10 Text

Contents

• 10.1 Introduction
• 10.2 Characters and their corresponding glyphs
• 10.3 The 'text' element
• 10.4 The 'tspan' element
• 10.5 The 'tref' element
• 10.6 Text layout
  • 10.6.1 Text layout introduction
  • 10.6.2 Setting the primary text advance direction
  • 10.6.3 Glyph orientation with a text run
  • 10.6.4 Relationship with bi-directionality
• 10.7 Text alignment properties
• 10.8 Font selection properties
• 10.9 Spacing properties
• 10.10 Text decoration
• 10.11 Text on a path
  • 10.11.1 Introduction to text on a path
  • 10.11.2 The 'textPath' element
  • 10.11.3 Text on a path layout rules
• 10.12 Alternate glyphs
• 10.13 White space handling
• 10.14 Text selection
• 10.15 DOM interfaces
  • 10.15.1 Interface SVGTextContentElement
  • 10.15.2 Interface SVGTextElement
  • 10.15.3 Interface SVGTextPositioningElement
  • 10.15.4 Interface SVGTSpanElement
  • 10.15.5 Interface SVGTRefElement
  • 10.15.6 Interface SVGTextpathElement
  • 10.15.7 Interface SVGAltGlyphElement
  • 10.15.8 Interface SVGAltGlyphDefElement
  • 10.15.9 Interface SVGSVGGlyphSubElement

10.1 Introduction

Text that is to be rendered as part of an SVG document fragment is specified using the 'text' element. The characters to be drawn are expressed as XML character data [XML10] inside the 'text' element.

SVG's 'text' elements are rendered like other graphics elements. Thus, coordinate system transformations, painting, clipping and masking features apply to 'text' elements in the same way as they apply to shapes such as paths and rectangles.

Each 'text' element causes a single string of text to be rendered. SVG performs no automatic line breaking or word wrapping. To achieve the effect of multiple lines of text:

• The author or authoring package needs to pre-compute the line breaks and use multiple 'text' elements (one for each line of text).
• The author or authoring package needs to pre-compute the line breaks and use a single 'text' element with one or more 'tspan' child elements with appropriate values for attributes x, y, dx and dy to set new start positions for those characters which start new lines. (This approach allows user text selection across multiple lines of text -- see Text selection and clipboard operations.)
• Express the text to be rendered in another XML namespace such as XHTML [XHTML10] embedded inline within a 'foreignObject' element. (Note: the exact semantics of this approach are not completely defined at this time.)

The text strings within 'text' elements can be rendered in a straight line or rendered along the outline of a 'path' element. SVG supports the following international text processing features for both straight line text and text on a path:

• horizontal and vertical orientation of text
• left-to-right, right-to-left and bi-directional text (e.g., for mixing Roman scripts with Arabic or Hebrew scripts)
• when SVG fonts are used, automatic selection of the correct glyph corresponding to the current form for Arabic and Han text

Because SVG text is packaged as XML character data [XML10]:

• Text data in SVG content is readily accessible to the visually impaired (see Accessibility Support)
• In many viewing scenarios, the user will be able to search for and select text strings and copy selected text strings to the system clipboard (see Text selection)
• XML-compatible web search engines will find text strings in SVG content with no additional effort over what they need to do to find text strings in other XML documents

Multi-language SVG content is possible by substituting different text strings based on the user's preferred language.

For accessibility reasons, it is recommended that text which is included in a document have appropriate semantic markup to indicate its function. See SVG accessibility guidelines for more information.
 

10.2 Characters and their corresponding glyphs

In XML [XML10], textual content is defined in terms of XML characters, where each character is defined by a particular character (i.e., code point) in Unicode [UNICODE]. Fonts, on the other hand, consists of a collection of glyphs, where each glyph consists of some sort of identifier (in some cases a string, in other cases a number) along with drawing instructions for rendering that particular glyph.

In many cases, there is a one-to-one mapping of Unicode characters (i.e., Unicode code points) to glyphs in a font. For example, it is common for a Roman font to contain a single glyph for each of the standard ASCII characters (i.e., A-to-Z, a-to-z, 0-to-9, plus the various punctuation characters found in ASCII). Thus, in most situations, the string "XML", which consists of three Unicode characters, would be rendered by the three glyphs corresponding to "X", "M" and "L", respectively.

In various other cases, however, there is not a strict one-to-one mapping of Unicode characters to glyphs. Some of the circumstances when the mapping is not one-to-one:

• Ligatures - For best looking typesetting, it is often desirable that particular sequences of characters are rendered as a single glyph. An example is the word "office". Many fonts will define an "ffi" ligature. When the word "office" is rendered, sometimes the user agent will render the glyph for the "ffi" ligature instead of rendering distinct glyphs (i.e., "f", "f" and "i") for each of the three characters. Thus, for ligatures, multiple Unicode characters map to a single glyph.
• Composite characters - In various situations, commonly used adornments such as diacritical marks will be stored once in a font as a particular glyph and then composed with one or more other glyphs to result in the desired character. For example, it is possible that a font engine might render the é character by first rendering the glyph for e and then rendering the glyph for ´ (the accent mark) such that the accent mark will appear over the e. In this situation, a single Unicode character map to multiple glyphs.
• Glyph substitution - Some typography systems examine the nature of the textual content and utilize different glyphs in different circumstances. For example, in Arabic, the same Unicode character might render as any of four different glyphs, depending on such factors as whether the character appears at the start, the end or the middle of a text string. In these situations, a single Unicode character might map to one of several alternative glyphs.
• Alternative glyph specification - SVG contains a facility for the author to explicitly specify that a particular sequence of Unicode characters is to be rendered using a particular glyph. (See Alternate glyphs.) When this facility is used, multiple Unicode characters map to a single glyph.

In many situations, the algorithms for mapping from characters to glyphs are system-dependent, resulting in the possibility that the rendering of text might be (usually slightly) different when viewed in different user environments. If the author of SVG content requires precise selection of fonts and glyphs, then the recommendation is that the necessary fonts (potentially subsetted to only include only the glyphs needed for the given document) be available either as SVG fonts embedded within the SVG content or as web fonts posted at the same web location as the SVG content.

10.3 The 'text' element

The 'text' element defines a graphics element consisting of text. The XML [XML10] character data within the 'text' element, along with relevant attributes and properties and character-to-glyph mapping tables within the font itself, define the glyphs to be rendered. (See Characters and their corresponding glyphs.) The attributes and properties on the 'text' element indicate such things as the writing direction, font specification and painting attributes which describe how exactly to render the characters. Subsequent sections of this chapter describe the relevant text-specific attributes and properties.

Since 'text' elements are rendered using the same rendering methods as other graphics element, all of the same coordinate system transformations, painting, clipping and masking features that apply to shapes such as paths and rectangles also apply to 'text' elements.

The 'text' renders its first character at the initial current text position, which is established by the x and y attributes. After the glyph(s) corresponding to the given character is(are) rendered, the current text position is updated for the next character. In the simplest case, the new current text position is the previous current text position plus the glyphs' text advance value (horizontal or vertical). See text layout for a description of glyph placement and glyph advance.

<!ENTITY % textExt "" >
<!ELEMENT text (#PCDATA|tspan|tref|textPath|altglyph|use|animate|set|animateMotion|animateColor|animateTransform
                %geExt;%textExt;)* >
<!ATTLIST text
  id ID #IMPLIED
  xml:lang NMTOKEN #IMPLIED
  xml:space (default|preserve) #IMPLIED
  class NMTOKENS #IMPLIED
  style CDATA #IMPLIED
  transform CDATA #IMPLIED
  %graphicsElementEvents;
  system-required NMTOKEN #IMPLIED
  system-language CDATA #IMPLIED
  x CDATA #IMPLIED
  y CDATA #IMPLIED >

Example text01 below expresses all values in physical units such as centimeters and points. The 'text' element contains the text string "Hello, out there" which will be rendered onto the canvas using the Verdana font family with font size of 12 points with the glyphs filled with the color blue.

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm">
  <desc>Example text01 - 'Hello, out there' in blue</desc>

  <text x="2.5cm" y="1.5cm" 
        style="font-family:Verdana; font-size:16pt; fill:blue">
    Hello, out there
  </text>
</svg>

Example text01

View this example as SVG (SVG-enabled browsers only)
 

Example text02 below expresses the x and y attributes and the 'font-size' property in the user coordinate system set up by the viewBox attribute on the 'svg' element. The 'text' element contains the text string "Text in user space."

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm" viewBox="0 0 1000 300">
  <desc>Example text02 - Text in user space</desc>

  <text x="250" y="150" 
        style="font-family:Verdana; font-size:42.333; fill:blue">
    Text in user space
  </text>
</svg>

Example text02

View this example as SVG (SVG-enabled browsers only)
 

10.4 The 'tspan' element

Within a 'text' element, text and font properties and the current text position can be adjusted with absolute or relative coordinate values by including a 'tspan' element.

<!ENTITY % tspanExt "" >
<!ELEMENT tspan (#PCDATA|tspan|tref|altglyph|animate|set|animateColor
                %tspanExt;)* >
<!ATTLIST tspan
  id ID #IMPLIED
  xml:lang NMTOKEN #IMPLIED
  xml:space (default|preserve) #IMPLIED
  class NMTOKENS #IMPLIED
  style CDATA #IMPLIED
  %graphicsElementEvents;
  system-required NMTOKEN #IMPLIED
  system-language CDATA #IMPLIED
  x CDATA #IMPLIED
  y CDATA #IMPLIED
  dx CDATA #IMPLIED
  dy CDATA #IMPLIED
  rotate CDATA #IMPLIED >

The x, y, dx, dy and rotate on the 'tspan' element are useful in high-end typography scenarios where individual glyphs requires exact placement. These attributes are useful for minor positioning adjustments between characters or for major positioning adjustments, such as moving the current text position to a new location to achieve the visual effect of a new line of text. Multi-line 'text' elements are possible by defining different 'tspan' elements for each line of text, with attributes x, y, dx and/or dy defining the position of each 'tspan'. (An advantage of such an approach is that users will be able to perform multi-line text selection.)

In situations where advanced typographic control is required and micro-level positioning adjustment are necessary, the SVG content designer needs to ensure that the necessary font will be available for all viewers of the document (e.g., package up the necessary font data in the form of an SVG font or an alternative web font format which is stored at the same web site as the SVG content) and that the viewing software will process the font in the expected way (the capabilities, characteristics and font layout mechanisms vary greatly from system to system). If the SVG content contains x, y, dx or dy attribute values which are meant to correspond to a particular font processed by a particular set of viewing software and either of these requirements is not met, then the text might display with poor quality.

The following additional rules apply to attributes x, y, dx, dy, rotate when they contain a list of numbers:

• Required behavior when multiple XML characters map to a single glyph (e.g., when a ligature is used) - Assume that the i-th and (i+1)-th XML characters map to a single glyph. In this case, the i-th value for the x, y, dx, dy and rotate attributes all apply when rendering the glyph. For the (i+1)-th values, however, the x, y and rotate value are not applied (although the final rotate value would still apply to subsequent characters), whereas the dx and dy are applied to the subsequent XML character (i.e., the (i+2)-th character), if one exists.
• Relationship to right-to-left text and bi-directionality - Text is laid out in a two-step process, where any right-to-left and bi-directional text is first re-ordered into a left-to-right string, and then text layout occurs with the re-ordered text string. Whenever the character data within a 'tspan' element is re-ordered, the corresponding elements within the x, y, dx, dy and rotate are also re-ordered to maintain the correspondence. For example, suppose that you have the following 'tspan' element:

  <tspan dx="11 12 13 14 15 0 21 22 23 0 31 32 33 34 35 36">Roman and Arabic</span>

  and that the word "Arabic" will be drawn right-to-left. First, the character data and the corresponding values in the dx list will be reordered, such that the text string will be "Roman and cibarA" and the list of values for the dx attribute will be "11 12 13 14 15 0 21 22 23 0 36 35 34 33 32 31". After this re-ordering, the characters will be positioned using standard left-to-right layout rules.
• Nested 'tspan' elements - The x, y, dx, dy and rotate attributes on a given 'tspan' element apply only to the character data that is directly within that 'tspan' element and do not apply to the character data within child (i.e., nested) 'tspan' elements. If the child/nested 'tspan' elements require positioning adjustments or rotation values, the child/nested 'tspan' elements need to specify x, y, dx, dy and rotate values for their own character data.

The following examples show basic use of the 'tspan' element.

Example tspan01 uses a 'tspan' element to indicate that the word "not" is to use a bold font and have red fill.

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm">
  <desc>Example tspan01 - using tspan to change visual attributes</desc>

  <g style="font-family:Verdana; font-size:12pt">
    <text x="2cm" y="1.5cm" style="fill:blue">
      You are
        <tspan style="font-weight:bold; fill:red">not</tspan>
      a banana.
    </text>
  </g>
</svg>

Example tspan01

View this example as SVG (SVG-enabled browsers only)
 

Example tspan02 uses the dx and dy attributes on the 'tspan' to adjust the current text position horizontally and vertically for particular text strings within a 'text' element.

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm">
  <desc>Example tspan02 - using tspan's dx and dy attributes 
        for incremental positioning adjustments</desc>

  <g style="font-family:Verdana; font-size:12pt">
    <text x="2cm" y="1.5cm" style="fill:blue">
      But you
        <tspan dx="2em" dy="-.5cm" style="font-weight:bold; fill:red">
          are
        </tspan>
        <tspan dy="1cm">
           a peach!
        </tspan>
    </text>
  </g>
</svg>

Example tspan02

View this example as SVG (SVG-enabled browsers only)
 

Example tspan03 uses the x and y attributes on the 'tspan' to establish a new absolute current text position for each glyph to be rendered. The example shows two lines of text within a single 'text' element. Because both lines of text are within the same 'text' element, the user will be able to select through both lines of text and copy the text to the system clipboard in user agents that support text selection and clipboard operations,

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm">
  <desc>Example tspan03 - using tspan's x and y attributes 
        for multiline text and precise glyph positioning</desc>

  <g style="font-family:Verdana; font-size:12pt">
    <text style="fill:rgb(255,164,0)">
      <tspan x="3.0cm 3.5cm 4.0cm 4.5cm 5.5cm 6.0cm 6.5cm" y="1cm">
        Cute and
      </tspan>
      <tspan x="3.75cm 4.25cm 4.75cm 5.25cm 5.75cm" y="2cm">
         fuzzy
      </tspan>
    </text>
  </g>
</svg>

Example tspan03

View this example as SVG (SVG-enabled browsers only)
 

10.5 The 'tref' element

The textual content for a 'text' can be either character data directly embedded within the 'text' element or the character data content of a referenced element, where the referencing is specified with a 'tref' element.

<!ENTITY % trefExt "" >
<!ELEMENT tref (animate|set|animateColor
                %trefExt;)* >
<!ATTLIST tref
  id ID #IMPLIED
  xml:lang NMTOKEN #IMPLIED
  xml:space (default|preserve) #IMPLIED
  class NMTOKENS #IMPLIED
  style CDATA #IMPLIED
  %graphicsElementEvents;
  system-required NMTOKEN #IMPLIED
  system-language CDATA #IMPLIED
  x CDATA #IMPLIED
  y CDATA #IMPLIED
  dx CDATA #IMPLIED
  dy CDATA #IMPLIED
  rotate CDATA #IMPLIED
  %xlinkRefAttrs;
  xlink:href CDATA #REQUIRED >

All character data within the referenced element, including character data enclosed within additional markup, will be rendered.

The x, y, dx, dy and rotate attributes have the same meanings as for the 'tspan' element. The attributes are applied as if the 'tref' element was replaced by a 'tspan' with the referenced character data (stripped of all supplemental markup) embedded within the hypothetical 'tspan' element.

Example tref01 shows how to use character data from a different element as the character data for a given 'tspan' element. The first 'text' element (with id="ReferencedText") will not draw because it is part of a 'defs' element. The second 'text' element draws the string "Inline character data". The third 'text' element draws the string "Reference character data" because it includes a 'tspan' element which is a reference to element "ReferencedText", and that element's character data is "Referenced character data".

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm">
  <defs>
    <text id="ReferencedText">
      Referenced character data
    </text>
  </defs>
  <desc>Example tref01 - inline vs reference text content</desc>

  <text x="1cm" y="1cm" style="font-size:12pt; fill:blue">
    Inline character data
  </text>
  <text x="1cm" y="2cm" style="font-size:12pt; fill:red">
    <tref xlink:href="#ReferencedText"/>
  </text>
</svg>

Example tref01

View this example as SVG (SVG-enabled browsers only)
 

10.6 Text layout

10.6.1 Text layout introduction

This section describes the text layout features supported by SVG, which includes support for various international writing directions, such as left-to-right (e.g., Roman scripts), right-to-left (e.g., Hebrew or Arabic), bi-directional (e.g., mixing Roman with Arabic) and vertical (e.g., Asian scripts). The descriptions in this section assume straight line text (i.e., text that is either strictly horizontal or vertical with respect to the current user coordinate system). Subsequent sections describe the supplemental layout rules for text on a path.

Because SVG does not provide for automatic line breaks or word wrapping, internationalized text layout is simpler in SVG than in languages such as XHTML [XHTML10].

In processing a given 'text' element, the SVG user agent keeps track of the current text position. The initial current text position is established by the x and y attributes on the 'text' element. The current text position is adjusted after each glyph to establish a new current text position at which the next glyph shall be rendered. The adjustment to the current text position is based on the current text advance direction, the glyph orientation relative to the text advance direction, the metrics of the glyph just rendered, kerning tables in the font and the current values of various attributes and properties, such as the spacing properties and any x, y, dx and dy attributes on 'tspan' elements.

For each glyph to be rendered, the SVG user agent determines an appropriate reference point on the glyph which will be placed exactly at the current text position. The reference point is determined based on character cell metrics in the glyph itself, the current text advance direction and the glyph orientation relative to the text advance direction For the most common uses of Roman text (i.e., 'writing-mode:lr', 'text-anchor:start', and 'glyph-anchor:baseline') the reference point in the glyph will be the intersection of left edge of the glyph character cell (or some other glyph-specific X axis coordinate indicating a left-side origin point) with the baseline of the glyph. For most cases with top-to-bottom vertical text layout, the reference point will be either a glyph-specific origin point for top-to-bottom vertical text or the intersection of the center of the glyph with its top line (see [CSS2] for a definition of top line).

The various text layout diagrams in this section use the following symbols:

- wide-cell glyph (e.g. Han) which is the n-th character in the text run
- narrow-cell glyph (e.g. Roman) which is the n-th glyph in the text run
- connected glyph (e.g. Hebrew or Arabic) which is the n-th glyph in the text run

The orientation which the above symbols assume in the diagrams corresponds to the orientation that the glyphs they represent are intended to assume when rendered in the user agent. Spacing between these characters in the diagrams is usually symbolic, unless intentionally changed to make a point.

10.6.2 Setting the primary text advance direction

The 'writing-mode' property specifies whether the primary text advance direction for a 'text' element shall be left-to-right, right-to-left, or top-to-bottom. The 'writing-mode' property applies only to 'text' elements; the property is ignored for 'tspan', 'tref' and 'textPath' sub-elements. (Note that even when the primary text advance direction if left-to-right or right-to-left, some or all of the content within a given 'text' element might advance in the opposite direction because of the Unicode [UNICODE] bi-directional algorithm or because of explicit text advance overrides due to properties 'direction' and 'unicode-bidi'. For more on bi-directional text, see Relationship with bi-directionality.)

lr-tb | lr

Sets the primary text advance direction to left-to-right, as is common in most Roman-based documents. For most characters, the current text position is advanced from left to right after each glyph is rendered. (When the character data includes characters which are subject to the Unicode bi-directional algorithm, the text advance rules are more complex. See Relationship with bi-directionality).

rl-tb | rl

Sets the primary text advance direction to right-to-left, as is common in Arabic or Hebrew scripts.

tb-rl | tb

Sets the primary text advance direction to top-to-bottom, as is common in Asian scripts. Though hardly as frequent as horizontal, this type of vertical layout also occurs in Latin based documents, particularly in table column or row labels. In most cases, the vertical baselines running through the middle of each glyph are aligned.

10.6.3 Glyph orientation with a text run

In some cases, it is required to alter the orientation of a sequence of characters relative to the primary text advance direction. The requirement is particularly applicable to vertical layouts of East Asian documents, where sometimes half-width Roman text is to be displayed horizontally and other times vertically.

Two properties control the glyph orientation relative to the primary text advance direction. 'glyph-orientation-vertical' controls glyph orientation when the primary text advance direction is vertical. 'glyph-orientation-horizontal' controls glyph orientation when the primary text advance direction is horizontal.

<angle>

The value of the angle is a <integer> restricted to the range of -360 to +360 in 90-degree increments.
A value of 0 indicates that all glyphs are oriented with the bottom of the glyphs toward the primary text advance direction, resulting in glyphs which are stacked vertically on top of each other. A value of 90 indicates a rotation of 90 degrees clockwise from the "0" orientation. Negative angle values are computed modulo 360; thus, a value of -90 is equivalent to a value of 270.

auto

The glyph orientation relative to the primary text advance direction is determined automatically based on the Unicode character number of the rendered glyph.

Full-width ideographic and full-width Roman glyphs (excluding ideographic punctuation) are oriented as if an <angle> of "0" had been specified (i.e., glyphs are oriented with the bottom of the glyphs toward the primary text advance direction, resulting in glyphs which are stacked vertically on top of each other).

Ideographic punctuation and other ideographic characters having alternate horizontal and vertical forms shall use the vertical form of the glyph.

Text which is not full-width will be set as if an <angle> of "90" had been specified; thus, half-width Roman text will be rotated 90 degree clockwise versus full-width ideographic and full-width Roman text.

Note that a value of auto will generally produce the expected results in common uses of mixing Japanese with European characters; however, the exact algorithms are based on complex interactions between many factors, including font design, and thus different algorithms might be employed in different processing environments. For precise control, specify explicit <angle> values.

The glyph orientation affects the amount that the current text position advances as each glyph is rendered. When the primary text advance direction is vertical and the 'glyph-orientation-vertical' results in an orientation angle that is a multiple of 180 degrees, then the current text position is incremented according to the vertical metrics of the glyph. Otherwise, if the 'glyph-orientation-vertical' results in an orientation angle that is not a multiple of 180 degrees, then the current text position is incremented according to the horizontal metrics of the glyph.

The diagrams below illustrate different uses of 'glyph-orientation-vertical'. The diagram on the left shows the result of the mixing of full-width ideographic characters with half-width Roman characters when 'glyph-orientation-vertical' for the Roman characters is either auto or 90. The diagram on the right show the result of mixing full-width ideographic characters with half-width Roman characters when Roman characters are specified to have a 'glyph-orientation-vertical' of 0.

<angle>

The value of the angle is a <integer> restricted to the range of -360 to +360 in 90-degree increments.
A value of 0 indicates that all glyphs are oriented with the right edge of the glyphs toward the primary text advance direction, resulting in glyphs which are positioned side by side. A value of 90 indicates an orientation of 90 degrees clockwise from the "0" orientation. Negative angle values are computed modulo 360; thus, a value of -90 is equivalent to a value of 270.

The glyph orientation affects the amount that the current text position advances as each glyph is rendered. When the primary text advance direction is horizontal and the 'glyph-orientation-horizontal' results in an orientation angle that is a multiple of 180 degrees, then the current text position is incremented according to the horizontal metrics of the glyph. Otherwise, if the 'glyph-orientation-vertical' results in an orientation angle that is not a multiple of 180 degrees, then the current text position is incremented according to the vertical metrics of the glyph.

10.6.4 Relationship with bi-directionality

The characters in certain scripts are written from right to left. In some documents, in particular those written with the Arabic or Hebrew script, and in some mixed-language contexts, text in a single line may appear with mixed directionality. This phenomenon is called bidirectionality, or "bidi" for short.

The Unicode standard ([UNICODE], section 3.11) defines a complex algorithm for determining the proper directionality of text. The algorithm consists of an implicit part based on character properties, as well as explicit controls for embeddings and overrides. The SVG user agent applies this bidirectional algorithm when determining the layout of characters within a 'text' element. The 'direction' and 'unicode-bidi' properties allow authors to override the inherent directionality of the content characters and thus explicitly control how the elements and attributes of a document language map to this algorithm. These two properties are only applicable when the primary text advance direction is horizontal.

Because the directionality of a text depends on the structure and semantics of the document language, in most cases these properties will be used only by designers of document type descriptions (DTDs) or authors of special documents.

A more complete discussion of bi-directionality can be found in the "Cascading Style Sheets (CSS) level 2" specification [CSS2].

The processing model for right-to-left or bi-directional horizontal text is as follows. The user agent processes the characters which are provided in lexical order and re-orders the characters after processing the Unicode bi-directional algorithm and properties 'direction' and 'unicode-bidi', resulting in a potentially re-ordered list of characters which are now in left-to-right rendering order. Simultaneous with re-ordering of the characters, the x, y, dx, dy and rotate attributes on the 'tspan' and 'tref' elements are also re-ordered to maintain the original correspondence between characters and attribute values. While kerning or ligature processing might be font-specific, the preferred model is that kerning and ligature processing occurs between combinations of characters or glyphs after the characters have been re-ordered. Similarly, text selection occurs on the re-ordered text (i.e., based on visual layout rather than lexical layout).

When included in a 'text' element whose primary text advance direction is vertical, Arabic text has a default orientation where the glyphs are rotated 90 degrees counter-clockwise from standard vertically-oriented glyphs, making the default orientation of the Arabic glyphs the same as for half-width Roman glyphs.

This property specifies the base writing direction of text and the direction of embeddings and overrides (see 'unicode=bidi') for the Unicode bidirectional algorithm. For the 'direction' property to have any effect, the 'unicode=bidi' property's value must be 'embed' or 'override'. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for the specification for this property.

The 'direction' property applies only to text whose glyph orientation has the right edge of the glyphs oriented in the same direction as the primary text advance direction, which includes the usual case of horizontally-oriented Roman or Arabic text and the case of half-width Roman or Arabic characters rotated 90 degrees clockwise relative to a top-to-bottom primary text advance direction.

Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for the specification for this property.

10.7 Text alignment properties

Each text element establishes an initial current text position. The following properties are used to align the contents of a 'text' element relative to the current text position.

This property, which applies only to 'text' elements and is ignored for elements 'tspan', 'tref' and 'textPath', describes how the characters within a 'text' element are aligned relative to the initial current text position for the 'text' element. Values have the following meanings:

start

The rendered characters are aligned such that the start of the text string is at the initial current text position. For standard Roman text, this is comparable to left alignment. For Asian text with a vertical primary text direction, this is comparable to top alignment.

middle

The rendered characters are al current text position. For standard Roman text, this is comparable to center alignment.

end

The rendered characters are aligned such that the end of the text string is at the initial current text position. For standard Roman text, this is comparable to right alignment.

This property, which only applies to glyphs rendered horizontally (i.e., bottom of the glyph is parallel to the primary text advance direction), describes the vertical alignment of glyphs relative to the current text position. Values have the following meanings:

text-top

Align the glyph vertically relative such that the top of the glyph is aligned with the current text position. (Refer to the discussion of text-top under SVG fonts and the "text-top" value for the 'vertical-align' property in [CSS2].)

topline

Align the glyph vertically such that the "topline" of the glyph is aligned with the current text position. (Refer to the discussion of topline under SVG fonts and the "topline" font descriptor described in [CSS2].)

hanging

Align the glyph vertically such that the "hanging" position of the glyph is aligned with the current text position. (Refer to the discussion of hanging under SVG fonts.)

mathline

Align the glyph vertically such that the "mathline" of the glyph is aligned with the current text position. (Refer to the discussion of mathline under SVG fonts and the "mathline" font descriptor described in [CSS2].)

centerline

Align the glyph vertically such that the "centerline" of the glyph is aligned with the current text position. (Refer to the discussion of centerline under SVG fonts and the "centerline" font descriptor described in [CSS2].)

baseline

Align the glyph vertically such that the "baseline" of the glyph is aligned with the current text position. (Refer to the discussion of baseline under SVG fonts and the "baseline" font descriptor described in [CSS2].)

ideographic

Align the glyph vertically such that the "ideographic" position of the glyph is aligned with the current text position. (Refer to the discussion of ideographic under SVG fonts.)

text-bottom

Align the glyph vertically relative such that the bottom of the glyph is aligned with the current text position. (Refer to the discussion of text-bottom under SVG fonts and the "text-bottom" value for the 'vertical-align' property in [CSS2].)

This property, which only applies to glyphs rendered horizontally (i.e., bottom of the glyph is parallel to the primary text advance direction), provides for vertical adjustment of the current text position. Property values are cumulative; thus, the 'baseline-shift' value for the current element is added to all of the 'baseline-shift' values for its ancestors up to its parent 'text' element. Values have the following meanings:

super

Shift the text upward to the appropriate position for superscripts.

sub

Shift the text downward to the appropriate position for subscripts.

<length>

Shift the text vertically by the given distance.

10.8 Font selection properties

SVG uses the following font specification properties from CSS2. Any SVG-specific notes about these properties are contained in the descriptions below.

This property which font family is to be used to render the text, specified as a prioritized list of font family names and/or generic family names. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

This property specifies whether the text is to be rendered using a normal, italic or oblique face. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

This property indicates whether the text is to be rendered using the normal glyphs for lowercase characters or using small-caps glyphs for lowercase characters. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

This property refers to the boldness or lightness of the glyphs used to render the text, relative to other fonts in the same font family. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

This property indicates the desired amount of condensing or expansion in the glyphs used to render the text. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

This property refers to the size of the font from baseline to baseline when multiple lines of text are set solid in a multiline layout environment. For SVG, if a <length> is provided without a unit identifier (e.g., an unqualified number such as 128), the SVG user agent processes the <length> as a height value in the current user coordinate system.

If a <length> is provided with one of the CSS unit identifiers (e.g., 12pt or 10%), then the SVG user agent converts the <length> into a corresponding value in the current user coordinate system by applying the processing rules for CSS units and percentages. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

This property allows authors to specify an aspect value for an element that will preserve the x-height of the first choice font in a substitute font. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

Shorthand property for setting 'font-style', 'font-variant', 'font-weight', 'font-size', 'line-height' and 'font-family'. The 'line-height' property has no visual effect in SVG. Conforming SVG Viewers are not required to support the various system font options (caption, icon, menu, message-box, small-caption and status-bar) and can use a system font or one of the generic fonts instead.

Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

10.9 Spacing properties

This property specifies spacing behavior between text characters. For SVG, if a <length> is provided without a unit identifier (e.g., an unqualified number such as 128), the SVG user agent processes the <length> as a width value in the current user coordinate system.

If a <length> is provided with one of the CSS unit identifiers (e.g., .25em or 1%), then the SVG user agent converts the <length> into a corresponding value in the current user coordinate system by applying the processing rules for CSS units and percentages. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

This property specifies spacing behavior between words. For SVG, if a <length> is provided without a unit identifier (e.g., an unqualified number such as 128), the SVG user agent processes the <length> as a width value in the current user coordinate system.

If a <length> is provided with one of the CSS unit identifiers (e.g., .25em or 1%), then the SVG user agent converts the <length> into a corresponding value in the current user coordinate system by applying the processing rules for CSS units and percentages. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

10.10 Text decoration

This property describes decorations that are added to the text of an element. Conforming SVG Viewers are not required to support the blink value. Refer to the "Cascading Style Sheets (CSS) level 2" specification [CSS2] for more information about this property.

10.11 Text on a path

10.11.1 Introduction to text on a path

In addition to text drawn in a straight line, SVG also includes the ability to place text along the shape of a 'path' element. To specify that a block of text is to be rendered along the shape of a 'path', include the given text within a 'textPath' element which includes an xlink:href attribute with a URI reference to a 'path' element.

10.11.2 The 'textPath' element

<!ENTITY % textPathExt "" >
<!ELEMENT textPath (#PCDATA|tspan|tref|altglyph|animate|set|animateColor
                %textPathExt;)* >
<!ATTLIST textPath
  id ID #IMPLIED
  xml:lang NMTOKEN #IMPLIED
  xml:space (default|preserve) #IMPLIED
  class NMTOKENS #IMPLIED
  style CDATA #IMPLIED
  %graphicsElementEvents;
  system-required NMTOKEN #IMPLIED
  system-language CDATA #IMPLIED
  startOffset CDATA "0"
  %xlinkRefAttrs;
  xlink:href CDATA #REQUIRED >

Example toap01 provides a simple example of text on a path:

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm" viewBox="0 0 1000 300">
  <defs>
    <path id="MyPath"
          d="M 100 200 
             C 200 100 300   0 400 100
             C 500 200 600 300 700 200
             C 800 100 900 100 900 100" />
  </defs>
  <desc>Example toap01 - simple text on a path</desc>

  <use xlink:href="#MyPath" style="stroke:red" />
  <text style="font-family:Verdana; font-size:42.3333; fill:blue">
    <textPath xlink:href="#MyPath">
      We go up, then we go down, then up again
    </textPath>
  </text>
</svg>

Example toap01

View this example as SVG (SVG-enabled browsers only)
 

Example toap02 shows how 'tspan' elements can be included within 'textPath' elements to adjust styling attributes and adjust the current text position before rendering a particular glyph. The first occurrence of the word "up" is filled with the color red. Attribute dy is used to lift the word "up" from the baseline.

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm" viewBox="0 0 1000 300">
  <defs>
    <path id="MyPath"
          d="M 100 200 
             C 200 100 300   0 400 100
             C 500 200 600 300 700 200
             C 800 100 900 100 900 100" />
  </defs>
  <desc>Example toap02 - tspan within textPath</desc>

  <use xlink:href="#MyPath" style="fill:none; stroke:red" />
  <text style="font-family:Verdana; font-size:42.3333; fill:blue">
    <textPath xlink:href="#MyPath">
      We go 
      <tspan dy="30" style="fill:red">
        up
      </tspan>
      <tspan dy="-30">
        ,
      </tspan>
      then we go down, then up again
    </textPath>
  </text>
</svg>

Example toap02

View this example as SVG (SVG-enabled browsers only)
 

Example toap03 demonstrates the use of the startOffset attribute on the 'textPath' element to specify the start position of the text string as a particular position along the path. Notice that glyphs that fall off the end of the path are not rendered (see text on a path layout rules).

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm" viewBox="0 0 1000 300">
  <defs>
    <path id="MyPath"
          d="M 100 200 
             C 200 100 300   0 400 100
             C 500 200 600 300 700 200
             C 800 100 900 100 900 100" />
  </defs>
  <desc>Example toap03 - text on a path with startOffset attribute</desc>

  <use xlink:href="#MyPath" style="fill:none; stroke:red" />
  <text style="font-family:Verdana; font-size:42.3333; fill:blue">
    <textPath xlink:href="#MyPath" startOffset="80%">
      We go up, then we go down, then up again
    </textPath>
  </text>
</svg>

Example toap03

View this example as SVG (SVG-enabled browsers only)
 

10.11.3 Text on a path layout rules

Example toap04 will be used to illustrate the particular layout rules for text on a path that supplement the basic text layout rules for straight line horizontal or vertical text.

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG December 1999//EN" 
  "http://www.w3.org/Graphics/SVG/SVG-19991203.dtd">
<svg width="10cm" height="3cm" viewBox="0 0 1000 300">
  <defs>
    <path id="MyPath"
          d="M 100 100 
             C 150 100 250 200 300 200
             C 350 200 450 100 500 100
             C 550 100 650 200 700 200
             C 750 200 850 100 900 100" />
  </defs>
  <desc>Example toap04 = text on a path layout rules</desc>

  <use xlink:href="#MyPath" style="fill:none; stroke:red" />
  <text style="font-family:Verdana; font-size:63.5; fill:blue">
    <textPath xlink:href="#MyPath">
      Choose shame or get war 
    </textPath>
  </text>
</svg>

Example toap04

View this example as SVG (SVG-enabled browsers only)
 

The following picture does an initial zoom in on the first glyph in the 'text' element.

The small dot above shows the point at which the glyph is attached to the path. The box around the glyph shows the glyph is rotated such that its horizontal axis is parallel to the tangent of the curve at the point at which the glyph is attached to the path. The box also shows the glyph's charwidth (i.e., the amount which the current text position advances horizontally when the glyph is drawn using horizontal text layout).

The next picture zooms in further to demonstrate the detailed layout rules.

For horizontal text layout along a path, the layout rules are as follows:

• Determine the startpoint-on-the-path for the first glyph using attribute startOffset and, if present, the dx attribute on a 'tspan' element. (In the picture above, the startpoint-on-the-path is the leftmost dot on the path.)
• Determine the glyph's charwidth (i.e., the amount which the current text position advances horizontally when the glyph is drawn using horizontal text layout). (In the picture above, the charwidth is the distance between the two dots at the side of the box.)
• Determine the point on the curve which is charwidth distance along the path from the startpoint-on-the-path for this glyph, calculated using the user agent's distance along the path algorithm. This point is the endpoint-on-the-path for the glyph. (In the picture above, the endpoint-on-the-path for the glyph is the rightmost dot on the path.)
• Determine the midpoint-on-the-path, which is the point on the path which is "halfway" (user agents can choose either a distance calculation or a parametric calculation) between the startpoint-on-the-path and the endpoint-on-the-path. (In the picture above, the midpoint-on-the-path is shown as a white dot.)
• Determine the glyph-midline, which is the vertical line in the glyph's coordinate system that goes through the glyph's x-axis midpoint. (In the picture above, the glyph-midline is shown as a dashed line.)
• Position the glyph such that the glyph-midline passes through the midpoint-on-the-path and is perpendicular to the line through the startpoint-on-the-path and the endpoint-on-the-path.
• Align the glyph vertically relative to the midpoint-on-the-path based on property 'glyph-anchor' and any specified values for attribute dy on a 'tspan' element. In the example above, the 'glyph-anchor' property is unspecified, so the initial value of 'glyph-anchor:baseline' will be used. There are no 'tspan' elements; thus, the baseline of the glyph is aligned to the midpoint-on-the-path.
• For each subsequent glyph, set a new startpoint-on-the-path as the previous endpoint-on-the-path, but with appropriate adjustments taking into account kerning tables in the font and current values of various attributes and properties, including spacing properties and 'tspan' elements with values provided for attributes dx and dy. All adjustments are calculated as distance adjustments along the path, calculated using the user agent's distance along the path algorithm.
• Glyphs whose midpoint-on-the-path are off the end of the path are not rendered.
• Continue rendering glyphs until there are no more glyphs.

In the calculations above, if either the startpoint-on-the-path or the endpoint-on-the-path is off the end of the path, then extend the path beyond its end points with a straight line that is parallel to the tangent at the path at its end point so that the midpoint-on-the-path can still be calculated.

For 'tspan' elements that are children of 'textPath' elements, x and y attributes on 'tspan' elements have no effect on text layout.

Vertical, right-to-left and bi-directional text layout rules also apply to text on a path. Conceptually, the target path is stretched out into either a horizontal or vertical straight line segment. For horizontal text layout flows, the path is stretched out into a hypothetical horizontal line segment such that the start of the path is mapped to the left of the line segment. For vertical text layout flows, the path is stretched out into a hypothetical vertical line segment such that the start of the path is mapped to the top of the line segment. The standard text layout rules are applied to the hypothetical straight line segment and the result is mapped back onto the target path.

10.12 Alternate glyphs

There are situations such as ligatures, special-purpose fonts (e.g., a font for music symbols) or alternate glyphs for Asian text strings where it is required that a different glyph is used than the glyph which normally corresponds to the given character data. Also, The W3C Character Model [CHARMOD] encourages creators of XML to normalize character data to facilitate meaningful exchange of character data and to promote correct comparisons between character strings. This normalization potentially loses some information about which specific glyph is required to achieve a particular visual result.

The 'altGlyph' element provides control over the glyphs used to render particular character data.

<!ENTITY % altGlyphExt "" >
<!ELEMENT altGlyph (#PCDATA %altGlyphExt;)* >
<!ATTLIST altGlyph
  id ID #IMPLIED
  %xlinkRefAttrs;
  xlink:href CDATA #REQUIRED >

The 'altGlyphDef' element, which can only appear as a child of a 'defs' element, defines a list of possible glyph substitutions which can be referenced from an 'altGlyph' element. Each possible glyph substitution is defined by a 'glyphSub' child element. The first 'glyphSub' element which locates a substitute glyph will be applied.

<!ENTITY % altGlyphDefExt "" >
<!ELEMENT altGlyphDef (glyphSub %altGlyphDefExt;)* >
<!ATTLIST altglyphDef
  id ID #IMPLIED >

The 'glyphSub' element defines a possible glyph substitution, consisting of a font name, a glyph identifier and a font format.

<!ELEMENT glyphSub EMPTY >
<!ATTLIST glyphSub
  id ID #IMPLIED 
  font CDATA #REQUIRED
  glyphRef CDATA #REQUIRED
  format CDATA #REQUIRED >

10.13 White space handling

SVG supports the standard XML attribute xml:space to specify the handling of white space characters within a given 'text' element's character data. xml:space is an inheritable attribute which can have one of two values:

• default (the initial/default value for xml:space) - When xml:space="default", the SVG user agent will do the following. First, it will remove all carriage return and linefeed characters. Then it will convert all tab characters into space characters. Then, it will strip off all leading and trailing space characters. Then, all contiguous space characters will be consolidated.
• preserve - When xml:space="preserve", the SVG user agent will do the following. It will convert all carriage returns, linefeeds and tab characters into space characters. Then, it will draw all space characters, including leading, trailing and multiple contiguous space characters. Thus, when drawn with xml:space="preserve", the string "a   b" (three spaces between "a" and "b") will produce a larger separation between "a" and "b" than "a b" (one space between "a" and "b").

The following examples illustrate that line indentation can be important when using xml:space="default". The fragments below show two pairs of equivalent 'text' elements. Each pair consists of two equivalent 'text' elements, with the first 'text' element using xml:space='default' and the second using xml:space='preserve'. For these examples, there is no extra white space at the end of any of the lines (i.e., the line break occurs immediately after the last visible character).

[01]  <text xml:space='default'>
[02]    WS example
[03]    indented lines
[04]  </text>
[05]  <text xml:space='preserve'>WS example indented lines</text>
[06]
[07]  <text xml:space='default'>
[08]WS example
[09]non-indented lines
[10]  </text>
[11]  <text xml:space='preserve'>WS examplenon-indented lines</text>

The first pair of 'text' elements above show the effect of indented character data. The attribute xml:space='default' in the first 'text' element instructs the user agent to:

• convert all tabs (if any) to space characters,
• strip out all line breaks (i.e., strip out the line breaks at the end of lines [01], [02] and [03]),
• strip out all leading space characters (i.e., strip out space characters before "WS example" on line [02]),
• strip out all trailing space characters (i.e., strip out space characters before "</text>" on line [04]),
• consolidate all intermediate space characters (i.e., the space characters before "indented lines" on line [03]) into a single space character.

The second pair of 'text' elements above show the effect of indented character data. The attribute xml:space='default' in the third 'text' element instructs the user agent to:

• convert all tabs (if any) to space characters,
• strip out all line breaks (i.e., strip out the line breaks at the end of lines [07], [08] and [09]),
• strip out all leading space characters (there are no leading space characters in this example),
• strip out all trailing space characters (i.e., strip out space characters before "</text>" on line [10]),
• consolidate all intermediate space characters into a single space character (in this example, there are not intermediate space characters).

The xml:space attribute is:

    Animatable: no.

10.14 Text selection and clipboard operations

Conforming SVG viewers on systems which have the capacity for text selection (e.g., systems which are equipped with a pointer device such as a mouse) and which have system clipboards for copy/paste operations are required to support:

• user selection of text strings in SVG content
• the ability to copy selected text strings to the system clipboard

A text selection operation starts when all of the following occur:

• the user positions the pointing device over a glyph that has been rendered as part of a 'text' element, initiates a select operation (e.g., pressing the standard system mouse button for select operations) and then moves the pointing device while continuing the select operation (e.g., continuing to press the standard system mouse button for select operations)
• no other visible graphics element has been painted above the glyph at the point at which the pointing device was clicked
• no links or events have been assigned to the 'text' , 'tspan' or 'textPath' , element(s) (or their ancestors) associated with the given glyph.

As the text selection operation proceeds (e.g., the user continues to press the given mouse button), all associated events with other graphics elements are ignored (i.e., the text selection operation is modal) and the SVG user agent shall dynamically indicate which characters are selected by an appropriate highlighting technique, such as redrawing the selected glyphs with inverse colors. As the pointer is moved during the text selection process, the end glyph for the text selection operation is the glyph within the same 'text' element whose character cell is closest to the pointer. All characters within the 'text' element whose position within the 'text' element is between the start of selection and end of selection shall be highlighted, regardless of position on the canvas and regardless of any graphics elements that might be above the end of selection point.

Once the text selection operation ends (e.g., the user releases the given mouse button), the selected text will stay highlighted until an event occurs which cancels text selection, such as a pointer device activation event (e.g., pressing a mouse button).

Detailed rules for determining which characters to highlight during a text selection operation are provided in Text selection implementation notes.

For systems which have system clipboards, the SVG user agent is required to provide a user interface for initiating a copy of the currently selected text to the system clipboard. It is sufficient for the SVG user agent to post the selected text string in the system's appropriate clipboard format for plain text, but preferable if the SVG user agent also posts a rich text alternative which captures the various font properties associated with the given text string.

For bi-directional text, the user agent must support text selection in lexical order, which will result in discontinuous highlighting of glyphs due to the bi-directional reordering of characters. User agents can provide an alternative ability to select bi-directional text in visual rendering order (i.e., after bi-directional text layout algorithms have been applied), with the result that selected character data might be discontinous lexically. In this case, if the user requests that bi-directional text be copied to the clipboard, then the user agent is required to make appropriate adjustments to copy only the visually selected characters to the clipboard.

When feasible, it is recommended that generators of SVG attempt to order their text strings to facilitate properly ordered text selection within SVG viewing applications such as Web browsers.

10.15 DOM interfaces

10.15.1 Interface SVGTextContentElement

The SVGTextContentElement interface is inherited by various text-related interfaces, such as SVGTextElement, SVGTSpanElement, SVGTRefElement and SVGTextpathElement.

interface SVGTextContentElement : SVGStyledElement {

  long            getNumberOfChars();   // Number of characters in 'text' element
  float           getLength(); // From start of first char to end of last char
  float           getSubStringLength(in unsigned long charnum, in unsigned long nchars);
  SVGPoint        getStartPositionOfChar(in unsigned long charnum); // 0-based indexing???
  SVGPoint        getEndPositionOfChar(in unsigned long charnum); // 0-based indexing???
  SVGRect         getExtentOfChar(in unsigned long charnum); // 0-based indexing???
  float           getRotationOfChar(in unsigned long charnum); // 0-based indexing???
  long            getCharNumAtPosition(in SVGPoint); // Returns -1 is no char found
  void            selectSubString(in unsigned long charnum, in unsigned long nchars);
};

10.15.2 Interface SVGTextElement

The SVGTextElement interface corresponds to the 'text' element.

interface SVGTextElement : SVGTextContentElement {
  // SVGTransformedElement attributes
  readonly attribute  SVGElement       viewportElement; // element that established current viewport
           attribute  SVGTransformList transform;

  SVGRect      getBBox(); // tight bounding box on geometry of all contained 
                          // graphics elements, in userspace.
                          // Doesn't take into account stroke-width or filter effects, for example

  SVGMatrix    getNearestCTM(); // returns CTM (userspace to [nearest 'svg'] viewport transform matrix)
  SVGMatrix    getNearestCTMInverse()
               raises(SVGException); // returns inverse matrix (SVG_MATRIX_NOT_INVERTABLE)
  SVGMatrix    getFurthestCTM(); // returns CTM (userspace to [outermost 'svg'] viewport transform matrix)
  SVGMatrix    getFurthestCTMInverse()
               raises(SVGException); // returns inverse matrix (SVG_MATRIX_NOT_INVERTABLE)
  SVGMatrix    getScreenCTM(); // returns CTM (userspace to screen units transform matrix)
  SVGMatrix    getScreenCTMInverse()
               raises(SVGException); // returns inverse matrix (SVG_MATRIX_NOT_INVERTABLE)

  // Easy access to user units
  attribute SVGLength x;
  attribute SVGLength y;
};

10.15.3 Interface SVGTextPositioningElement

The SVGTextPositioningElement interface is inherited by text-related interfaces: SVGTSpanElement, SVGTRefElement and SVGTextpathElement.

interface SVGTextPositioningElement : SVGTextContentElement {
  attribute SVGLengthList x;
  attribute SVGLengthList y;
  attribute SVGLengthList dx;
  attribute SVGLengthList dy;
  attribute SVGLengthList rotate;
};

10.15.4 Interface SVGTSpanElement

The SVGTSpanElement interface corresponds to the 'tspan' element.

interface SVGTSpanElement : SVGTextPositioningElement {
};

10.15.5 Interface SVGTRefElement

The SVGTRefElement interface corresponds to the 'tref' element.

interface SVGTRefElement : SVGTextPositioningElement {
  attribute DOMString role;
  attribute DOMString title;
  attribute DOMString show;
  attribute DOMString actuate;
  attribute DOMString href;
};

10.15.6 Interface SVGTextpathElement

The SVGTextpathElement interface corresponds to the 'textPath' element.

interface SVGTextpathElement : SVGTextPositioningElement {
  attribute DOMString role;
  attribute DOMString title;
  attribute DOMString show;
  attribute DOMString actuate;
  attribute DOMString href;
  attribute SVGLength startOffset;
};

10.15.7 Interface SVGAltGlyphElement

The SVGAltGlyphElement interface corresponds to the 'altGlyph' element.

interface SVGAltGlyphElement : SVGTextContentElement {
  attribute DOMString role;
  attribute DOMString title;
  attribute DOMString show;
  attribute DOMString actuate;
  attribute DOMString href;
};

10.15.8 Interface SVGAltGlyphDefElement

The SVGAltGlyphDefElement interface corresponds to the 'altGlyphDef' element.

interface SVGAltGlyphDefElement : SVGElement {
};

10.15.9 Interface SVGSVGGlyphSubElement

The SVGSVGGlyphSubElement interface corresponds to the 'SVGGlyphSub' element.

interface SVGGlyphSub : SVGElement {
  attribute DOMString fontFamily;
  attribute DOMString glyphRef;
  attribute DOMString format;
};