BUG: SystemParametersInfo() Does Not Modify WIN.INI

• Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

SYMPTOMS

When a program uses the SystemParametersInfo() function with the SPI_SETMOUSEBUTTONSWAP and SPIF_UPDATEINIFILE flags to reverse the mouse buttons' orientation and modify WIN.INI, the appropiate changes to WIN.INI are not made. The next time Windows starts, the buttons are back to the default orientation.

CAUSE

Calling SystemParametersInfo (SPI_SETMOUSEBUTTONSWAP, TRUE, NULL, SPIF_UPDATEINIFILE), modifies or creates the SwapMouseButtons entry in the "Windows" section of WIN.INI. However, the value this function writes is "1", unlike the Control Panel's mouse applet which writes "Yes".

"Yes", not "1", is the value recognized to swap the buttons during the startup of Windows. When Windows loads the settings from WIN.INI, Windows looks for the "SwapMouseButtons" entry in the "Windows" section, expecting a value of "Yes". If another value is encountered, Windows defaults to "No", which will cause Windows to use the default orientation of the mouse buttons.

RESOLUTION

An alternative way to swap the mouse buttons and modify the entry correctly is to use both SwapMouseButton() and WriteProfileString() to alter the mouse button orientation and explicitly modify the initialization file. The following code shows the method explained:

  :
  :
  SwapMouseButton (TRUE);
  WriteProfileString ("Windows", "SwapMouseButtons", "Yes");
  :
  :

STATUS

Microsoft has confirmed this to be a bug in the Microsoft Windows SDK version 3.1. We will post new information here in the Microsoft Knowledge Base when it becomes available.