|OnScreen: for Windows; On-Screen Keyboards with Assistive Technology; Version 1.78 Release 4; User's Guide|
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OnScreen is a standard Windows Application and does not require any special drivers, and should work with all keyboard and mouse emulation drivers that are compatible with the ones that ship with Microsoft Windows.
For other pointing devices, OnScreen calls and uses the GetAsyncKeyState & GetKeyState API calls for certain actions of the mouse. These must be supported by the hardware & driver emulating the mouse. The 1.40 release addresses some of these limitations, and OnScreen operates properly with Joystick-To-Mouse, CrossScanner, Mouse Keys, and other pointing methods that do not use the actual mouse driver.
When working with Virtual Machines, certain pointing device functions operate differently because of the way the mouse integrates through the virtual machine layer. Some functions may not operate correctly, or the virtual machine may need to be full screen (or windowed) to operate correctly. We are aware of issues with the Windows API ClipCursor and SetMousePos when using VMWare and Parallels virtual machines. These limitations then affects the keyboard scanning feature when running OnScreen in Windows within a virtual machine.