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Handling Joystick Input in Visual Basic
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This tutorial will use the Windows API to
get joystick input.
API
Definitions
Here is a list of what functions and type's
we will need. I suggest adding a module or
class to your project and adding these there.
Function's
Public
Declare Function joyGetPosEx Lib "winmm.dll" (ByVal
uJoyID As Long, _
pji As JOYINFOEX) As Long
Public
Declare Function joyGetDevCapsA Lib "winmm.dll" (ByVal
uJoyID As Long, _
pjc As JOYCAPS, ByVal cjc As Long) As Long
joyGetPosEx returns input information.
joyGetDevCapsA returns information on the
joystick.
Type's
Public Type JOYCAPS
wMid As Integer
wPid As Integer
szPname As String * 32
wXmin As Long
wXmax As Long
wYmin As Long
wYmax As Long
wZmin As Long
wZmax As Long
wNumButtons As Long
wPeriodMin As Long
wPeriodMax As Long
wRmin As Long
wRmax As Long
wUmin As Long
wUmax As Long
wVmin As Long
wVmax As Long
wCaps As Long
wMaxAxes As Long
wNumAxes As Long
wMaxButtons As Long
szRegKey As String * 32
szOEMVxD As String * 260
End Type
Public Type JOYINFOEX
dwSize As Long
dwFlags As Long
dwXpos As Long
dwYpos As Long
dwZpos As Long
dwRpos As Long
dwUpos As Long
dwVpos As Long
dwButtons As Long
dwButtonNumber As Long
dwPOV As Long
dwReserved1 As Long
dwReserved2 As Long
End Type
Other
public variables
Public
JoyNum As Long
Public MYJOYEX As JOYINFOEX
Public MYJOYCAPS As JOYCAPS
Public CenterX As Long
Public CenterY As Long
Public JoyButtons(15) as Boolean
Public CurrentJoyX As Long
Public CurrentJoyY As Long
Coding the Input
Create a function named StartJoystick.
All this does is get the CAPS
and Center positions:
Public Function StartJoystick(Optional ByVal
JoystickNumber As Long = 0) As Boolean
JoyNum = JoystickNumber
If
joyGetDevCapsA(JoyNum, MYJOYCAPS, 404) <> 0
Then 'Get joystick info
StartJoystick = False
Else
Call joyGetPosEx(JoyNum, MYJOYEX)
CenterX = MYJOYEX.dwXpos
CenterY = MYJOYEX.dwYpos
StartJoystick = True
End If
End Function
As you can see, it's not too complicated.
The JoystickNumber variable is what
joystick you want to get input from. This is usually zero, but can be one
[or two for hardcore users...:)].
Next, add a function called PollJoystick.
This function will get all the information
from the joystick, then sort it out:
Public Sub PollJoystick()
Dim i As Long
Dim t As Long
MYJOYEX.dwSize = 64
MYJOYEX.dwFlags = 255
' Get the joystick information
Call joyGetPosEx(JoyNum, MYJOYEX)
t = myJoy.dwButtons
For i = 15 To 0 Step -1
JoyButtons(i) = False
If
(2 ^ i) <= t Then
t = t - (2 ^ i)
JoyButtons(i) = True
End If
Next i
CurrentJoyX = MYJOYEX.dwXpos
CurrentJoyY = MYJOYEX.dwYpos
End Sub
Now you have the ability to get input
from the joystick. But how do you
use it? And
what's with the complicated code? Well,
that complicated code is what tells
you what buttons
are pressed. How? When you press button
zero on your joystick, the joystick
tells the
computer 1. Press one, it says 2. But press
two, it says four. Press three, and its
8. See the pattern? If not, here
it is:
2^0=1
2^1=2
2^2=4
2^3=8
2^4=16
2^5=32
See? So press buttons zero, two and three,
and the joystick tells the computer 11.
How do we sort this out? Start with
the highest
number, then goto zero. If the current
number is within the input number
(11 in our example),
then subtract that from from the number.
So in our example, it would get the 2^3=8,
so subtract it, leaving us with 3. Then
it gets to 2^1=2, subtract it, leaving
1. So
then 2^0=1, subtract it, leaving zero.
Get it? If not, trust me (I'm bad
at explaining
algorithms).
Done
Download the source
code to see it in action,
in a stupid little game.
About
this Tutorial
This tutorial is from The
Game Progamming Wiki which is published under the
GNU Free Documentation License 1.2.
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