This function returns the dialog box base units used by Windows to create dialog boxes. Both Windows and applications use these units to convert the width and height of dialog boxes and controls from dialog units, as specified in dialog box templates, to pixels, and vice versa.
A 32-bit value that contains the dialog base units indicates success. The low-order word of the return value contains the horizontal dialog box base unit, and the high-order word contains the vertical dialog box base unit.
Windows Embedded CE does not support any extended error values for this function.
The results returned by GetDialogBaseUnits are always derived from the system font. For both fixed pitch and variable pitch fonts, the horizontal base unit returned by GetDialogBaseUnits is equal to the average width, in pixels, of all of the uppercase and lowercase Roman characters; the vertical base unit is equal to the height, in pixels, of the font.
You can use the GetTextMetrics and GetTextExtentPoint32 functions to calculate these values for a selected font. However, by using the MapDialogRect function, you can avoid errors that might result if your calculations differ from those performed by the system.
Each horizontal base unit is equal to 4 horizontal dialog template units; each vertical base unit is equal to 8 vertical dialog template units. Therefore, to convert dialog template units to pixels, use the following formulas.
pixelX = (templateunitX * baseunitX) / 4 pixelY = (templateunitY * baseunitY) / 8
Similarly, to convert from pixels to dialog template units, use the following formulas.
templateunitX = (pixelX * 4) / baseunitX templateunitY = (pixelY * 8) / baseunitY
The multiplication is performed before the division to avoid rounding problems if base units are not divisible by 4 or 8.