SendInput to background window

3
votes

I want to send the mouse and keyboard input, which is recieved from android client, to games running on windows. SendInput works for almost all games I have worked so far. But for SendInput to work the game must be a foreground window.

To solve that I used PostMessage(hwnd,...) with hwnd being handle to the game window. But this does not work if game is using DirectInput. That was solved by hooking GetDeviceState. Now another game I started working on is using WM_INPUT or raw input and I have to create raw input to make it work.

According to this MSDN Article

DirectInput is a set of API calls that abstracts input devices on the system. Internally, DirectInput creates a second thread to read WM_INPUT data, and using the DirectInput APIs will add more overhead than simply reading WM_INPUT directly.

directInput works using WM_INPUT.

The SendInput function inserts the events in the INPUT structures serially into the keyboard or mouse input stream. These events are not interspersed with other keyboard or mouse input events inserted either by the user (with the keyboard or mouse) or by calls to keybd_event, mouse_event, or other calls to SendInput.

So SendInput is also providing abstraction.

All I want is to send the input to application independently even when its window is not in focus. That way I will be able to send input to multiple games at once. Is there any way to achieve this using one higher level API call like SendInput? Can this be done with SendInput? Is there any C/C++ library for that?

1
c++winapisdlsendinputdirectinput
Games do a lot to try and prevent this, for obvious reasons. I'd consider using an arduino board to mimic a keyboard. – Matt
@Matt SendInput alone works fine with only drawback that it works on the focused window only. – SMUsamaShah
If you take a look at the parameters to SendInput, it should be immediately obvious, that you cannot control, where the input goes. There is no higher level API to make this work, and PostMessage is the epitome of wrong. Reason for downvote: You have been the 100,000th member to ask this question, in other words: it "does not show research effort". – IInspectable
There isn't, and all other questions have been answered to this end. Keeping asking for something, that doesn't have a solution, is like trying to lose weight by weighing more often. – IInspectable
See "You can’t simulate keyboard input with PostMessage", and "When something gets added to a queue, it takes time for it to come out the front of the queue" – Remy Lebeau

1 Answers

5
votes

When registering your input device using the RAWINPUTDEVICE structure, set dwFlags = RIDEV_EXINPUTSINK to receive input when the process is in the background.

Example:

RAWINPUTDEVICE rid;

rid.usUsagePage = 1;
rid.usUsage     = 4;    // Joystick
rid.dwFlags     = RIDEV_EXINPUTSINK;
rid.hwndTarget  = window;

if (!RegisterRawInputDevices(&rid, 1, sizeof(RAWINPUTDEVICE)))
    return -1;