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<concept id="GUID-37E8A48E-09B8-5958-9263-B33EDAE3F7C6-GENID-1-8-1-6-1-1-4-1-6-1-3-1" xml:lang="en"><title>UI

Control Framework Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-4DB4AA3B-1CC9-4829-9146-B07BBDDEBAC5-GENID-1-8-1-6-1-1-4-1-6-1-3-1-2-1"><title>Architectural

relationships</title> <p>The control framework provides an abstract middle

layer between the low-level windowing functionality, provided by the Window

Server, and concrete user interface classes provided by UIKON and UI variant-specific

libraries. </p> <p>Application developers use the API directly to create their

own controls and indirectly through derived classes provided by UIKON and

AVKON. </p> <fig id="GUID-DD81BA7E-07D0-53C7-9B42-7BE263CC82D3-GENID-1-8-1-6-1-1-4-1-6-1-3-1-2-1-4">

<title>              Cone architectural relationships            </title>

<image href="GUID-63BB9C30-9103-5900-9FD7-5B45FD78A5D7_d0e51074_href.png" placement="inline"/>

</fig> </section>

<section id="GUID-9A9F72A2-0CA0-488A-91DE-35FD0A88B6CD-GENID-1-8-1-6-1-1-4-1-6-1-3-1-2-2"><title>Description</title> <p><b>Controls</b> </p> <p>A

control is a rectangular area of a window that may respond to user input.

Controls have a number of properties that determine their behavior and their

relationships to other controls and windows. </p> <p>A control is represented

by the class <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita"><apiname>CCoeControl</apiname></xref>. </p> <p>A <b>simple control</b> is

one which contains no other controls. </p> <p>A <b>container control</b> is

one which contains one or more controls. A container control is also referred

to as a <b>compound control</b>. The contained controls may themselves be

container controls. When a control is contained in a container control it

is called a <b>component control</b>. A component control is always redrawn

when its container control is redrawn. </p> <p>The following diagram shows

simple controls in orange and container controls in grey. </p> <fig id="GUID-771A429A-B61E-5C45-83A9-4B9F76C40FB9-GENID-1-8-1-6-1-1-4-1-6-1-3-1-2-2-8">

<title>                 Simple and compound controls               </title>

<image href="GUID-8B37A2C7-B4DB-5826-B6C2-3C21012EF9EA_d0e51123_href.png" placement="inline"/>

</fig> <p><b>Controls and Windows </b> </p> <p>A window may be considered

as a transparent layer. Windows are managed by the Window Server and described <xref href="GUID-0C4B86B5-530A-5839-86C1-46E7ABE281E0.dita">elsewhere</xref>. A control

provides a means of access to a window - it can be drawn onto the window and

can receive input. </p> <p>Each window has a one-to-one relationship with

a single control that covers it precisely. This control is referred to as

a <b>window-owning control</b>. A window-owning control shares the behavior

of its window, in particular the parent-child window relationships which govern

the window's position and overlapping behavior. </p> <p>A <b>non-window-owning

control</b> typically covers only part of a window. It cannot be moved around

on the screen independently of its window, cannot draw outside its window

and is always a component control. </p> <p>You might think of a window-owning

control as a piece of glass and a non-window-owning control as a sticker on

a window-owning control. </p> <p><b>Application User Interface (AppUi) framework</b> </p> <p>The

application user interface framework provides support for the distribution

of key events to an application's controls. It maintains a control stack to

which an application must add all the top-level container controls that it

wishes to handle key events, setting a priority for each. When a key event

occurs, the framework offers it to each control on the stack in priority order

until it is consumed. </p> <p>The application user interface framework is

provided by the base class <xref href="GUID-3AC2CDAC-0291-309F-A020-049BC9F2CF90.dita"><apiname>CCoeAppUi</apiname></xref>. UIKON and UI variants

specialize <codeph>CCoeAppUi</codeph> further. Applications derive from the

variant AppUi. </p> <p> <xref href="GUID-3AC2CDAC-0291-309F-A020-049BC9F2CF90.dita"><apiname>CCoeAppUi</apiname></xref> provides a simplified

interface to the <xref href="GUID-830E40D0-7DEE-5EFB-BCC6-EC0AA7FF7A02.dita">View

Server</xref> which enables seamless switching between different views across

various applications. </p> <p><b>Control Environment (CoeEnv)</b> </p> <p>The

Control Environment simplifies the interface to the Window Server and provides

an environment for creating controls. It is a single instance (a singleton)

of the class <xref href="GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40.dita"><apiname>CCoeEnv</apiname></xref> which encapsulates an active scheduler

and active objects for communicating with the window server. <xref href="GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40.dita"><apiname>CCoeEnv</apiname></xref> is

created automatically by the framework and a pointer stored in Thread Local

Storage (TLS). It is available through <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-BB8AF6C8-F7C8-3478-858A-4E2C68DF1B7A"><apiname>CCoeControl::CoeEnv()</apiname></xref>, <xref href="GUID-3AC2CDAC-0291-309F-A020-049BC9F2CF90.dita#GUID-3AC2CDAC-0291-309F-A020-049BC9F2CF90/GUID-6D8B3C54-087B-36C6-81A4-E07E92AA9D72"><apiname>CCoeAppUi::CoeEnv()</apiname></xref> and

through its own static function, <xref href="GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40.dita#GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40/GUID-7A9CB8EE-520A-30E2-BA54-5BEFBB56717F"><apiname>CCoeEnv::Static()</apiname></xref>, which

is less efficient. </p> <p>The control environment also provides simplified

access to drawing functions, fonts, and resource files which are used by most

applications. </p> </section>

<section id="GUID-060D338D-BADE-46A6-B7B1-DB28F07B39D3-GENID-1-8-1-6-1-1-4-1-6-1-3-1-2-3"><title>See also</title> <ul>

<li><p><xref href="GUID-1C802DBD-1453-5C69-94D5-FB0229C544D6.dita">Uikon Overview</xref></p></li>

<li><p><xref href="GUID-830E40D0-7DEE-5EFB-BCC6-EC0AA7FF7A02.dita">View Server

Overview</xref></p></li>

<li><p><xref href="GUID-0C4B86B5-530A-5839-86C1-46E7ABE281E0.dita">Window Server</xref></p></li>

<li><p><xref href="GUID-EEAB5A2F-AD1F-57B9-98AA-20DEEA23C3C2.dita">Asynchronous

Programming (active scheduler &amp; active objects)</xref></p></li>

</ul></section>

</conbody></concept>