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    12 <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>

    13 <p>The LCD Extension (or video driver) is implemented as a standard

    14 kernel extension and is loaded by the kernel at boot time. </p>

    15 <p>The public interface to the LCD Extension is accessed through the

    16 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

    17 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>

    18 <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

    19 Implementation and the LCD Extension. However, the use of the Display

    20 Channel Driver is optional and implementers may decide not to use

    21 it. </p>

    22 <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

    23 and must be ported by the device creator. </p>

    24 <p>The Text Window Server also implements a version of the Screen

    25 Driver for a simple console user interface. </p>

    26 </conbody><related-links>

    27 <link href="GUID-D93978BE-11A3-5CE3-B110-1DEAA5AD566C.dita"><linktext>The

    28 ScreenPlay Graphics                 Architecture</linktext></link>

    29 <link href="GUID-F64E6551-670E-5E12-8103-DE504D3EC94F.dita"><linktext>The

    30 Non-ScreenPlay                 Graphics Architecture</linktext></link>

    31 <link href="GUID-4C166A49-31F7-5315-B797-F97DB52600BC.dita"><linktext>Display

    32 Channel Driver</linktext></link>

    33 <link href="GUID-9E7D563E-9FFB-5FA9-8944-9CBAC281FDD2.dita"><linktext>Screen

    34 Driver                 Component</linktext></link>

    35 </related-links></concept>