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<concept id="GUID-DD15F24B-0786-4531-A6C5-A5E70EBE2732" xml:lang="en"><title>Layout
change events</title><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>Layout change events are generated when the screen size or layout is
changed. The Symbian platform supports multiple screen resolutions (<xref href="GUID-B02C762B-C452-4184-ABEA-4753E6CD47D2.dita">scalable UI</xref>). Thus,
layout awareness is particularly crucial for those applications that implement
a customized UI instead of using automatically scalable Avkon UI components.
Applications can detect the changes in layout with, for example, the following
methods:</p>
<ul>
<li><p>Controls can override the <xref href="jar:GUID-35228542-8C95-4849-A73F-2B4F082F0C44.jar!/sdk/doc_source/reference/reference-cpp/Control_Environment/CCoeControlClass.html#%3a%3aCCoeControl%3a%3aHandleResourceChange%28TInt%29" format="application/java-archive"><parmname>CCoeControl::HandleResourceChange()</parmname></xref> to detect the <parmname>KEikDynamicLayoutVariantSwitch</parmname> message.</p>
</li>
<li><p>UI controllers can override the <xref href="jar:GUID-35228542-8C95-4849-A73F-2B4F082F0C44.jar!/sdk/doc_source/reference/reference-cpp/Control_Environment/CCoeControlClass.html#%3a%3aCCoeControl%3a%3aHandleResourceChange%28TInt%29" format="application/java-archive"><parmname>CCoeControl::HandleResourceChange()</parmname></xref> to detect the <parmname>KEikDynamicLayoutVariantSwitch</parmname> message. </p>
</li>
</ul>
<p>The following example code demonstrates the implementation of <parmname>HandleResourceChange()</parmname>:</p>
<codeblock id="GUID-8BF5353E-F09F-457A-826A-3F83ADEDF97E" xml:space="preserve">void CExampleControl::HandleResourceChange( TInt aType )
    {
    CCoeControl::HandleResourceChange(aType);
    //call base class implementation
    if( aType==KEikDynamicLayoutVariantSwitch )
        {
        TRect rect;
        // ask where container's rectangle should be
        // EMainPane equals to area returned by
        //CEikAppUi::ClientRect()
        AknLayoutUtils::LayoutMetricsRect( AknLayoutUtils::EMainPane,rect );
        SetRect( rect );
        }
    }
</codeblock>
<p>The following example code demonstrates the implementation of <parmname>HandleResourceChangeL()</parmname>:</p>
<codeblock id="GUID-226A9867-C4C5-4286-B324-30EB17A4374D" xml:space="preserve">void CExampleAppUi::HandleResourceChangeL( TInt aType )
    {
    CAknAppUi::HandleResourceChangeL( aType );
    if( aType == KEikDynamicLayoutVariantSwitch )
        {
        // do the re-layout of the components
        }
    // Controls derived from CCoeControl, handled in a
    // container class
    iExampleControlContainer-&gt;HandleResourceChange( aType );
    //Must not call this if the components are on the control stack
    //iView-&gt;HandleResourceChangeL( aType );
    }
</codeblock>
<p>If <parmname>iExampleControlContainer</parmname> is added to the control
stack, it will get its <parmname>HandleResourceChange()</parmname> called
when a layout is switched and there is no need to call it explicitly. </p>
<p>For a reference design of a layout-aware application using a custom
UI, refer to the <i>S60 Platform: Scalable Screen-Drawing Example</i> available
for download from <xref href="http://www.forum.nokia.com/info/sw.nokia.com/id/c5b4228b-992c-4636-8f48-753040760391/S60_Platform_Scalable_Screen_Drawing_Example_v1_3_en.zip.html" scope="external">Forum Nokia</xref>.</p>
</conbody></concept>