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Direct Input
Direct Input is a component of DirectX that gives you direct access to the current state of
the keyboard (among other devices). This is obviously quite useful for game programming purposes
and so I will outline its use here.
Dim dx As New DirectX7
Dim di As DirectInput
Dim diDEV As DirectInputDevice
Set di = dx.DirectInputCreate()
Set diDEV = di.CreateDevice("GUID_SysKeyboard")
diDEV.SetCommonDataFormat DIFORMAT_KEYBOARD
diDEV.SetCooperativeLevel Me.hWnd, DISCL_BACKGROUND Or DISCL_NONEXCLUSIVE
diDEV.Acquire
As with DirectDraw, we have to create an instance of the DirectX7 object and use it to define
a DirectInput object, "di". We then need to set the direct input device to the one in which we
are interested, in this case the keyboard. So, we call the "di.CreateDevice" method and request
it returns the system keyboard object.
Next we have to set the data format of the device to the keyboard data format. We do this with
the "diDEV.SetCommonDataFormat". We could also use this to set the data format to Joy1, Joy2,
or the mouse.
Just like DirectDraw, we must set the cooperative level. We pass the handle to the window for
which we would like to receive keyboard input, if this is the form in which the code resides we
can pass "Me.hWnd". "DISCL_BACKGROUND" and "DISCL_NONEXCLUSIVE" allows other programs access to
keystrokes, and give us access to all keystrokes.
Now that we've set up the device which we'd like to use, we have to acquire it using the
"diDEV.Acquire" method.
Dim diState As DIKEYBOARDSTATE
Dim i As Integer
Public aKeys(211) As Boolean
diDEV.GetDeviceStateKeyboard diState
For i = 1 To 211
If diState.Key(i) <> 0 Then
aKeys(i) = True
Else
aKeys(i) = False
End If
Next
Everything is setup, now we can reap what we have sown (no, I'm not suggesting you go plant your
keyboard in your garden in order to cultivate input). "diState" is an object that will contain the states of all
the keys on the keyboard, and we can tap into this using an array and a loop. Each key on the keyboard corresponds
to an integer value between 0 and 211. If we then make an array with 212 members we can keep track of which
keys are active and when. Use the "diDEV.GetDeviceStateKeyboard" method to fill the "diState" variable, and
then extract the data from this into our array "aKeys" using a "for" loop.
Have a look at my DirectX 7 sample project to see which keypress corresponds to
which value and to see DirectInput in action.
