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class

font% : class?

  superclass: object%

A font is an object which determines the appearance of text, primarily when drawing text to a device context. A font is determined by seven properties:

  • size — The size of the text, either in points (the default) or logical drawing units, depending on the “size-in-pixels?” property (see below).

  • family — A platform- and device-independent font designation. The families are:

    • 'default

    • 'decorative

    • 'roman

    • 'script

    • 'swiss

    • 'modern (fixed width)

    • 'symbol (Greek letters and more)

    • 'system (similar to the font to draw control labels, but see normal-control-font)

    The terminology “family” and “face” is mangled relative to its usual meaning. A font% “face” is really used more like a font family in the usual terminology or more generally as a face-description string that is combined with other font% attributes to arrive at a face. A font% “family” is a kind of abstract font family that is mapped to a particular font family on a given platform.

  • face — A string face name, such as "Courier". The format and meaning of a face name is platform- and device-specific. If a font’s face name is #f, then the font’s appearance depends only on the family. If a face is provided but no mapping is available for the face name (for a specific platform or device), then the face name is ignored and the family is used. See font-name-directory<%> for information about how face names are mapped for drawing text.

  • style — The slant style of the font, one of:
    • 'normal

    • 'slant (a.k.a “oblique”)

    • 'italic

  • weight — The weight of the font, one of:
    • 'normal

    • 'light

    • 'bold

  • underline? — #t for underlined, #f for plain.

  • smoothing — Amount of anti-alias smoothing, one of:
    • 'default (platform-specific, sometimes user-configurable)

    • 'partly-smoothed (gray anti-aliasing)

    • 'smoothed (sub-pixel anti-aliasing)

    • 'unsmoothed

  • size-in-pixels? — #t if the size of the font is in logical drawing units (i.e., pixels for an unscaled screen or bitmap drawing context), #f if the size of the font is in points (which can depend on screen resolution).

  • hinting — Whether font metrics should be rounded to integers:
    • 'aligned (the default) — rounds to integers to improve the consistency of letter spacing for pixel-based targets, but at the expense of making metrics unscalable

    • 'unaligned disables rounding

To avoid creating multiple fonts with the same characteristics, use the global font-list% object the-font-list.

See also font-name-directory<%>.

constructor

(make-object font%)  (is-a?/c font%)

(make-object font% size    
  family    
  [style    
  weight    
  underline?    
  smoothing    
  size-in-pixels?    
  hinting])  (is-a?/c font%)
  size : (integer-in 1 1024)
  family : font-family/c
  style : font-style/c = 'normal
  weight : font-weight/c = 'normal
  underline? : any/c = #f
  smoothing : font-smoothing/c = 'default
  size-in-pixels? : any/c = #f
  hinting : font-hinting/c = 'aligned
(make-object font% size    
  face    
  family    
  [style    
  weight    
  underline?    
  smoothing    
  size-in-pixels?    
  hinting])  (is-a?/c font%)
  size : (integer-in 1 1024)
  face : string?
  family : font-family/c
  style : font-style/c = 'normal
  weight : font-weight/c = 'normal
  underline? : any/c = #f
  smoothing : font-smoothing/c = 'default
  size-in-pixels? : any/c = #f
  hinting : font-hinting/c = 'aligned
When no arguments are provided, creates an instance of the default font. If no face name is provided, the font is created without a face name.

See font% for information about family, style, weight, smoothing, size-in-pixels?, and hinting. font-name-directory<%>.

See also make-font.

method

(send a-font get-face)  (or/c string? #f)

Gets the font’s face name, or #f if none is specified.

method

(send a-font get-family)  font-family/c

Gets the font’s family. See font% for information about families.

method

(send a-font get-font-id)  exact-integer?

Gets the font’s ID, for use with a font-name-directory<%>. The ID is determined by the font’s face and family specifications, only.

method

(send a-font get-hinting)  font-hinting/c

Gets the font’s hinting. See font% for information about hinting.

method

(send a-font get-point-size)  (integer-in 1 1024)

Gets the font’s size (roughly the height). Despite the method name, the size may be in logical units instead of points, depending on the result of get-size-in-pixels.

Due to space included in a font by a font designer, a font tends to generate text that is slightly taller than the nominal size.

method

(send a-font get-size-in-pixels)  boolean?

Returns #t if the size reported by get-point-size is in logical drawing units, #f if it is in points.

For a size in points and a screen or bitmap drawing context, the logical height depends on the resolution of the screen.

method

(send a-font get-smoothing)  font-smoothing/c

Gets the font’s anti-alias smoothing mode. See font% for information about smoothing.

method

(send a-font get-style)  font-style/c

Gets the font’s slant style. See font% for information about styles.

method

(send a-font get-underlined)  boolean?

Returns #t if the font is underlined or #f otherwise.

method

(send a-font get-weight)  font-weight/c

Gets the font’s weight. See font% for information about weights.

method

(send a-font screen-glyph-exists? c    
  [for-label?])  boolean?
  c : char
  for-label? : any/c = #f
Returns #t if the given character has a corresponding glyph when drawing to the screen or a bitmap, #f otherwise.

If the second argument is true, the result indicates whether the glyph is available for control labels. Otherwise, it indicates whether the glyph is available for dc<%> drawing.

For dc<%> drawing, due to automatic font substitution when drawing or measuring text, the result of this method does not depend on this font’s attributes (size, face, etc.). The font’s attributes merely provide a hint for the glyph search.

See also glyph-exists? .