17 Fonts
Contents
17.1 Introduction
Reliable delivery of fonts is a requirement for SVG.
Designers need to create SVG content with arbitrary fonts and
know that the same graphical result will appear when the
content is viewed by all end users, even when end users do not
have the necessary fonts installed on their computers. This
parallels the print world, where the designer uses a given font
when authoring a drawing for print, and the graphical content
appears exactly the same in the printed version as it appeared
on the designer's authoring system.
Historically, one approach has been to convert all text to paths
representing the glyphs used. This preserves the visual look, but means
that the text is lost; it cannot be dynamically updated and is not accessible.
Another approach is to hope that a font with a given name is available
to all renderers. This assumption does not work well on the desktop
and works very badly in a heterogeneous mobile environment.
SVG solves this problem by allowing the text to be converted to
paths, but storing those paths as an SVG font. The text is retained
and remains dynamically modifiable and accessible.
17.1.1 Describing fonts available to SVG
SVG utilizes an XML version of the WebFonts
facility defined in the "Cascading Style Sheets (CSS) level 2"
specification [CSS2] to reference fonts.
Described fonts may be in a variety of different formats. By describing key
details of the font such as its family name, weight, whether it is italic and so on,
text can continue to use the font properties without having to explicitly indicate
the font that is to be used for each span of text.
17.1.2 Defining fonts in SVG
One disadvantage to the WebFont
facility to date is that specifications such as [CSS2] do not require
support of particular font formats. The result is that
different implementations support different Web font formats,
thereby making it difficult for Web site creators to post a
single Web site using WebFonts that work across all user
agents.
To provide a common font format for SVG that is guaranteed
to be supported by all conforming SVG
viewers, SVG also defines a font format, in SVG, which uses the same geometric
mechanism for glyphs as is used by the SVG path element.
This facility is called SVG
fonts. SVG implementations must support the SVG font format, and may also support other formats. WebFonts
may be contained in the SVG document which uses them, or stored in a
separate document (for example, to allow sharing of the same font by multiple SVG documents).
Taken together, these two mechanisms ensure reliable delivery of
font data to end users, preserving graphical richness and enabling accessible access to the textual data.
In a
common scenario, SVG authoring applications generate
compressed, subsetted WebFonts
for all text elements used by a given SVG document fragment.
SVG fonts can improve the semantic richness of graphics that
represent text. For example, many company logos consist of the
company name drawn artistically. In some cases, accessibility may be enhanced by
expressing the logo as a series of glyphs in an SVG font and
then rendering the logo as a 'text' element which references
this font.
17.2 Overview of SVG fonts
An SVG font is a font defined
using SVG's 'font' element.
The purpose of SVG fonts is to allow for delivery of glyph
outlines in display-only environments. SVG fonts that accompany
Web pages must be supported only in browsing and viewing
situations. Graphics editing applications or file translation
tools must not attempt to convert SVG fonts into system fonts.
SVG fonts contain unhinted font outlines. Because of this,
on many implementations there will be limitations regarding the
quality and legibility of text in small font sizes. For
increased quality and legibility in small font sizes, content
creators may want to use an alternate font technology, such as
fonts that ship with operating systems or an alternate WebFont
format.
Because SVG fonts are expressed using SVG elements and
attributes, in some cases the SVG font will take up more space
than if the font were expressed in a different
format which was especially designed for compact expression of
font data. For the fastest delivery of Web pages, content
creators may want to use an alternate font technology as
a first choice, with a fallback to an SVG font for interoperability.
A key value of SVG fonts is guaranteed availability in SVG
user agents. In some situations, it might be appropriate for an
SVG font to be the first choice for rendering some text. In
other situations, the SVG font might be an alternate, back-up
font in case the first choice font (perhaps a hinted system
font) is not available to a given user.
The characteristics and attributes of SVG fonts correspond
closely to the font characteristics and parameters described in
the "Fonts"
chapter of the "Cascading Style Sheets (CSS) level 2"
specification [CSS2]. In this model,
various font metrics, such as advance values and baseline
locations, and the glyph outlines themselves, are expressed in
units that are relative to an abstract square whose height is
the intended distance between lines of type in the same type
size. This square is called the em
square and it is the design grid on which the glyph
outlines are defined. The value of the 'units-per-em' attribute on the 'font' element specifies how
many units the em square is divided into. Common values for
other font types are, for example, 250 (Intellifont), 1000
(Type 1) and 2048 (TrueType, TrueType GX and Open-Type). Unlike
standard graphics in SVG, where the initial coordinate system
has the y-axis pointing downward (see The initial
coordinate system), the design grid for SVG fonts, along
with the initial coordinate system for the glyphs, has the
y-axis pointing upward for consistency with accepted industry
practice for many popular font formats.
SVG fonts and their associated glyphs do not specify
bounding box information. Because the glyph outlines are
expressed as SVG path elements, the implementation has the
option to render the glyphs either using standard graphics
calls or by using special-purpose font rendering technology, in
which case any necessary maximum bounding box and overhang
calculations can be performed from analysis of the path
elements contained within the glyph outlines.
An SVG font can be either embedded within the same document
that uses the font or saved as part of an external
resource.
Here is an example of how you might embed an SVG font inside
of an SVG document.
<?xml version="1.0"?>
<svg width="400px" height="300px" version="1.2" baseProfile="tiny"
xmlns = 'http://www.w3.org/2000/svg'>
<defs>
<font xml:id="Font1" horiz-adv-x="1000">
<font-face font-family="Super Sans" font-weight="bold" font-style="normal"
units-per-em="1000" cap-height="600" x-height="400"
ascent="700" descent="300" alphabetic="0" mathematical="350" ideographic="400" hanging="500">
</font-face>
<missing-glyph d="M0,0h200v200h-200z"/>
<glyph unicode="!" horiz-adv-x="300" d="--Outline of exclam. pt. glyph--"/>
<glyph unicode="@" d="--Outline of @ glyph--"/>
<!-- more glyphs -->
</font>
</defs>
<desc>An example using an embedded font.</desc>
<text x="100" y="100" font-family="Super Sans, Helvetica, sans-serif"
font-weight="bold" font-style="normal">Text
using embedded font</text>
</svg>
17.3 The 'font'
element
The 'font' element defines
an SVG font.
Attribute definitions:
- horiz-origin-x = "<number>"
The X-coordinate in the font coordinate system of the
origin of a glyph to be used when drawing horizontally
oriented text. (Note that the origin applies to all glyphs
in the font.)
The lacuna value
is '0'.
Animatable:
no.
- horiz-adv-x = "<number>"
The default horizontal advance after rendering a glyph
in horizontal orientation. Glyph widths are required to be
non-negative, even if the glyph is typically rendered
right-to-left, as in Hebrew and Arabic scripts.
The lacuna value
is '0'.
Animatable:
no.
Each 'font' element must
have a 'font-face' child element which
describes various characteristics of the font.
17.4 The 'glyph'
element
The 'glyph' element
defines the graphics for a given glyph. The coordinate system
for the glyph is defined by the various attributes in the 'font' element.
The graphics that make up the 'glyph' consist of a single path data specification within
the 'd' attribute.
Attribute definitions:
- unicode = "<string>"
One or more characters indicating the sequence
of characters which corresponds to this glyph. If a
single character is provided, then this glyph corresponds to the
given Unicode character. If multiple characters are
provided, then this glyph corresponds to the given sequence
of Unicode characters. One use of a sequence of characters
is ligatures. For example, if unicode="ffl", then the given
glyph will be used to render the sequence of characters
"f", "f", and "l".
It is often useful to refer to characters using XML
character references expressed in hexadecimal notation or
decimal notation. For example, unicode="ffl" could be expressed
as XML character references in hexadecimal notation as
unicode="ffl"
or in decimal notation as unicode="ffl".
The 'unicode' attribute
contributes to the process for deciding which glyph(s) are
used to represent which character(s). See glyph selection
rules. If the 'unicode' attribute is not
provided for a given 'glyph', the glyph cannot be accessed in SVG Tiny 1.2.
Animatable:
no.
- glyph-name = "<list-of-strings>"
An optional name for the glyph. Glyph names should be unique within a font.
The glyph names can be used
in situations where Unicode character numbers do not
provide sufficient information to access the correct glyph,
such as when there are multiple glyphs per Unicode
character. The glyph names can be referenced in kerning
definitions.
Animatable:
no.
- d = "path
data"
The definition of the outline of a glyph, using the
same syntax as for the 'd' attribute on a 'path' element. See Path data.
See below for a discussion of this attribute.
Animatable:
no.
- arabic-form = "initial | medial | terminal | isolated"
For Arabic glyphs, indicates which of the four possible
forms this glyph represents.If arabic-form is not specified for
a glyph that requires it, the glyph is taken to be the isolated form
and the initial, medial, and terminal forms will render with missing-glyph
unless separately specified.
Additionally, if initial, medial, or terminal are specified on a glyph
that does not require the arabic-form to be specified, the arabic-form
attribute shall have no effect.
Animatable:
no.
- lang = "<list-of-language-ids>"
The attribute value is a comma-separated list of language tags
as defined in IETF Best Current Practice 47
[BCP47].
For XML content, the glyph can be used if the 'xml:lang' attribute exactly matches one of the languages given in the value of this parameter, or if the 'xml:lang' attribute exactly equals a prefix of one of the languages given in the value of this parameter such that the first tag character following the prefix is "-". If the attribute is not specified, then the glyph can be used in all languages.
For example, a glyph suitable for French (whose lang attribute
includes the language tag 'fr') is suitable for all types of
French text (for example, Canadian French, xml:lang="fr-ca"). A
glyph whose lang attribute is specific for Traditional Chinese
(lang includes zh-Hant) is not suitable for Simplified Chinese
(xml:lang="zh-Hanc") or generic Chinese (xml:lang="zh").
Animatable:
no.
- horiz-adv-x = "<number>"
The horizontal advance after rendering the glyph in
horizontal orientation. If the attribute is not specified,
the effect is as if the attribute were set to the value of
the font's 'horiz-adv-x' attribute.
Glyph widths are required to be non-negative, even if the
glyph is typically rendered right-to-left, as in Hebrew and
Arabic scripts.
Animatable:
no.
The graphics for the 'glyph' are specified using
the 'd' attribute. The path data within this attribute must be processed as follows:
Any relative coordinates within the path data
specification are converted into equivalent absolute
coordinates.
Each of these absolute coordinates is transformed from
the font coordinate system into the
text content element's current
coordinate system such that the origin of the font coordinate
system is properly positioned and rotated to align with the
current text
position and orientation for the glyph, and scaled so
that the correct 'font-size' is achieved.
The resulting, transformed path specification is rendered
as if it were a 'path' element, using the
styling properties that apply to the characters which
correspond to the given glyph, and ignoring any styling
properties specified on the 'font' element or the 'glyph' element.
In general, the 'd' attribute renders in the same
manner as system fonts. For example, a dashed pattern will
usually look the same if applied to a system font or to an SVG
font which defines its glyphs using the 'd' attribute. Many implementations
will be able to render glyphs quickly and will be
able to use a font cache for further performance gains.
Example font01 below
contains a font for just three letters - S, V, and G - plus a missing glyph for all other
characters. There is also a kern pair, to bring the V and the G glyphs closer together.
The font, Anglepoise, was
designed by Ray Larabie of Larabie Fonts and is used by permission.
<?xml version="1.0" encoding="UTF-8"?>
<svg version="1.2" baseProfile="tiny" viewBox="0 0 160 70" xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Font example</title>
<defs>
<font horiz-adv-x="313" xml:id="la">
<metadata>Converted from Larabie Anglepoise by Batik ttf2svg
See http://www.larabiefonts.com/ </metadata>
<font-face font-family="larabie-anglepoise" units-per-em="1000"
panose-1="0 0 4 0 0 0 0 0 0 0" ascent="703" descent="-300" alphabetic="0"/>
<missing-glyph horiz-adv-x="500" d="M63 0V700H438V0H63ZM125 63H375V638H125V63Z"/>
<glyph unicode="S" glyph-name="S" horiz-adv-x="385" d="M371 1H29V144H264Q264 151 264
166Q265 180 265 188Q265 212 249 212H132Q83 212 55 247Q29 279 29
329V566H335V422H136V375Q136 360 144 356Q148 355 168 355H279Q327 355 352 309Q371 273
371 221V1Z"/>
<glyph unicode="V" glyph-name="V" horiz-adv-x="351" d="M365 563L183 -33L0 563H101L183
296L270 563H365Z"/>
<glyph unicode="G" glyph-name="G" horiz-adv-x="367" d="M355
1H18V564H355V420H125V144H248V211H156V355H355V1Z"/>
<hkern g1="V" g2="G" k="-40"/>
</font>
</defs>
<text x="40" y="50" font-family="larabie-anglepoise" font-size="70" fill="#933">SVG</text>
<rect x="00" y="00" width="160" height="70" stroke="#777" fill="none"/>
</svg>
Example font02 below
contains a font for a single character, the Arabic letter خ - plus a space and missing glyph.
There are four glyphs for this character, each corresponding to the same Unicode code point U+062E.
They are distinguished by the values of the arabic-form attribute. The text string
demonstrates each of the four forms.
<?xml version="1.0" encoding="UTF-8"?>
<svg version="1.2" baseProfile="tiny" viewBox="80 100 260 180" xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Font example for arabic-form</title>
<defs>
<font horiz-adv-x="573">
<font-face font-family="SVGAr" units-per-em="1000" panose-1="5 1 1 1 1 1 1 1 1 1"
ascent="1025" descent="-399" alphabetic="0"/>
<missing-glyph horiz-adv-x="500" d="M31 0V800H469V0H31ZM438 31V769H62V31H438Z"/>
<glyph unicode=" " glyph-name="space" horiz-adv-x="370"/>
<glyph unicode="خ" glyph-name="khah-isolated" arabic-form="isolated"
horiz-adv-x="562" d="M309 360Q309 353 297 335T271 317Q260 317 227 337T194 370Q194
380 205 397T232 415Q246 415 277 395T309 360ZM518 -265Q516 -269 509 -275Q507 -277 502
-281Q447 -319 424 -330Q356 -363 281 -363Q228 -363 186 -347T110 -294Q69 -249 54
-199Q44 -167 44 -127Q44 -96 50 -65T76 12Q88 39 110 70Q152 127 152 137Q152 151 148
156T121 161Q95 161 85 156Q72 146 62 140Q44 128 35 130Q35 138 35 146Q37 151 43 162Q77
208 98 219T159 231Q170 231 234 221Q255 218 298 210H340Q347 210 382 218T425 230T435
235Q446 239 449 234Q454 226 444 189T426 152Q418 152 393 154T360 156Q327 156 297
149T228 120Q180 93 142 36Q96 -33 96 -110Q96 -209 168 -257Q223 -294 300 -294Q343 -294
371 -291Q429 -285 489 -267Q506 -260 511 -260Q514 -262 518 -265Z"/>
<glyph unicode="خ" glyph-name="khah-initial" arabic-form="initial"
horiz-adv-x="728" d="M297 372Q297 365 285 347T259 329Q248 329 215 349T182 382Q182
392 193 409T220 427Q234 427 265 407T297 372ZM600 0H0V68H373Q396 68 396 86Q396 89 394
95Q377 137 347 159Q308 188 243 188Q210 188 183 171Q165 160 157 158T145 156Q138 156
138 164L140 174Q145 196 191 220Q228 240 269 240Q313 240 355 221T447 160Q488 120 530
81Q543 73 563 71T609 68Q619 68 620 68T625 68Q645 68 645 46Q645 30 633 15T600 0Z"/>
<glyph unicode="خ" glyph-name="khah-medial" arabic-form="medial"
horiz-adv-x="625" d="M296 376Q296 369 284 351T258 333Q247 333 214 353T181 386Q181
396 192 413T219 431Q233 431 264 411T296 376ZM625 0H0V68H373Q396 68 396 86Q396 89 394
95Q377 137 347 159Q308 188 243 188Q210 188 183 171Q165 160 157 158T145 156Q138 156
138 164L140 174Q145 196 191 220Q228 240 269 240Q313 240 355 221T447 160Q488 120 530
81Q543 73 563 71T609 68Q619 68 620 68T625 68V0Z"/>
<glyph unicode="خ" glyph-name="khah-terminal" arabic-form="terminal"
horiz-adv-x="514" d="M296 352Q296 345 284 327T258 309Q247 309 214 329T181 362Q181
372 192 389T219 407Q233 407 264 387T296 352ZM514 0H375Q313 0 298 64T261 128Q209 128
153 62Q91 -12 91 -101Q91 -199 162 -243Q220 -279 319 -279Q367 -279 390 -276T463
-259Q466 -258 475 -255T488 -252Q490 -252 491 -254T489 -263Q484 -272 466 -286T433
-307Q408 -320 401 -323Q349 -344 277 -344Q169 -344 104 -274Q44 -210 44 -118Q44 -88 51
-53T73 14Q80 31 97 56Q132 108 132 118Q132 127 126 134T110 141Q92 141 85 137Q72 127
59 117Q49 112 44 112Q38 112 38 119Q38 122 40 128Q49 156 80 182Q116 212 157 212Q170
212 188 208Q232 198 258 198H320Q345 198 357 201Q374 207 383 209T398 214T412 216Q420
216 421 212Q424 202 414 170T396 137Q394 137 382 140T362 143Q346 143 337 135T327
104Q327 91 341 80T379 68H514V0Z"/>
</font>
</defs>
<g font-family="SVGAr" font-size="80">
<!-- this should produce isolated khah, followed by initial,medial and terminal khah -->
<text x="100" y="200">خ خخخ</text>
<rect x="80" y="100" width="260" height="180" fill="none" stroke="#777"/>
</g>
</svg>
17.5 The 'missing-glyph'
element
The 'missing-glyph'
element defines a graphic to use if there is an attempt to
draw a glyph from a given font and the given glyph has not been
defined. The attributes on the 'missing-glyph' element have the
same meaning as the corresponding attributes on the 'glyph' element.
17.6 Glyph selection rules
When determining the glyph(s) to draw a given character
sequence, the 'font' element must be searched from
its first 'glyph' element to its last in
logical order to see if the upcoming sequence of Unicode
characters to be rendered matches the sequence of Unicode
characters specified in the 'unicode' attribute for the given 'glyph' element. The first
successful match must be used. Thus, if an "ffl" ligature is defined in the font after the "f" glyph,
it will not be used.
17.7 The 'hkern' element
The 'hkern' element defines kerning
pairs for horizontally-oriented pairs
of glyphs.
Kern pairs identify pairs of glyphs within a single font
whose inter-glyph spacing is adjusted when the pair of glyphs
are rendered next to each other. In addition to the requirement
that the pair of glyphs are from the same font, SVG font
kerning happens only when the two glyphs correspond to
characters which have the same values for properties 'font-family', 'font-size', 'font-style' and 'font-weight'.
An example of a kerning pair are the letters "Va", where the
typographic result might look better if the letters "V" and the
"a" were rendered slightly closer together.
Right-to-left and bidirectional text in SVG is laid out in a
two-step process, which is described in Relationship
with bidirectionality. If SVG fonts are used, before
kerning is applied, characters are re-ordered into
left-to-right (or top-to-bottom, for vertical text) visual
rendering order. Kerning from SVG fonts is then applied on
pairs of glyphs which are rendered contiguously. The first
glyph in the kerning pair is the left (or top) glyph in visual
rendering order. The second glyph in the kerning pair is the
right (or bottom) glyph in the pair.
For convenience to font designers and to minimize file
sizes, a single 'hkern' can define a single
kerning adjustment value between one set of glyphs (sequences and/or ranges
of Unicode characters) and another set of glyphs (e.g.,
another range of Unicode characters).
The 'hkern' element
defines kerning pairs and adjustment values in the horizontal
advance value when drawing pairs of glyphs which the two glyphs
are contiguous and are both rendered horizontally (i.e.,
side-by-side). The spacing between characters is reduced by the
kerning adjustment. (Negative kerning adjustments increase the
spacing between characters.)
Attribute definitions:
- u1 = "[<Char> | <urange> ] [,
[<Char> | <urange>] ]* "
A sequence (comma-separated) of characters
and/or ranges of Unicode characters (see
description of ranges of Unicode characters in [CSS2]) which
identify a set of possible first glyphs in the kerning
pair. If a given Unicode character within the set has
multiple corresponding 'glyph' elements (i.e.,
there are multiple 'glyph' elements with the
same 'unicode' attribute value, but
different 'glyph-name' values), then all
such glyphs are included in the set. Comma is the separator
character; thus, to kern a comma, specify the comma as part
of a range of Unicode characters or as a glyph name using
the 'g1' attribute. The total set of
possible first glyphs in the kerning pair is the union of
glyphs specified by the 'u1' and 'g1' attributes.
Animatable:
no.
- g1 = "<list-of-strings>"
A sequence of glyph names (i.e.,
values that match 'glyph-name' attributes on 'glyph' elements) which
identify a set of possible first glyphs in the kerning
pair. All glyphs with the given glyph name are included in
the set. The total set of possible first glyphs in the
kerning pair is the union of glyphs specified by the 'u1' and 'g1' attributes.
Animatable:
no.
- u2 = "[<Char> | <urange> ] [,
[<Char> | <urange>] ]* "
Same as the 'u1' attribute, except that 'u2' specifies possible second
glyphs in the kerning pair.
Animatable:
no.
- g2 = "<list-of-strings>"
Same as the 'g1' attribute, except that 'g2' specifies possible second
glyphs in the kerning pair.
Animatable:
no.
- k = "<number>"
The amount to decrease the spacing between the two
glyphs in the kerning pair. The value is in the font
coordinate system.
The lacuna value
is '0'.
Animatable:
no.
At least one of
'u1' and
'g1' must be provided,
and at least one of
'u2' and
'g2' must be provided.
17.8 Describing a font
17.8.1 Overview of font descriptions
A font description provides the bridge between an author's
font specification and the font data, which is the data needed
to format text and to render the abstract glyphs to which the
characters map — the actual scalable outlines or bitmaps. Fonts
are referenced by properties, such as the 'font-family' property.
Each specified font description is added to the font
database so that it can be used to select the relevant font
data. The font description contains descriptors such as the
location of the font data on the Web, and characterizations of
that font data. The font descriptors are also needed to match
the font properties to particular font data. The level of
detail of a font description can vary from just the name of the
font up to a list of glyph widths.
For more about font descriptions, refer to the
Fonts chapter
in the CSS2 specification [CSS2].
17.8.2 The 'font-face' element
The 'font-face' element
is an XML structure which
corresponds directly to the
@font-face facility in CSS2. It can be used to describe the
characteristics of any font, SVG font or otherwise.
When used to describe the characteristics of an SVG font
contained within the same document, it is recommended that the
'font-face' element be a
child of the 'font' element it is describing
so that the 'font' element can be
self-contained and fully-described. In this case, any 'font-face-src' elements within
the 'font-face' element are
ignored as it is assumed that the 'font-face' element is describing
the characteristics of its parent 'font' element.
Attribute definitions:
- font-family = "<string>"
Same syntax and semantics as the
'font-family' descriptor
within an
@font-face rule.
Animatable:
no.
- font-style = "all | [ normal | italic | oblique] [,
[normal | italic | oblique]]*"
Same syntax and semantics as the
'font-style' descriptor
within an
@font-face rule. The style of a font. Takes on the same
values as the 'font-style'
property, except that a comma-separated list is
permitted.
The lacuna value
is 'all'.
Animatable:
no.
- font-weight = "all | [normal | bold |100 | 200 | 300 |
400 | 500 | 600 | 700 | 800 | 900] [, [normal | bold |100 |
200 | 300 | 400 | 500 | 600 | 700 | 800 |
900]]*"
-
Same syntax and semantics as the
'font-weight'
descriptor within an
@font-face rule.
The weight of a face relative to others in the same font
family. Takes on the same values as the 'font-weight'
property with three exceptions:
- relative keywords (bolder, lighter) must not be used
- a comma-separated list of values may be used, for
fonts that contain multiple weights
- an additional keyword, 'all', may be used. 'all'
indicates that the font will match for all possible
weights; either because it contains multiple weights,
or because that face only has a single weight.
The lacuna value
is 'all'.
Animatable: no.
- unicode-range = "<urange> [,
<urange>]*"
Same syntax and semantics as the
'unicode-range'
descriptor within an
@font-face rule. The range of ISO 10646 characters [UNICODE]
possibly covered by the glyphs in the font. Except for any
additional information provided in this specification, the
normative definition of the attribute is in [CSS2].
The lacuna value
is 'U+0-10FFFF'.
Animatable:
no.
- units-per-em = "<number>"
Same syntax and semantics as the
'units-per-em'
descriptor within an
@font-face rule. The number of coordinate units on the
em square, the size of the design grid on which glyphs are
laid out.
This value should be specified as nearly every
other attribute requires the definition of a design
grid.
The lacuna value
is '1000'.
Animatable:
no.
- panose-1 = "[<integer>]{10}"
Same syntax and semantics as the
'panose-1' descriptor
within an
@font-face rule. The Panose-1 number, consisting of ten
decimal integers, separated by white space. Except for any
additional information provided in this specification, the
normative definition of the attribute is in [CSS2].
The lacuna value
is '0 0 0 0 0 0 0 0 0 0'.
Animatable:
no.
- stemv = "<number>"
Same syntax and semantics as the
'stemv' descriptor
within an
@font-face rule.
Animatable:
no.
- stemh = "<number>"
Same syntax and semantics as the
'stemh' descriptor
within an
@font-face rule.
Animatable:
no.
- slope = "<number>"
Same syntax and semantics as the
'slope' descriptor
within an
@font-face rule. The vertical stroke angle of the font.
Except for any additional information provided in this
specification, the normative definition of the attribute is
in [CSS2].
The lacuna value
is '0'.
Animatable:
no.
- cap-height = "<number>"
Same syntax and semantics as the
'cap-height' descriptor
within an
@font-face rule. The height of uppercase glyphs in the
font within the font coordinate system.
Animatable:
no.
- x-height = "<number>"
Same syntax and semantics as the
'x-height' descriptor
within an
@font-face rule. The height of lowercase glyphs in the
font within the font coordinate system.
Animatable:
no.
- accent-height = "<number>"
The distance from the origin to the top of accent
characters, measured by a distance within the font
coordinate system.
If the attribute is not specified, the effect is as if the
attribute were set to the value of the 'ascent' attribute. If this
attribute is used, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
- ascent = "<number>"
Same syntax and semantics as the
'ascent' descriptor
within an
@font-face rule. The maximum unaccented height of the
font within the font coordinate system.
If the attribute is not specified, the effect is as if the
attribute were set to the difference between the 'units-per-em' value and the 'vert-origin-y' value for the
corresponding font.
Animatable:
no.
- descent = "<number>"
Same syntax and semantics as the
'descent' descriptor
within an
@font-face rule. The maximum unaccented depth of the
font within the font coordinate system.
If the attribute is not specified, the effect is as if the
attribute were set to the 'vert-origin-y' value for the
corresponding font.
Animatable:
no.
- widths = "<string>"
Same syntax and semantics as the
'widths' descriptor
within an
@font-face rule.
Animatable:
no.
- bbox = "<string>"
Same syntax and semantics as the
'bbox' descriptor within
an
@font-face rule.
Animatable:
no.
- ideographic = "<number>"
For horizontally oriented glyph layouts, indicates the
alignment coordinate for glyphs to achieve ideographic
baseline alignment. The value is an offset in the font
coordinate system. If this attribute is provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
- alphabetic = "<number>"
Same syntax and semantics as the
'baseline' descriptor
within an
@font-face rule. For horizontally oriented glyph
layouts, indicates the alignment coordinate for glyphs to
achieve alphabetic baseline alignment. The value is an
offset in the font coordinate system. If this attribute is
provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
- mathematical = "<number>"
Same syntax and semantics as the
'mathline' descriptor
within an
@font-face rule. For horizontally oriented glyph
layouts, indicates the alignment coordinate for glyphs to
achieve mathematical baseline alignment. The value is an
offset in the font coordinate system. If this attribute is
provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
- hanging = "<number>"
For horizontally oriented glyph layouts, indicates the
alignment coordinate for glyphs to achieve hanging baseline
alignment. The value is an offset in the font coordinate
system. If this attribute is provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
- underline-position = "<number>"
The ideal position of an underline within the font
coordinate system. If this attribute is provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
-
underline-thickness = "<number>"
The ideal thickness of an underline, expressed as a
length within the font coordinate system. If this attribute
is provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
-
strikethrough-position = "<number>"
The ideal position of a strike-through within the font
coordinate system. If this attribute is provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
-
strikethrough-thickness = "<number>"
The ideal thickness of a strike-through, expressed as a
length within the font coordinate system. If this attribute
is provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
- overline-position = "<number>"
The ideal position of an overline within the font
coordinate system. If this attribute is provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
- overline-thickness = "<number>"
The ideal thickness of an overline, expressed as a
length within the font coordinate system. If this attribute
is provided, the 'units-per-em' attribute must
also be specified.
Animatable:
no.
17.8.3 The 'font-face-src' element
The 'font-face-src' element, together with the 'font-face-uri' elements described further down correspond to the 'src' descriptor within an
@font-face rule. (Refer to the descriptions of the
@font-face rule
and 'src' descriptor
in the CSS 2 specification ([CSS2], sections 15.3.1 and 15.3.5).
A 'font-face-src' element contains a
'font-face-uri' element. The 'font-face-src' element is used for referencing fonts defined elsewhere.
17.8.4 The 'font-face-uri' element
The 'font-face-uri' element
is used within a 'font-face-src' element to reference a font defined inside or outside of the current SVG document.
When a 'font-face-uri' is referencing
an SVG font, then
that reference must be to an SVG 'font' element, therefore
requiring the use of a fragment identifier (see [IRI]). The
referenced 'font' element can be local
(i.e., within the same document as the 'font-face-uri' element) or
remote (i.e., within a different document).
Example font03 references an external SVG font,
which was defined in example font01.svg.
<?xml version="1.0" encoding="UTF-8"?>
<svg version="1.2" baseProfile="tiny" viewBox="0 0 110 70" xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Font example</title>
<defs>
<font-face font-family="larabie-anglepoise">
<font-face-src>
<font-face-uri xlink:href="font01.svg#la"/>
</font-face-src>
</font-face>
</defs>
<rect x="00" y="00" width="110" height="70" stroke="#777" fill="none"/>
<text x="10" y="50" font-family="larabie-anglepoise" font-size="70" fill="#FDD" stroke="#533"
stroke-width="1.6">SVG</text>
</svg>
