Simulating Keyboard with SendInput API in DirectInput applications

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I’ve found the solution to my own problem. So, I thought I’d post here to help anyone who may have similar issues in the future.

The keyup command was not working properly because when only sending the scan code, the keyup must be OR’ed with the scan code flag (effectively enabling both flags) to tell the SendInput() API that this is a both a KEYUP and a SCANCODE command.

For instance, the following code will properly issue a scan code key-up:

INPUT[] InputData = new INPUT[1];

InputData[0].Type = (UInt32)InputType.KEYBOARD;
//InputData[0].Vk = (ushort)DirectInputKeyScanCode;  //Virtual key is ignored when sending scan code
InputData[0].Scan = (ushort)DirectInputKeyScanCode;
InputData[0].Flags = (uint)KeyboardFlag.KEYUP | (uint)KeyboardFlag.SCANCODE;
InputData[0].Time = 0;
InputData[0].ExtraInfo = IntPtr.Zero;

// Send Keyup flag "OR"ed with Scancode flag for keyup to work properly
SendInput(1, InputData, Marshal.SizeOf(typeof(INPUT)))

Thanks to Hans for the response. I did some investigating and sending two messages back to back like the original example does indeed simulate a “keypress” but it’s very fast. It would not work well for a movement command, but would be ideal when action keys are to be “tapped” and not held down.

Also, the virtual key field is ignored when sending a scan code. MSDN had the following to say on the subject:

“Set the KEYEVENTF_SCANCODE flag to define keyboard input in terms of the scan code. This is useful to simulate a physical keystroke regardless of which keyboard is currently being used. The virtual key value of a key may alter depending on the current keyboard layout or what other keys were pressed, but the scan code will always be the same.”

http://msdn.microsoft.com/en-us/library/ms646271%28v=VS.85%29.aspx

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