_twM33()
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     This is similar to _twM0A() except that it does not affect the
     hardware. It hides the cursor, sets it to the center of the
     screen, sets the default cursor shape and the default mickey to
     pixel ratio.

       Arguments:

     None.

       Return:

     -1 if the mouse driver is installed.
      0 otherwise.

       Example:

     _twM33()