#lang scribble/doc @(require "common.ss") @defclass/title[font% object% ()]{ A @defterm{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: @itemize[ @item{size --- The size of the text, either in points (the default) or logical drawing units, depending on the ``size-in-pixels?'' property (see below).} @item{family --- A platform- and device-independent font designation. The families are: @itemize[ @item{@indexed-scheme['default]} @item{@indexed-scheme['decorative]} @item{@indexed-scheme['roman]} @item{@indexed-scheme['script]} @item{@indexed-scheme['swiss]} @item{@indexed-scheme['modern] (fixed width)} @item{@indexed-scheme['symbol] (Greek letters and more)} @item{@indexed-scheme['system] (similar to the font to draw control labels, but see @racket[normal-control-font])} ] @margin-note{The terminology ``family'' and ``face'' is mangled relative to its usual meaning. A @racket[font%] ``face'' is really a font family in the usual terminology, while a @racket[font%] ``family'' is a kind of abstract font family that is mapped to a particular font family on a given platform.}} @item{face --- A string face name, such as @scheme["Courier"]. The format and meaning of a face name is platform- and device-specific. If a font's face name is @scheme[#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 @scheme[font-name-directory<%>] for information about how face names are mapped for drawing text.} @item{style --- The slant style of the font, one of: @itemize[ @item{@indexed-scheme['normal]} @item{@indexed-scheme['slant] (a.k.a ``oblique'')} @item{@indexed-scheme['italic]} ]} @item{weight --- The weight of the font, one of: @itemize[ @item{@indexed-scheme['normal]} @item{@indexed-scheme['light]} @item{@indexed-scheme['bold]} ]} @item{underline? --- @scheme[#t] for underlined, @scheme[#f] for plain.} @item{smoothing --- Amount of anti-alias smoothing, one of: @itemize[ @item{@indexed-scheme['default] (platform-specific, sometimes user-configurable)} @item{@indexed-scheme['partly-smoothed] (gray anti-aliasing)} @item{@indexed-scheme['smoothed] (sub-pixel anti-aliasing)} @item{@indexed-scheme['unsmoothed]} ]} @item{size-in-pixels? --- @scheme[#t] if the size of the font is in logical drawing units (i.e., pixels for an unscaled screen or bitmap drawing context), @scheme[#f] if the size of the font is in points (which can depend on screen resolution).} ] To avoid creating multiple fonts with the same characteristics, use the global @scheme[font-list%] object @indexed-scheme[the-font-list]. See also @scheme[font-name-directory<%>]. @defconstructor*/make[(() ([size (integer-in 1 255)] [family (one-of/c 'default 'decorative 'roman 'script 'swiss 'modern 'symbol 'system)] [style (one-of/c 'normal 'italic 'slant) 'normal] [weight (one-of/c 'normal 'bold 'light) 'normal] [underline? any/c #f] [smoothing (one-of/c 'default 'partly-smoothed 'smoothed 'unsmoothed) 'default] [size-in-pixels? any/c #f]) ([size (integer-in 1 255)] [face string?] [family (one-of/c 'default 'decorative 'roman 'script 'swiss 'modern 'symbol 'system)] [style (one-of/c 'normal 'italic 'slant) 'normal] [weight (one-of/c 'normal 'bold 'light) 'normal] [underline? any/c #f] [smoothing (one-of/c 'default 'partly-smoothed 'smoothed 'unsmoothed) 'default] [size-in-pixels? any/c #f]))]{ 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 @scheme[font%] for information about @scheme[family], @scheme[style], and @scheme[weight]. @scheme[font-name-directory<%>]. See also @racket[make-font]. } @defmethod[(get-face) (or/c string? false/c)]{ Gets the font's face name, or @scheme[#f] if none is specified. } @defmethod[(get-family) (one-of/c 'default 'decorative 'roman 'script 'swiss 'modern 'symbol 'system)]{ Gets the font's family. See @scheme[font%] for information about families. } @defmethod[(get-font-id) exact-integer?]{ Gets the font's ID, for use with a @scheme[font-name-directory<%>]. The ID is determined by the font's face and family specifications, only. } @defmethod[(get-point-size) (integer-in 1 255)]{ 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 @method[font% 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. } @defmethod[(get-size-in-pixels) boolean?]{ Returns @scheme[#t] if the size reported by @method[font% get-point-size] is in logical drawing units, @scheme[#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. } @defmethod[(get-smoothing) (one-of/c 'default 'partly-smoothed 'smoothed 'unsmoothed)]{ Gets the font's anti-alias smoothing mode. See @scheme[font%] for information about smoothing. } @defmethod[(get-style) (one-of/c 'normal 'italic 'slant)]{ Gets the font's slant style. See @scheme[font%] for information about styles. } @defmethod[(get-underlined) boolean?]{ Returns @scheme[#t] if the font is underlined or @scheme[#f] otherwise. } @defmethod[(get-weight) (one-of/c 'normal 'bold 'light)]{ Gets the font's weight. See @scheme[font%] for information about weights. } @defmethod[(screen-glyph-exists? [c char] [for-label? any/c #f]) boolean?]{ Returns @scheme[#t] if the given character has a corresponding glyph when drawing to the screen or a bitmap, @scheme[#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 @scheme[dc<%>] drawing. For @scheme[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 @method[dc<%> glyph-exists?] . }}