The dimensions that an application passes to GpiSetCharBox and that GpiQueryCharBox returns are fixed-point values. A fixed value is a 32-bit value whose high-order 16 bits contain the integral part of the floating-point number and whose low-order 16 bits contain the fractional part. The fractional part is the numerator of a fraction whose denominator is fixed at 65536. The MAKEFIXED macro provides a method for producing fixed values. If, for example, one of the character cell dimensions were 7.635 world units, an application could obtain the corresponding fixed value by using the MAKEFIXED macro, passing 7 as the first argument and 41615 as the second.

The purpose of the character cell is to assist other font metrics to define text lines. For example, if you planned to have an average text line of 60 characters, dividing your output width by 60 would provide your character cell width.

DevQueryCaps can be used to provide information about suitable character cell values. DevQueryCaps returns two sets of values that can influence the character cell:

• Default cell values
  
  
  • CAPS_GRAPHICS_CHAR_WIDTH
    
  • CAPS_GRAPHICS_CHAR_HEIGHT.
  
  Device resolution
  -
  CAPS_HORIZONTAL_FONT_RES
  -
  CAPS_VERTICAL_FONT_RES.

  The default cell values return the size of the default character cell in pels. Convert the device resolution into character cell values by multiplying it by the desired point size, then dividing by 72 (72.2818).

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