[This is preliminary documentation and subject to change.]
Best Practice (Designed for Microsoft® Windows® Logo)
Your application should make use of the following system settings to be compatible with multi-monitor support.
SM_XVIRTUALSCREEN, SM_YVIRTUALSCREEN
SM_CXVIRTUALSCREEN, SM_CYVIRTUALSCREEN
SM_SAMEDISPLAYFORMAT
SM_CMONITORS
These settings are queried using the GetSystemMetrics function.