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<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>