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  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="GUID-EDAF2886-5296-53BD-B847-0E0D9B5FBF7E" xml:lang="en"><title>Special
requirements</title><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-FAEE5A94-6E06-4991-AA1C-ED8AAAF2CBA7"><title>Performance</title> <p>Since text objects are potentially
both large and complex, editing them can involve complex operations. It is
important on the one hand that text views have high performance, and on the
other that they require little memory, and have a usable API.</p> <p>Memory
use is minimised by the format band and by using only minimal format information
for purposes which require it — such as pagination, and print preview.</p> <p>One
key measure of perceived performance is responsiveness to user input. The
Text Views API support this by using background-priority active objects to
maintain the formatting of text in two contexts. Firstly, the formatting of
the format band is handled, where possible, using an active object which is
invisible to the user of the API. Secondly, pagination is handled, where required,
using an active object which is visibly part of the API.</p> </section>
<section id="GUID-5DEC7434-0626-468F-93DE-DCCCA760F8ED"><title>High-level GUI support</title> <p>For many purposes, such
as editing short text objects, a GUI-provided high-level editor provides a
convenient interface. </p> </section>
<section id="GUID-9855C622-5788-4873-A54B-306443CBBC1F"><title>Text content interfaces</title> <p>The <xref href="GUID-51B3C34F-2F8E-3181-93C4-00F073B1207C.dita"><apiname>MLayDoc</apiname></xref> interface
is used to convey layout information from a text object to the text layout
and views. Within the Symbian platform text content model, global
text and rich text implement this interface. Using such a narrow interface
between content and views allows each to be optimized separately and is good
object-oriented design.</p> <p>A further benefit is that any content model
may be equipped with an <codeph>MLayDoc</codeph> interface. For instance,
an HTML browser would require formatting that could be specified through the <codeph>MLayDoc</codeph> interface,
but for various reasons it may wish to use a substantially different content
model. One important reason is that HTML is essentially read-only. Other applications,
especially for data browsing, may also benefit from the flexibility of the <codeph>MLayDoc</codeph> interface.</p> </section>
<section id="GUID-98AA8A05-676D-44E6-AB34-C9C9AF4D5F0B"><title>Detailed view control</title> <p>The first requirement of
text views is that they honor all the specifications of a text object and
its formatting information. However, in addition to this, text views provides
many flexible features for controlling the display of text.</p> <ul>
<li id="GUID-21B3BAB1-3C84-5E62-8766-9860C00A0E1D"><p>the visibility of non-printing
characters (paragraph marks, blanks, non-breaking blanks) can be controlled</p> </li>
<li id="GUID-EC249206-5F64-599C-9271-6C31EE04194F"><p>background colour can
be specified, and text colour overridden from that in the document, in accordance
with user preferences (e.g., in order to display yellow text on a dark blue
screen instead of the default black on white)</p> </li>
<li id="GUID-C8B6EFC2-4808-584A-82B4-1A386175CEB6"><p>text can have highlighting
applied to it, these highlights may have round corners</p> </li>
<li id="GUID-60812D34-065A-5418-9456-3CCB340ED18B"><p>pictures may have frames,
with or without grab handles, when selected</p> </li>
</ul> </section>
</conbody></concept>