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Font(3)               User Contributed Perl Documentation              Font(3)




NAME

       Tk::Font - Create and inspect fonts.


SYNOPSIS

           $widget->Font(option?, arg, arg, ...?)

           $font->Option?(arg, arg, ...)?


DESCRIPTION

       The Font method 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(-option?)
       $widget->fontActual(font?, -option?)
           Returns information about the actual attributes that are obtained
           when font is used on $font's display; the actual attributes
           obtained may differ from the attributes requested due to platform-
           dependant limitations, such as the availability of font families
           and pointsizes.  font is a font description; see "FONT DESCRIPTION"
           below.  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.

       $font->configure(-option??=>value, -option=>value, ...?)
           Query or modify the desired attributes for $font.  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 method 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: the above behaviour differs in detail to configure on
           widgets, images etc.

       $font = $widget->Font(-option=>value, ...>?)
       $font = $widget->fontCreate(?fontname??, -option=>value, ...>?)
           Creates a new font object and returns a reference to it.  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.

           Note: the created font is not shared between widgets of different
           MainWindows.

       $font->delete
       $widget->fontDelete(fontname?, fontname, ...?)
           Delete the specified named fonts.  If there are widgets using the
           named font, the named font won't 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 fontCreate, the
           widgets will use the new named font and redisplay themselves using
           the new attributes of that font.

       $widget->fontFamilies
           The return value is a list of the case-insensitive names of all
           font families that exist on $widget's display.

       $font->measure(text)
       $widget->fontMeasure(font, text)
           Measures the amount of space the string text would use in the given
           font when displayed in $widget.  font is a font description; see
           "FONT DESCRIPTION" below.  The return value is the total width in
           pixels of text, not including the extra pixels used by highly
           exagerrated 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(-option?)
       $widget->fontMetrics(font?, -option?)
           Returns information about the metrics (the font-specific data), for
           font when it is used on $widget's display.  font is a font
           description; see "FONT DESCRIPTION" below.  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.

       $widget->fontNames
           The return value is a list of all font objects that are currently
           defined for $widget's MainWindow.


FONT DESCRIPTION

       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 fontCreate method.
           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.

       [1a] $font
           A font object created using the Font method. This is essentially
           the same as using a named font. The object is a reference to the
           name, and carries additional information e.g. which MainWindow it
           relates to in an manner peculiar to perl/Tk.

       [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 ISSUES" 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-dependant
       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 metrics/fontMetrics method 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.  ($font->ascent is provided for
           compatibility.)

       -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.  ($font->descent is provided for
           compatibility.)

       -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 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.

           The original Tcl/Tk authors believe 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. While this is an admirable goal it does
           not work as well in practice as they hoped.  The mapping between
           points and  pixels is set when the application starts, based on
           alleged properties of the installed monitor, but it can be
           overridden by calling the  scaling command. However this can be
           problematic when system has no way of telling if (say) an 11" or
           22" monitor is attached, also if it can tell then some monitor
           sizes may result in poorer quality scaled fonts being used rather
           than a "tuned" bitmap font.  In addition specifying pixels is
           useful in certain circumstances such as when a piece of text must
           line up with respect to a fixed-size bitmap.

           At present the Tcl/Tk scheme is used unchanged, with "point" size
           being returned by actual (as an integer), and used internally.
           Suggestions for work-rounds to undesirable behaviour welcome.

       -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.


PLATFORM-SPECIFIC ISSUES

       The following named system fonts are supported:

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

       MS Windows:
            system       ansi       device
            systemfixed  ansifixed  oemfixed

       Macintosh:
            system       application


COMPATIBILITY WITH PREVIOUS VERSIONS

       In prior versions of perl/Tk the $widget->Font method was a perl
       wrapper on the original "[4] X-font names (XLFD)" style as described
       above (which was the only form supported by versions of core tk prior
       to version tk8.0).  This module is provided in its original form (it
       has just been renamed) via:

        use Tk::X11Font;
        I<$widget>-E<gt>B<X11Font>(...)

       However the methods of the old scheme have been mimiced as closely as
       possible with the new scheme. It is intended that code should work
       without modification, except for the case of using :

         @names = $font->Name;

       i.e. the Name method in an array/list context. This now returns one
       element on all platforms (as it did on Win32), while previously on X
       systems it returned a list of fonts that matched an under-specified
       pattern.

       Briefly the methods supported for compatibilty are as follows:

       $newfont = $font->Clone(-option=>value, ...>?)
           Returns a new font object $newfont related to the original $font by
           changing the values of the specified -options.

       $font->Family - maps to -family
       $font->Weight - maps to -weight
       $font->Slant - maps to -slant
       $font->Pixel and Point - map to -size

       New code should use $font->configure to achieve same effect as last
       four items above.

       Foundry, Swidth, Adstyle, Xres, Yres, Space, Avgwidth, Registry,
       Encoding
           Are all ignored if set, and return '*' if queried.

       $font->Name
           Returns the name of a named font, or a string representation of an
           unnamed font. Using $font in a scalar context does the same. Note
           this is distinctly different from behaviour of X11Font's Name in a
           list context.

       $font->Pattern
           Returns a XLFD string for the font based on actual values, and some
           heuristics to map Tk's forms to the "standard" X conventions.


SEE ALSO

       Tk::options

       Tk::X11Font


KEYWORDS

       font



perl v5.18.0                      2013-05-17                           Font(3)

perl-Tk 804.030_502 - Generated Tue Aug 13 05:59:27 CDT 2013
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