Microsoft KB Archive/133065

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Determining Connected Joysticks Under Windows

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Q133065

4.00 WINDOWS kbmm

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The information in this article applies to:


 * Microsoft Platform Software Development Kit (SDK), on platform(s):
 * Microsoft Windows 98
 * Microsoft Windows 95
 * the operating system: Microsoft Windows 2000

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SUMMARY
The joystick API joyGetNumDevs behaves differently on Windows 95 than it does in other implementations, so a different technique, involving joyGetPosEx, is required to determine the number of joysticks available during game play.

This article provides the code for a function called JoysticksConnected that demonstrates how to determine the number of connected joysticks.

MORE INFORMATION
Under Windows 95, the joyGetNumDevs API returns: 0 if no joystick drivers have been installed or 16 (the highest possible number of connected joysticks) in all other cases. This behavior is by design. To determine the actual number of joysticks installed, use the joyGetPosEx API.

The design for Windows 95 joystick drivers calls for the driver to support two independent joystick input devices. Therefore, during driver installation, two registry keys are created, and initialized. The keys correspond to joystick 0 and joystick 1, respectively.

If no joystick support is available (no drivers), joyGetNumDevs returns 0.

When joyGetNumDevs returns a non-zero value, joyGetPosEx returns JOYERR_NOERRROR or JOYERR_PARMS (defined in the file MMSYSTEM.H). You can examine the return values and determine the number of joysticks connected as shown below. NOTE: when linking, WINMM.LIB must be from the Win32 SDK:

  int JoysticksConnected {  // determine number of joysticks installed in Windows 95

JOYINFOEX info;     // extended information

int njoyId = 0;     // first joystick

int nConnected = 0; // goal - number of joysticks connected

MMRESULT dwResult;  // examine return values

// Loop through all possible joystick IDs until we get the error // JOYERR_PARMS. Count the number of times we get JOYERR_NOERROR // indicating an installed joystick driver with a joystick currently // attached to the port.

while ((dwResult = joyGetPosEx(njoyId++,&info)) != JOYERR_PARMS)

if (dwResult == JOYERR_NOERROR) ++nConnected;   // the count of connected joysticks

return nConnected; // return the count of joysticks found

} // JoysticksConnected Additional query words: 4.00 JOYERR connect kbinf

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Technology : kbWin32SDKSearch kbAudDeveloper kbSDKSearch