font manual page - Tk Built-In Commands

The font command provides several facilities for dealing with fonts, such as defining named fonts and inspecting the actual attributes of a font. The command has several different forms, determined by the first argument. The following forms are currently supported:

font actual font ?-displayof window? ?option? ?--? ?char?

Returns information about the actual attributes that are obtained when font is used on window's display; the actual attributes obtained may differ from the attributes requested due to platform-dependent limitations, such as the availability of font families and point sizes. font is a font description; see FONT DESCRIPTIONS below. If the window argument is omitted, it defaults to the main window. If option is specified, returns the value of that attribute; if it is omitted, the return value is a list of all the attributes and their values. See FONT OPTIONS below for a list of the possible attributes. If the char argument is supplied, it must be a single character. The font attributes returned will be those of the specific font used to render that character, which will be different from the base font if the base font does not contain the given character. If char may be a hyphen, it should be preceded by -- to distinguish it from a misspelled option.

font configure fontname ?option? ?value option value ...?

Query or modify the desired attributes for the named font called fontname. If no option is specified, returns a list describing all the options and their values for fontname. If a single option is specified with no value, then returns the current value of that attribute. If one or more option-value pairs are specified, then the command modifies the given named font to have the given values; in this case, all widgets using that font will redisplay themselves using the new attributes for the font. See FONT OPTIONS below for a list of the possible attributes.

Note that on Aqua/Mac OS X, the system fonts (see PLATFORM SPECIFIC FONTS below) may not be actually altered because they are implemented by the system theme. To achieve the effect of modification, use font actual to get their configuration and font create to synthesize a copy of the font which can be modified.

font create ?fontname? ?option value ...?

Creates a new named font and returns its name. fontname specifies the name for the font; if it is omitted, then Tk generates a new name of the form fontx, where x is an integer. There may be any number of option-value pairs, which provide the desired attributes for the new named font. See FONT OPTIONS below for a list of the possible attributes.

font delete fontname ?fontname ...?

Delete the specified named fonts. If there are widgets using the named font, the named font will not actually be deleted until all the instances are released. Those widgets will continue to display using the last known values for the named font. If a deleted named font is subsequently recreated with another call to font create, the widgets will use the new named font and redisplay themselves using the new attributes of that font.

font families ?-displayof window?

The return value is a list of the case-insensitive names of all font families that exist on window's display. If the window argument is omitted, it defaults to the main window.

font measure font ?-displayof window? text

Measures the amount of space the string text would use in the given font when displayed in window. font is a font description; see FONT DESCRIPTIONS below. If the window argument is omitted, it defaults to the main window. The return value is the total width in pixels of text, not including the extra pixels used by highly exaggerated characters such as cursive “f”. If the string contains newlines or tabs, those characters are not expanded or treated specially when measuring the string.

font metrics font ?-displayof window? ?option?

Returns information about the metrics (the font-specific data), for font when it is used on window's display. font is a font description; see FONT DESCRIPTIONS below. If the window argument is omitted, it defaults to the main window. If option is specified, returns the value of that metric; if it is omitted, the return value is a list of all the metrics and their values. See FONT METRICS below for a list of the possible metrics.

font names

The return value is a list of all the named fonts that are currently defined.

FONT DESCRIPTIONS

The following formats are accepted as a font description anywhere font is specified as an argument above; these same forms are also permitted when specifying the -font option for widgets.

[1] fontname

The name of a named font, created using the font create command. When a widget uses a named font, it is guaranteed that this will never cause an error, as long as the named font exists, no matter what potentially invalid or meaningless set of attributes the named font has. If the named font cannot be displayed with exactly the specified attributes, some other close font will be substituted automatically.

[2] systemfont

The platform-specific name of a font, interpreted by the graphics server. This also includes, under X, an XLFD (see [4]) for which a single “*” character was used to elide more than one field in the middle of the name. See PLATFORM SPECIFIC FONTS for a list of the system fonts.

[3] family ?size? ?style? ?style ...?

A properly formed list whose first element is the desired font family and whose optional second element is the desired size. The interpretation of the size attribute follows the same rules described for -size in FONT OPTIONS below. Any additional optional arguments following the size are font styles. Possible values for the style arguments are as follows:

normal	bold	roman	italic
underline	overstrike

[4] X-font names (XLFD)

A Unix-centric font name of the form -foundry-family-weight-slant-setwidth-addstyle-pixel-point-resx-resy-spacing-width-charset-encoding. The “*” character may be used to skip individual fields that the user does not care about. There must be exactly one “*” for each field skipped, except that a “*” at the end of the XLFD skips any remaining fields; the shortest valid XLFD is simply “*”, signifying all fields as defaults. Any fields that were skipped are given default values. For compatibility, an XLFD always chooses a font of the specified pixel size (not point size); although this interpretation is not strictly correct, all existing applications using XLFDs assumed that one “point” was in fact one pixel and would display incorrectly (generally larger) if the correct size font were actually used.

[5] option value ?option value ...?

A properly formed list of option-value pairs that specify the desired attributes of the font, in the same format used when defining a named font; see FONT OPTIONS below.

When font description font is used, the system attempts to parse the description according to each of the above five rules, in the order specified. Cases [1] and [2] must match the name of an existing named font or of a system font. Cases [3], [4], and [5] are accepted on all platforms and the closest available font will be used. In some situations it may not be possible to find any close font (e.g., the font family was a garbage value); in that case, some system-dependent default font is chosen. If the font description does not match any of the above patterns, an error is generated.

FONT METRICS

The following options are used by the font metrics command to query font-specific data determined when the font was created. These properties are for the whole font itself and not for individual characters drawn in that font. In the following definitions, the “baseline” of a font is the horizontal line where the bottom of most letters line up; certain letters, such as lower-case “g” stick below the baseline.

-ascent: The amount in pixels that the tallest letter sticks up above the baseline of the font, plus any extra blank space added by the designer of the font.
-descent: The largest amount in pixels that any letter sticks down below the baseline of the font, plus any extra blank space added by the designer of the font.
-linespace: Returns how far apart vertically in pixels two lines of text using the same font should be placed so that none of the characters in one line overlap any of the characters in the other line. This is generally the sum of the ascent above the baseline line plus the descent below the baseline.
-fixed: Returns a boolean flag that is “1” if this is a fixed-width font, where each normal character is the same width as all the other characters, or is “0” if this is a proportionally-spaced font, where individual characters have different widths. The widths of control characters, tab characters, and other non-printing characters are not included when calculating this value.

FONT OPTIONS

The following options are supported on all platforms, and are used when constructing a named font or when specifying a font using style [5] as above:

-family name

The case-insensitive font family name. Tk guarantees to support the font families named Courier (a monospaced “typewriter” font), Times (a serifed “newspaper” font), and Helvetica (a sans-serif “European” font). The most closely matching native font family will automatically be substituted when one of the above font families is used. The name may also be the name of a native, platform-specific font family; in that case it will work as desired on one platform but may not display correctly on other platforms. If the family is unspecified or unrecognized, a platform-specific default font will be chosen.

-size size

The desired size of the font. If the size argument is a positive number, it is interpreted as a size in points. If size is a negative number, its absolute value is interpreted as a size in pixels. If a font cannot be displayed at the specified size, a nearby size will be chosen. If size is unspecified or zero, a platform-dependent default size will be chosen.

Sizes should normally be specified in points so the application will remain the same ruler size on the screen, even when changing screen resolutions or moving scripts across platforms. However, specifying pixels is useful in certain circumstances such as when a piece of text must line up with respect to a fixed-size bitmap. The mapping between points and pixels is set when the application starts, based on properties of the installed monitor, but it can be overridden by calling the tk scaling command.

-weight weight

The nominal thickness of the characters in the font. The value normal specifies a normal weight font, while bold specifies a bold font. The closest available weight to the one specified will be chosen. The default weight is normal.

-slant slant

The amount the characters in the font are slanted away from the vertical. Valid values for slant are roman and italic. A roman font is the normal, upright appearance of a font, while an italic font is one that is tilted some number of degrees from upright. The closest available slant to the one specified will be chosen. The default slant is roman.

-underline boolean

The value is a boolean flag that specifies whether characters in this font should be underlined. The default value for underline is false.

-overstrike boolean

The value is a boolean flag that specifies whether a horizontal line should be drawn through the middle of characters in this font. The default value for overstrike is false.

STANDARD FONTS

The following named fonts are supported on all systems, and default to values that match appropriate system defaults.

TkDefaultFont: This font is the default for all GUI items not otherwise specified.
TkTextFont: This font should be used for user text in entry widgets, listboxes etc.
TkFixedFont: This font is the standard fixed-width font.
TkMenuFont: This font is used for menu items.
TkHeadingFont: This font should be used for column headings in lists and tables.
TkCaptionFont: This font should be used for window and dialog caption bars.
TkSmallCaptionFont: This font should be used for captions on contained windows or tool dialogs.
TkIconFont: This font should be used for icon captions.
TkTooltipFont: This font should be used for tooltip windows (transient information windows).

It is not advised to change these fonts, as they may be modified by Tk itself in response to system changes. Instead, make a copy of the font and modify that.

PLATFORM SPECIFIC FONTS

The following system fonts are supported:

X Windows

All valid X font names, including those listed by xlsfonts(1), are available.

MS Windows

The following fonts are supported, and are mapped to the user's style defaults.

system	ansi	device
systemfixed	ansifixed	oemfixed

Mac OS X

The following fonts are supported, and are mapped to the user's style defaults.

system

application

menu

Additionally, the following named fonts provide access to the Aqua theme fonts:

systemSystemFont	systemEmphasizedSystemFont
systemSmallSystemFont	systemSmallEmphasizedSystemFont
systemApplicationFont	systemLabelFont
systemViewsFont	systemMenuTitleFont
systemMenuItemFont	systemMenuItemMarkFont
systemMenuItemCmdKeyFont	systemWindowTitleFont
systemPushButtonFont	systemUtilityWindowTitleFont
systemAlertHeaderFont	systemToolbarFont
systemMiniSystemFont	systemDetailSystemFont
systemDetailEmphasizedSystemFont

EXAMPLE

Fill a text widget with lots of font demonstrators, one for every font family installed on your system:

pack [text .t -wrap none] -fill both -expand 1
set count 0
set tabwidth 0
foreach family [lsort -dictionary [font families]] {
    .t tag configure f[incr count] -font [list $family 10]
    .t insert end ${family}:\t {} \
            "This is a simple sampler\n" f$count
    set w [font measure [.t cget -font] ${family}:]
    if {$w+5 > $tabwidth} {
        set tabwidth [expr {$w+5}]
        .t configure -tabs $tabwidth
    }
}

KEYWORDS

font