1Font(3)               User Contributed Perl Documentation              Font(3)
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NAME

6       Tk::Font - Create and inspect fonts.
7

SYNOPSIS

9           $widget->Font(option?, arg, arg, ...?)
10
11           $font->Option?(arg, arg, ...)?
12

DESCRIPTION

14       The Font method provides several facilities for dealing with fonts,
15       such as defining named fonts and inspecting the actual attributes of a
16       font.  The command has several different forms, determined by the first
17       argument.  The following forms are currently supported:
18
19       $font->actual(-option?)
20       $widget->fontActual(font?, -option?)
21           Returns information about the actual attributes that are obtained
22           when font is used on $font's display; the actual attributes
23           obtained may differ from the attributes requested due to platform-
24           dependant limitations, such as the availability of font families
25           and pointsizes.  font is a font description; see "FONT DESCRIPTION"
26           below.  If option is specified, returns the value of that
27           attribute; if it is omitted, the return value is a list of all the
28           attributes and their values.  See "FONT OPTIONS" below for a list
29           of the possible attributes.
30
31       $font->configure(-option??=>value, -option=>value, ...?)
32           Query or modify the desired attributes for $font.  If no -option is
33           specified, returns a list describing all the options and their
34           values for fontname.  If a single -option is specified with no
35           value, then returns the current value of that attribute.  If one or
36           more option-value pairs are specified, then the method modifies the
37           given named font to have the given values; in this case, all
38           widgets using that font will redisplay themselves using the new
39           attributes for the font.  See "FONT OPTIONS" below for a list of
40           the possible attributes.
41
42           Note: the above behaviour differs in detail to configure on
43           widgets, images etc.
44
45       $font = $widget->Font(-option=>value, ...>?)
46       $font = $widget->fontCreate(?fontname??, -option=>value, ...>?)
47           Creates a new font object and returns a reference to it.  fontname
48           specifies the name for the font; if it is omitted, then Tk
49           generates a new name of the form fontx, where x is an integer.
50           There may be any number of option-value pairs, which provide the
51           desired attributes for the new named font.  See "FONT OPTIONS"
52           below for a list of the possible attributes.
53
54           Note: the created font is not shared between widgets of different
55           MainWindows.
56
57       $font->delete
58       $widget->fontDelete(fontname?, fontname, ...?)
59           Delete the specified named fonts.  If there are widgets using the
60           named font, the named font won't actually be deleted until all the
61           instances are released.  Those widgets will continue to display
62           using the last known values for the named font.  If a deleted named
63           font is subsequently recreated with another call to fontCreate, the
64           widgets will use the new named font and redisplay themselves using
65           the new attributes of that font.
66
67       $widget->fontFamilies
68           The return value is a list of the case-insensitive names of all
69           font families that exist on $widget's display.
70
71       $font->measure(text)
72       $widget->fontMeasure(font, text)
73           Measures the amount of space the string text would use in the given
74           font when displayed in $widget.  font is a font description; see
75           "FONT DESCRIPTION" below.  The return value is the total width in
76           pixels of text, not including the extra pixels used by highly
77           exagerrated characters such as cursive ``f''.  If the string
78           contains newlines or tabs, those characters are not expanded or
79           treated specially when measuring the string.
80
81       $font->metrics(-option?)
82       $widget->fontMetrics(font?, -option?)
83           Returns information about the metrics (the font-specific data), for
84           font when it is used on $widget's display.  font is a font
85           description; see "FONT DESCRIPTION" below.  If option is specified,
86           returns the value of that metric; if it is omitted, the return
87           value is a list of all the metrics and their values.  See "FONT
88           METRICS" below for a list of the possible metrics.
89
90       $widget->fontNames
91           The return value is a list of all font objects that are currently
92           defined for $widget's MainWindow.
93

FONT DESCRIPTION

95       The following formats are accepted as a font description anywhere font
96       is specified as an argument above; these same forms are also permitted
97       when specifying the -font option for widgets.
98
99       [1] fontname
100           The name of a named font, created using the fontCreate method.
101           When a widget uses a named font, it is guaranteed that this will
102           never cause an error, as long as the named font exists, no matter
103           what potentially invalid or meaningless set of attributes the named
104           font has.  If the named font cannot be displayed with exactly the
105           specified attributes, some other close font will be substituted
106           automatically.
107
108       [1a] $font
109           A font object created using the Font method. This is essentially
110           the same as using a named font. The object is a reference to the
111           name, and carries additional information e.g. which MainWindow it
112           relates to in an manner peculiar to perl/Tk.
113
114       [2] systemfont
115           The platform-specific name of a font, interpreted by the graphics
116           server.  This also includes, under X, an XLFD (see [4]) for which a
117           single ``*'' character was used to elide more than one field in the
118           middle of the name.  See "PLATFORM-SPECIFIC ISSUES" for a list of
119           the system fonts.
120
121       [3] [family,?size,??style,??style ...?]
122           A properly formed list whose first element is the desired font
123           family and whose optional second element is the desired size.  The
124           interpretation of the size attribute follows the same rules
125           described for -size in "FONT OPTIONS" below.  Any additional
126           optional arguments following the size are font styles.  Possible
127           values for the style arguments are as follows:
128
129               normal      bold    roman   italic
130               underline   overstrike
131
132       [4] X-font names (XLFD)
133           A Unix-centric font name of the form
134           -foundry-family-weight-slant-setwidth-addstyle-pixel-point-resx-resy-spacing-width-charset-encoding.
135           The ``*'' character may be used to skip individual fields that the
136           user does not care about.  There must be exactly one ``*'' for each
137           field skipped, except that a ``*'' at the end of the XLFD skips any
138           remaining fields; the shortest valid XLFD is simply ``*'',
139           signifying all fields as defaults.  Any fields that were skipped
140           are given default values.  For compatibility, an XLFD always
141           chooses a font of the specified pixel size (not point size);
142           although this interpretation is not strictly correct, all existing
143           applications using XLFDs assumed that one ``point'' was in fact one
144           pixel and would display incorrectly (generally larger) if the
145           correct size font were actually used.
146
147       [5] option value ?option value ...?
148           A properly formed list of option-value pairs that specify the
149           desired attributes of the font, in the same format used when
150           defining a named font; see "FONT OPTIONS" below.
151
152       When font description font is used, the system attempts to parse the
153       description according to each of the above five rules, in the order
154       specified.  Cases [1] and [2] must match the name of an existing named
155       font or of a system font.  Cases [3], [4], and [5] are accepted on all
156       platforms and the closest available font will be used.  In some
157       situations it may not be possible to find any close font (e.g., the
158       font family was a garbage value); in that case, some system-dependant
159       default font is chosen.  If the font description does not match any of
160       the above patterns, an error is generated.
161

FONT METRICS

163       The following options are used by the metrics/fontMetrics method to
164       query font-specific data determined when the font was created.  These
165       properties are for the whole font itself and not for individual
166       characters drawn in that font.  In the following definitions, the
167       ``baseline'' of a font is the horizontal line where the bottom of most
168       letters line up; certain letters, such as lower-case ``g'' stick below
169       the baseline.
170
171       -ascent
172           The amount in pixels that the tallest letter sticks up above the
173           baseline of the font, plus any extra blank space added by the
174           designer of the font.  ($font->ascent is provided for
175           compatibility.)
176
177       -descent
178           The largest amount in pixels that any letter sticks down below the
179           baseline of the font, plus any extra blank space added by the
180           designer of the font.  ($font->descent is provided for
181           compatibility.)
182
183       -linespace
184           Returns how far apart vertically in pixels two lines of text using
185           the same font should be placed so that none of the characters in
186           one line overlap any of the characters in the other line.  This is
187           generally the sum of the ascent above the baseline line plus the
188           descent below the baseline.
189
190       -fixed
191           Returns a boolean flag that is ``1'' if this is a fixed-width font,
192           where each normal character is the the same width as all the other
193           characters, or is ``0'' if this is a proportionally-spaced font,
194           where individual characters have different widths.  The widths of
195           control characters, tab characters, and other non-printing
196           characters are not included when calculating this value.
197

FONT OPTIONS

199       The following options are supported on all platforms, and are used when
200       constructing a named font or when specifying a font using style [5] as
201       above:
202
203       -family => name
204           The case-insensitive font family name.  Tk guarantees to support
205           the font families named Courier (a monospaced ``typewriter'' font),
206           Times (a serifed ``newspaper'' font), and Helvetica (a sans-serif
207           ``European'' font).  The most closely matching native font family
208           will automatically be substituted when one of the above font
209           families is used.  The name may also be the name of a native,
210           platform-specific font family; in that case it will work as desired
211           on one platform but may not display correctly on other platforms.
212           If the family is unspecified or unrecognized, a platform-specific
213           default font will be chosen.
214
215       -size => size
216           The desired size of the font.  If the size argument is a positive
217           number, it is interpreted as a size in points.  If size is a
218           negative number, its absolute value is interpreted as a size in
219           pixels.  If a font cannot be displayed at the specified size, a
220           nearby size will be chosen.  If size is unspecified or zero, a
221           platform-dependent default size will be chosen.
222
223           The original Tcl/Tk authors believe sizes should normally be
224           specified in points so the application will remain the same ruler
225           size on the screen, even when changing screen resolutions or moving
226           scripts across platforms. While this is an admirable goal it does
227           not work as well in practice as they hoped.  The mapping between
228           points and  pixels is set when the application starts, based on
229           alleged properties of the installed monitor, but it can be
230           overridden by calling the  scaling command. However this can be
231           problematic when system has no way of telling if (say) an 11" or
232           22" monitor is attached, also if it can tell then some monitor
233           sizes may result in poorer quality scaled fonts being used rather
234           than a "tuned" bitmap font.  In addition specifying pixels is
235           useful in certain circumstances such as when a piece of text must
236           line up with respect to a fixed-size bitmap.
237
238           At present the Tcl/Tk scheme is used unchanged, with "point" size
239           being returned by actual (as an integer), and used internally.
240           Suggestions for work-rounds to undesirable behaviour welcome.
241
242       -weight => weight
243           The nominal thickness of the characters in the font.  The value
244           normal specifies a normal weight font, while bold specifies a bold
245           font.  The closest available weight to the one specified will be
246           chosen.  The default weight is normal.
247
248       -slant => slant
249           The amount the characters in the font are slanted away from the
250           vertical.  Valid values for slant are roman and italic.  A roman
251           font is the normal, upright appearance of a font, while an italic
252           font is one that is tilted some number of degrees from upright.
253           The closest available slant to the one specified will be chosen.
254           The default slant is roman.
255
256       -underline => boolean
257           The value is a boolean flag that specifies whether characters in
258           this font should be underlined.  The default value for underline is
259           false.
260
261       -overstrike => boolean
262           The value is a boolean flag that specifies whether a horizontal
263           line should be drawn through the middle of characters in this font.
264           The default value for overstrike is false.
265

PLATFORM-SPECIFIC ISSUES

267       The following named system fonts are supported:
268
269       X Windows:
270           All valid X font names, including those listed by xlsfonts(1), are
271           available.
272
273       MS Windows:
274            system       ansi       device
275            systemfixed  ansifixed  oemfixed
276
277       Macintosh:
278            system       application
279

COMPATIBILITY WITH PREVIOUS VERSIONS

281       In prior versions of perl/Tk the $widget->Font method was a perl
282       wrapper on the original "[4] X-font names (XLFD)" style as described
283       above (which was the only form supported by versions of core tk prior
284       to version tk8.0).  This module is provided in its original form (it
285       has just been renamed) via:
286
287        use Tk::X11Font;
288        I<$widget>-E<gt>B<X11Font>(...)
289
290       However the methods of the old scheme have been mimiced as closely as
291       possible with the new scheme. It is intended that code should work
292       without modification, except for the case of using :
293
294         @names = $font->Name;
295
296       i.e. the Name method in an array/list context. This now returns one
297       element on all platforms (as it did on Win32), while previously on X
298       systems it returned a list of fonts that matched an under-specified
299       pattern.
300
301       Briefly the methods supported for compatibilty are as follows:
302
303       $newfont = $font->Clone(-option=>value, ...>?)
304           Returns a new font object $newfont related to the original $font by
305           changing the values of the specified -options.
306
307       $font->Family - maps to -family
308       $font->Weight - maps to -weight
309       $font->Slant - maps to -slant
310       $font->Pixel and Point - map to -size
311
312       New code should use $font->configure to achieve same effect as last
313       four items above.
314
315       Foundry, Swidth, Adstyle, Xres, Yres, Space, Avgwidth, Registry,
316       Encoding
317           Are all ignored if set, and return '*' if queried.
318
319       $font->Name
320           Returns the name of a named font, or a string representation of an
321           unnamed font. Using $font in a scalar context does the same. Note
322           this is distinctly different from behaviour of X11Font's Name in a
323           list context.
324
325       $font->Pattern
326           Returns a XLFD string for the font based on actual values, and some
327           heuristics to map Tk's forms to the "standard" X conventions.
328

SEE ALSO

330       Tk::options
331
332       Tk::X11Font
333

KEYWORDS

335       font
336
337
338
339perl v5.28.0                      2018-07-15                           Font(3)
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