/Y values are not yet processed by the desktop mouse speed/acceleration/slowdown settings. So even if you started tracking the deltas from a known absolute location, you would quickly drift away from where Windows is positioning the mouse cursor, on-screen.

What's not clear from the docs, is what units or scale these relative X/Y values are reported in. It would be nice if it were somehow normalized, but I suspect it depends on the DPI resolution of your mouse. (I will find a mouse with adjustable DPI to test, and report back, if no one edits me first.)

Edit/Update: I got my hands on a mouse with adjustable DPI .. did some crude testing, enough to confirm the rough scale of the lLastX/Y values seems to match the hardware DPI.. eg. with the mouse in 1200 dpi mode, moving it physically 1 inch from left to right, generates a net sum of lLastX values ~= 1200.

Upvotes: 3

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