This function consolidates the current functions of WinDBCSIMEControl and WinDBCSModeControl functions.

IM_CTL_MOD_ROMANENABLE/DISABLE and IM_CTL_MOD_ROMAN/NOROMAN are only valid for Japanese CodePages.

ulKbdMask is valid at setting time (IM_CTL_REQ_SET) and specifies bits of ulKbdMode to be affected. hwndIM is filled on return at IM_CTL_REQ_QUERY.

hwndInherit must be set when issuing a set request (ulReqType=IM_CTL_REQ_SET) with IM_CTL_MOD_INHERIT_ON. For a query request, if a specified frame is in inherit mode, hwndInherit is filled with the Inherit Frame handle.

As the result of IM_CTL_REQ_SET, the Input Method Support module GTR (General Transaction Router) may generate WM_CHAR messages and send them to the specified Frame window. The WM_CHAR messages will contain VKeys representing a new KbdMode.

When IM_CTL_MOD_DBCSINBYTE is set, PM sends two WM_CHARs which contain the first and second bytes of a DBCS ASCII character. Otherwise, PM only sends one WM_CHAR message.

IM_CTL_MOD_INTERIMON is usually OFF. IM_CTL_MOD_FINALONLY is the default for all applications except those using the Korean CodePage. With IM_CTL_MOD_FINALONLY, PM and IM only generate finalized character messages.

The mode INTERIMON is used mostly by Hangeulized applications. When INTERIMON set ON, an IM attached to the frame generates both interim and finalized Hangeul characters, if it has such a capability. PM then returns them to the applications with WM_CHAR messages.

In case of an interim character, the Scancode field of the message contains 0xF0. If it's 0xF1, it represents a finalized Hangeul character.

Note: Under INTERIMON mode, IM will not usually display the interim Hangeul characters. Applications have a chance to hide the conversion window explicitly through an IM_SHOWWINDOW message.