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<concept id="GUID-5042997F-4B8C-538D-B1E0-DD82F5283BB6" xml:lang="en"><title>Linked

Fonts Guide</title><shortdesc>The linked font feature allows the creation of linked typefaces

using characters from two or more existing typefaces. Once created, linked

typefaces are available to all users. Application developers do not need to

know whether a font is a linked font or a real font. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p> </p>

<p> <b>Target audience</b>: Device creators. </p>

<section><title>Key concepts and terms</title> <p>See <xref href="GUID-90644B52-69D7-595C-95E3-D6F7A30C060D.dita">Font

and Text Services Collection Overview</xref>. </p> </section>

<section><title>Overview</title> <p>A linked typeface can be considered a

virtual typeface that has a name and consists of one or more typefaces (open

fonts only). A typeface is usually made up of an alphabet of letters, numerals

and punctuation marks. It may include or consist entirely of ideograms and

symbols. </p> <p>The following diagram represents a linked typeface that consists

of characters from Chinese and English typefaces. </p> <fig id="GUID-D9F370EF-BA91-5D8B-B963-D3B6EBEFAFF5">

<title>              Figure 1: An example linked typeface that contains Chinese

and              English characters            </title>

<image href="GUID-ACC2777E-F555-58ED-82D0-6F8423FB3EA3_d0e660750_href.png" placement="inline"/>

</fig> <p>Once a linked typeface has been successfully created, fonts can

be derived from it and rasterized in just the same way as from a non-linked

typeface. Similarly clients request a font from a linked typeface in the same

way as from any other typeface. </p> <p>Using linked typefaces reduces the

ROM size because it reduces the number of font files that are required. The

following table provides an example that demonstrates this. </p> <table id="GUID-CB3CE0D8-7E18-56D5-AC1C-D4E765410198">

<tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

<thead>

<row>

<entry>Using standard unlinked fonts</entry>

<entry>Using linked fonts</entry>

</row>

</thead>

<tbody>

<row>

<entry><p>Chinese and Bold English </p> </entry>

<entry><p>Chinese </p> </entry>

</row>

<row>

<entry><p>Chinese and Italic English </p> </entry>

<entry><p>English </p> </entry>

</row>

<row>

<entry><p>Chinese and Bold Italic English </p> </entry>

<entry><p>Linked Font File </p> </entry>

</row>

<row>

<entry><p>Chinese and Underline English </p> </entry>

<entry/>

</row>

</tbody>

</tgroup>

</table> <p>A linked typeface can contain more than one complex font (for

example, another linked font). The font rasterizer merges the tables required

for the shaping engine. </p> <p><b>The Canonical font </b> </p> <p>The creator

of a linked typeface must specify one of the component typefaces as the principal,

or canonical, typeface. If no font is specified as the canonical font, an

error is returned at registration. Similarly an error is returned if more

than one font is specified as the canonical font. </p> <p>When a character

or character metric is requested from a linked font, the real fonts that make

it up are checked, one after another, in the order in which they were originally

added to the linked typeface, until a match is found and the

requested information can be returned. If no match is found in any of the

real fonts within a linked font, the missing character glyph is supplied from

the canonical font. </p> <p><b>Typeface groups </b> </p> <p>A linked typeface

must be created with at least one typeface group and each typeface must belong

to a typeface group. A typeface group defines metrics applicable to all of

the typefaces that it contains. The metrics are as follows: </p> <ul>

<li id="GUID-B6AA0A72-EE60-5BC1-9BC4-488ECB417D02"><p>Scaling Option: The

different ways in which a typeface can be scaled. (None, up, down, or both

up and down.) </p> </li>

<li id="GUID-59A4FDD5-5052-5BE8-8C29-B169E857B669"><p>Baseline Shift: Whether

the font baseline can be shifted or not. </p> </li>

<li id="GUID-65082783-3EAF-5C8E-ACA8-E9D264DD2EE4"><p>Boldness Percentage:

How bold a bold font is. </p> </li>

<li id="GUID-1BE6F5B0-71D8-5B1F-B087-037DEA0B499B"><p>Italic Angle: The angle

(in percent) of italic text. </p> </li>

</ul> </section>

<section><title>Linked typeface creation</title> <p>You create a linked typeface

in two stages, as shown in the following diagram. First you build up the specification.

Then when the specification is complete, you register it with the <xref href="GUID-71DADA82-3ABC-52D2-8360-33FAEB2E5DE9.dita">Font

and Bitmap Server</xref>. </p> <fig id="GUID-2AC8C198-0BDB-5D69-B53D-3391F33658E7">

<title>              Figure 2: The linked typeface creation process      

     </title>

<image href="GUID-192003B7-631D-5AF6-9511-119EF5853054_d0e660894_href.png" placement="inline"/>

</fig> <p>The following diagram represents the structure of the specification

for the Chinese - English example shown in Figure 1 above. </p> <fig id="GUID-F44F3735-B486-5870-9514-10B80ADDDE99">

<title>              Figure 3: The structure of the specification for the

Chinese -              English example.            </title>

<image href="GUID-597D496F-D85A-5FFD-B9CA-FDCA3E016BE7_d0e660905_href.png" placement="inline"/>

</fig> <p>See <xref href="GUID-5B4D38A7-DCDC-51D8-A349-050CF0FD1586.dita">Creating

a Linked Typeface</xref> for more information. </p> </section>

<section><title>Related APIs</title> <p>The following table shows the linked

typeface classes. They are primarily designed for the creation of device system

fonts. The platform security capability <codeph>ECapabilityWriteDeviceData</codeph> is

required to register linked typefaces. <codeph>ECapabilityReadDeviceData</codeph> is

required to fetch linked typeface information from the <xref href="GUID-71DADA82-3ABC-52D2-8360-33FAEB2E5DE9.dita">Font

and Bitmap Server</xref>. </p> <table id="GUID-4485D14A-2A96-5D1D-BDF6-56E91EE4F7A2">

<tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

<thead>

<row>

<entry>Class</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><p> <xref href="GUID-6BE49D00-7174-3FEC-A944-FE4A5228C13E.dita"><apiname>CLinkedTypefaceSpecification</apiname></xref>  </p> </entry>

<entry><p>The specification of a linked typeface, made up of groups and typefaces. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-DDFD0FCB-8413-3FF2-A8D7-A052C30592C9.dita"><apiname>CLinkedTypefaceElementSpec</apiname></xref>  </p> </entry>

<entry><p>Specifies an individual typeface within a linked typeface. </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-623C40B5-A8FB-3FEE-9F92-254CAB580C5B.dita"><apiname>CLinkedTypefaceGroup</apiname></xref>  </p> </entry>

<entry><p>Represents the typeface group. Groups have attributes that control

how the rasterizer draws the typefaces within the group. </p> </entry>

</row>

</tbody>

</tgroup>

</table> </section>

</conbody><related-links>

<link href="GUID-5B4D38A7-DCDC-51D8-A349-050CF0FD1586.dita"><linktext>Creating

a Linked Typeface</linktext></link>

<link href="GUID-90644B52-69D7-595C-95E3-D6F7A30C060D.dita"><linktext>Font and

Text Services Collection Overview </linktext></link>

<link href="GUID-416A3756-B5D5-5BCD-830E-2371C5F6B502.dita"><linktext>Font Store

Component Overview </linktext></link>

<link href="GUID-71DADA82-3ABC-52D2-8360-33FAEB2E5DE9.dita"><linktext> Font and

Bitmap Server Component Overview</linktext></link>