Simulating Keyboard Input to Another Program w/o Messages

Posted on 2000-03-06
Last Modified: 2013-12-03
I'm interested in automating the process of logging into a game by simulating keystrokes from the user.

Once the game has started, I can simulate keystrokes with SendMessage or PostMessages.  However, for some reason at the login screens, this does not seem to work. I can send mouseclick messages, but none of my keystrokes are acknowledged.  Is the game using directinput or something?  Is there a mechanism for me to stick things into the keyboard buffer (w/o writing a device driver)?  

My program runs the game as a child process.  Do I have to dig in, find the relevant directx functions and hook them?  (Was hoping it'd be easier than that).

Thanks in advance.
Question by:mrcurious
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LVL 86

Accepted Solution

jkr earned 150 total points
ID: 2588790
I assume you're sending the messages to the window that created the login dialog, not the dialog itself - this would result in the behaviour you described...

BTW: You emulate mouse events by using the 'mouse_event()' API, it's designed for this purpose - here's the description from the VC++ docs:

The mouse_event function synthesizes mouse motion and button clicks.

Windows NT only: This function has been superseded. Use MouseEventEx instead.

VOID mouse_event( DWORD dwFlags,
 // flags specifying various motion/click variants
 // horizontal mouse position or position change
 // vertical mouse position or position change
DWORD dwData,
 // amount of wheel movement
DWORD dwExtraInfo
 // 32 bits of application-defined information


A set of flag bits that specify various aspects of mouse motion and button clicking. The bits in this parameter can be any reasonable combination of the following values: Value
 Specifies that the dx and dy parameters contain normalized absolute coordinates. If not set, those parameters contain relative data: the change in position since the last reported position. This flag can be set, or not set, regardless of what kind of mouse or mouse-like device, if any, is connected to the system. For further information about relative mouse motion, see the following Remarks section.
 Specifies that movement occurred.
 Specifies that the left button changed to down.
 Specifies that the left button changed to up.
 Specifies that the right button changed to down.
 Specifies that the right button changed to up.
 Specifies that the middle button changed to down.
 Specifies that the middle button changed to up.
 Windows NT only: Specifies that the wheel has been moved, if the mouse has a wheel. The amount of movement is given in dwData

The flag bits that specify mouse button status are set to indicate changes in status, not ongoing conditions. For example, if the left mouse button is pressed and held down, MOUSEEVENTF_LEFTDOWN is set when the left button is first pressed, but not for subsequent motions. Similarly, MOUSEEVENTF_LEFTUP is set only when the button is first released.


Specifies the mouse’s absolute position along the x-axis or its amount of motion since the last mouse event was generated, depending on the setting of MOUSEEVENTF_ABSOLUTE. Absolute data is given as the mouse’s actual x-coordinate; relative data is given as the number of mickeys moved. A mickey is the amount that a mouse has to move for it to report that it has moved.


Specifies the mouse’s absolute position along the y-axis or its amount of motion since the last mouse event was generated, depending on the setting of MOUSEEVENTF_ABSOLUTE. Absolute data is given as the mouse’s actual y-coordinate; relative data is given as the number of mickeys moved.


If dwFlags is MOUSEEVENTF_WHEEL, then dwData specifies the amount of wheel movement. A positive value indicates that the wheel was rotated forward, away from the user; a negative value indicates that the wheel was rotated backward, toward the user. One wheel click is defined as WHEEL_DELTA, which is 120.

If dwFlags is not MOUSEEVENTF_WHEEL, then dwData should be zero.


Specifies an additional 32-bit value associated with the mouse event. An application calls GetMessageExtraInfo to obtain this extra information.

Expert Comment

ID: 2588850
You say you "simulate keystrokes" but not how. Are you sending WM-CHAR and/or WM_KEYUP and/or WM_KEYDOWN messages, or something else?
LVL 86

Expert Comment

ID: 2589041
Ooops, I meant 'keybd_event()', of course...

Author Comment

ID: 2590137

Turns out it was my bad.  I used SendMessage instead of PostMessage!  But your information was useful for future reference.  I had no clue about those functions.


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