Need to convert mouse coordinates into PS position or row an

Question

I'm using Whllapi to connect and automate mainframe emulator. I need to find a underlying field when user move mouse or click on a field at emulator screen. To identify a field on mainframe emulator i need to know row and column or PS position. I need to convert mouse position (in pixels) to emulator row and column. But there is no API in whllapi that provides such functionality.

 

I used whllapi api "QueryWindowCoordinates" and 'WindowStatus" to get emulator window coordinates and window hwnd. I used that handle in window API "SreenToCleint" to get mouse position with respect to emulator window. But i'm unable to translate those co-ordinates into emulator rows and column. I tried many algorithm but unable to get consistent results. I need translate mouse position precisely into PS position. Whllap documentation has mentioned "WindowStatus" api to return font sizes for x and y but i'm unable to retrieve any value from Rumba emulator. In order to get fond height and width, I also tried window api 'GetTextMetrcies' but that was not much help either.