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Chapter 4 - Font Manager / Font Manager Reference

Routines / Getting the Characteristics of a Font

FontMetrics

The FontMetrics procedure gets fractional measurements for the font, size, and style specified in the current graphics port.

PROCEDURE FontMetrics (VAR theMetrics: FMetricRec);

theMetrics

A font metrics record that contains the font measurement information, in fractional values.

DESCRIPTION

The FontMetrics procedure returns measurements for the ascent, descent, leading, and width of the largest glyph in the font for the font, size, and style specified in the current graphics port. FontMetrics returns this information in a font metrics record.

The font metrics record (of data type FMetricRec) contains a handle to the global width table, which in turn contains a handle to the associated font family resource for the current font (the font in the current graphics port). It also contains the values of four measurements for the current font.

Type FMetricRec =
RECORD
   ascent: Fixed;    {baseline to top}
   descent: Fixed;   {baseline to bottom}
   leading: Fixed;   {leading between lines}
   widMax: Fixed;    {maximum glyph width}
   wTabHandle: Handle; {handle to global width table}
END;

Field Description

ascent

The measurement from the baseline to the ascent line of the font.

descent

The measurement from the baseline to the descent line of the font.

leading

The measurement from the descent line to the ascent line below it.

widMax

The width of the largest glyph in the font.

wTabHandle

A handle to the global width table.

You can determine the line height, in pixels, by adding the values of the ascent, descent, and leading fields of the font metrics record.

The FontMetrics procedure is similar to QuickDraw's GetFontInfo procedure, except that FontMetrics returns fractional values for greater accuracy in high-resolution printing. FontMetrics also does not take into account any additional widths that are added by QuickDraw when it applies styles to the glyphs in a font.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro for the FontMetrics procedure is

Trap macro
_FontMetrics

SEE ALSO

The GetFontInfo procedure is described in the chapter "QuickDraw Text" in this book.