Code to determine the current DPI setting. Displays the percentage I should bump up my visual controls by in order to match the users settings.

fontfactor.prg

LOCAL liHDC, liPixelsPerInchX, ;
      liPixelsPerInchY, lnFontFactor

DECLARE INTEGER GetDC IN Win32API ;
   INTEGER iHDC

DECLARE INTEGER GetDeviceCaps IN WIN32API ;
   INTEGER iHDC, INTEGER iIndex

#DEFINE cnLOG_PIXELS_X 88
#DEFINE cnLOG_PIXELS_Y 90

liHDC = GetDC(ThisForm.HWnd)
liPixelsPerInchX = GetDeviceCaps(liHDC, cnLOG_PIXELS_X)
liPixelsPerInchY = GetDeviceCaps(liHDC, cnLOG_PIXELS_Y)

IF liPixelsPerInchX <= 96
   ** The user has selected "normal" font size
   lnFontFactor = 1
ELSE
   ** The user wants to use large fonts. The
   ** calculation will determine how large
   ** (by percentage) the fonts should be.
   lnFontFactor = 1 + ((liPixelsPerInchX - 96)/96)
ENDIF

MESSAGEBOX("The DPI 'font factor' is: " + ; 
           ALLTRIM(TRANSFORM(lnFontFactor)),0,"Font Factor")