{\rtf1\ansi\ansicpg1252\deff0\deflang1033{\fonttbl{\f0\fswiss\fcharset0 Arial;}} \viewkind4\uc1\pard\b\f0\fs20 1. Ascender\b0\par \par \b FT_Face\b0 - The face's ascender is the vertical distance from the baseline to the topmost point of \b any\b0 glyph in the face. This field's value is positive, expressed in \b font units\b0 . Some font designs use a value different from `bbox.yMax'. Only relevant for scalable formats.\par \par \b FT_Size_Metrics\b0 - Scaled versions of 'face->ascender'. Expressed in \b 26.6\b0 fixed point pixels. Positive for ascenders above the baseline.\par \par \b hhea\b0 - Distance from baseline of highest ascender.\par \par \b sTypoAscender\b0 - The typographic ascender for this font. Remember that this is not the same as the Ascender value in the 'hhea' table, which Apple defines in a far different manner. One good source for sTypoAscender in \b Latin based\b0 fonts is the Ascender value from an AFM file.\par \par \b usWinAscent\b0 - The ascender metric for Windows. This, too, is distinct from Apple's Ascender value and from the sTypoAscender values. usWinAscent is computed as the \b yMax for all characters in the Windows ANSI character set\b0 . usWinAscent is used to compute the Windows font height and default line spacing. For platform 3 encoding 0 fonts, it is the same as yMax. Windows will clip the bitmap of any portion of a glyph that appears above this value. Some applications use this value to determine default line spacing. This is strongly discouraged. The typographic ascender, descender and line gap fields in conjunction with unitsPerEm should be used for this purpose. Developers should set this field keeping the above factors in mind. \par If any clipping is unacceptable, then the value should be set to yMax. However, if a developer desires to provide appropriate default line spacing using this field, for those applications that continue to use this field for doing so (against OpenType recommendations), then the value should be set appropriately. In such a case, it may result in some glyph bitmaps being clipped.\par \par \par \b 2. Descender\b0\par \par \b FT_Face\b0 - The face's descender is the vertical distance from the baseline to the bottommost point of \b any\b0 glyph in the face. This field's value is negative for values below the baseline. It is expressed in \b font units\b0 . Some font designs use a value different from `bbox.yMin'. Only relevant for scalable formats.\par \par \b FT_Size_Metrics\b0 - Scaled versions of 'face->descender'. Expressed in \b 26.6\b0 fixed point pixels. Negative for descenders below the baseline.\par \par \b hhea\b0 - Distance from baseline of lowest descender.\par \par \b sTypoDescender\b0 - The typographic descender for this font. Remember that this is not the same as the Descender value in the 'hhea' table, which Apple defines in a far different manner. One good source for sTypoDescender in \b Latin based\b0 fonts is the Descender value from an AFM file.\par \par \b usWinDescent\b0 - The descender metric for Windows. This, too, is distinct from Apple's Descender value and from the sTypoDescender values. usWinDescent is computed as the \b -yMin for all characters in the Windows ANSI character set\b0 . usWinDescent is used to compute the Windows font height and default line spacing. For platform 3 encoding 0 fonts, it is the same as -yMin. Windows will clip the bitmap of any portion of a glyph that appears below this value. Some applications use this value to determine default line spacing. This is strongly discouraged. The typographic ascender, descender and line gap fields in conjunction with unitsPerEm should be used for this purpose. Developers should set this field keeping the above factors in mind. \par If any clipping is unacceptable, then the value should be set to yMin. However, if a developer desires to provide appropriate default line spacing using this field, for those applications that continue to use this field for doing so (against OpenType recommendations), then the value should be set appropriately. In such a case, it may result in some glyph bitmaps being clipped.\par \par \par \b 3. Height\b0\par \par \b FT_Face\b0 - The face's height is the vertical distance from \b one baseline to the next\b0 when writing several lines of text. Its value is always positive, expressed in \b font units\b0 . The value can be computed as 'ascender+descender+\b line_gap\b0 ' where the value of `line_gap' is also called 'external leading'. Only relevant for scalable formats.\par \par \b FT_Size_Metrics\b0 - Scaled versions of 'face->height'. Expressed in \b 26.6\b0 fixed point pixels. Always positive.\par \par \par \b 4. Line Gap\b0\par \par \b sTypoLineGap\b0 - The typographic line gap for this font. Remember that this is not the same as the LineGap value in the 'hhea' table, which Apple defines in a far different manner.\par \par \b hhea\b0 - typographic line gap.\par \par \par \b 5. Notes not to be forgotten\b0\par \par \b FT_Size_Metrics\b0 - Unfortunately, due to glyph hinting, these values might not be exact for certain fonts. Thus they must be treated as unreliable with an error margin of at least one pixel! Indeed, the only way to get the exact pixel ascender and descender is to render _\b all\b0 _ glyphs. As this would be a definite performance hit, it is up to client applications to perform such computations.\par \par \b hhea\b0 - The values for ascent, descent and lineGap represent the design intentions of the font's creator rather than any computed value.\par \par }