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<concept id="GUID-0C3A4156-E5CF-55F9-91A0-A7961FDEE030" xml:lang="en"><title>LCD Extension Architecture</title><shortdesc>This topic describes the architecture of the LCD Extension. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>The LCD Extension (or video driver) is implemented as a standard
kernel extension and is loaded by the kernel at boot time. </p>
<p>The public interface to the LCD Extension is accessed through the
User-Side Hardware Abstraction (HAL) interfaces <xref href="GUID-BD00E7FC-C234-3111-87A5-10F79EB0F2B8.dita#GUID-BD00E7FC-C234-3111-87A5-10F79EB0F2B8/GUID-573C49D6-7763-37AE-B2B2-4C8FB1327E21"><apiname>HAL::Get()</apiname></xref> and <xref href="GUID-BD00E7FC-C234-3111-87A5-10F79EB0F2B8.dita#GUID-BD00E7FC-C234-3111-87A5-10F79EB0F2B8/GUID-9454F1B2-D525-3D6D-A872-C6457CACD4FC"><apiname>HAL::Set()</apiname></xref>. The LCD Extension registers itself
with the kernel as the handler for the <xref href="GUID-7F299BFC-D8A5-3A5A-B8DA-39BF42C99DC6.dita"><apiname>EHalGroupDisplay</apiname></xref> function group and implements the functions. </p>
<p>From Symbian^3 there is a new graphics architecture called <xref href="GUID-D93978BE-11A3-5CE3-B110-1DEAA5AD566C.dita">ScreenPlay</xref>. When ScreenPlay is in use, the <xref href="GUID-4C166A49-31F7-5315-B797-F97DB52600BC.dita">Display Channel Driver</xref> can provide a logical device driver proxy between the Composition
Implementation and the LCD Extension. However, the use of the Display
Channel Driver is optional and implementers may decide not to use
it. </p>
<p>When ScreenPlay is not in use, the Graphics <xref href="GUID-9E7D563E-9FFB-5FA9-8944-9CBAC281FDD2.dita">Screen Driver component</xref> is a client of the LCD Extension. The Screen Driver is platform-specific
and must be ported by the device creator. </p>
<p>The Text Window Server also implements a version of the Screen
Driver for a simple console user interface. </p>
</conbody><related-links>
<link href="GUID-D93978BE-11A3-5CE3-B110-1DEAA5AD566C.dita"><linktext>The
ScreenPlay Graphics                 Architecture</linktext></link>
<link href="GUID-F64E6551-670E-5E12-8103-DE504D3EC94F.dita"><linktext>The
Non-ScreenPlay                 Graphics Architecture</linktext></link>
<link href="GUID-4C166A49-31F7-5315-B797-F97DB52600BC.dita"><linktext>Display
Channel Driver</linktext></link>
<link href="GUID-9E7D563E-9FFB-5FA9-8944-9CBAC281FDD2.dita"><linktext>Screen
Driver                 Component</linktext></link>
</related-links></concept>