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<concept id="GUID-22E46647-D677-5A47-A7E0-E1E0AE736B27" xml:lang="en"><title>DirectGDI
Adaptation Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>The DirectGDI Adaptation component, together with the DirectGDI Interface
component, forms the DirectGDI adaptation layer. The DirectGDI Interface component
defines the interfaces that the adaptations must implement and the DirectGDI
Adaptation component consists of the two DirectGDI implementations that are
provided in the Graphics package. </p>
<p><b>Target audience</b>: Device creators. </p>
<note type="note">DirectGDI is deprecated in Symbian^3.</note>
<p>The <xref href="GUID-A2E07A3C-B3A8-50B9-BD60-F1F01795FA24.dita">DirectGDI component</xref> provides
a framework that enables graphics hardware acceleration and interleaved rendering.
This framework provides an API for client applications and a Hardware Adaptation
Interface (HAI), which defines interfaces that must be implemented by device
and hardware manufacturers in order to provide the API functionality. The
framework has a dependency on the <xref href="GUID-82B0B4B9-6BC2-5BEF-B3B0-D57AC57F8D8A.dita">Graphics
Resource Component</xref>. </p>
<p>The Graphics package includes two DirectGDI adaptations: </p>
<ul>
<li id="GUID-B0C72AE2-2A06-59AD-98AA-BCE881ECD460"><p>A purely software adaptation
that uses existing components to draw to the screen in a similar manner to
BitGDI. This is suitable for use in phones that do not include graphics acceleration
hardware. </p> </li>
<li id="GUID-FB34D088-0046-5A1B-9C23-39D11C448ECD"><p>A hardware adaptation
that uses OpenVG and EGL APIs on the H4 platform. This is provided for reference
purposes and there is no requirement that the implementation use OpenVG. Hardware
manufacturers can in fact use any third-party rendering system that is suitable
for use with the target hardware. </p> </li>
</ul>
<p>The following diagram shows the generic DirectGDI API and implementation,
with one software and two hardware implementations. Although shown on the
same diagram, in fact only one implementation can exist on the same phone.
A configuration at ROM build time decides which implementation is used. </p>
<fig id="GUID-E4CD5B76-03E0-5F4C-8C65-C2F2B52969F5">
<title>           DirectGDI architecture          </title>
<image href="GUID-912643B5-0B8D-5836-B864-9A2DBAC86B00_d0e271062_href.png" placement="inline"/>
</fig>
<p>Notice that all three of the implementations implement the common <xref href="GUID-97E3E8DD-A2DA-3961-96E3-41AEAFFDD275.dita"><apiname>MDirectGdiEngine</apiname></xref> interface.
Also notice that the hardware implementation uses asynchronous calls to the
graphic acceleration hardware driver. This means that the CPU can continue
with other processing while the GPU is busy processing the rendering request.
This improves the parallelism between the CPU and the GPU. </p>
<p>The software implementation does not use asynchronous calls, because the
rendering is performed by the CPU. </p>
<section id="GUID-134818CD-B113-4AE1-8C48-CDF9CB38C46E"><title>Generic layer</title> <p>The
following figure shows the classes in the DirectGDI generic layer (which is
shaded green). Classes that are provided by other components are shown in
red. Classes that cross the generic layer boundary have some parts that cannot
be modified (such as a fixed API), but have other parts that can be modified. </p> <fig id="GUID-1A830274-D596-586A-B469-0CB7619FB391">
<title>              The DirectGDI generic layer classes            </title>
<image href="GUID-26B3BB7B-53CC-518F-85DA-CBAAD52DCE1C_d0e271087_href.png" placement="inline"/>
</fig> </section>
</conbody><related-links>
<link href="GUID-A2E07A3C-B3A8-50B9-BD60-F1F01795FA24.dita"><linktext>DirectGDI
Component</linktext></link>
<link href="GUID-7B511CC2-CE38-5888-AF12-3568BEB416A6.dita"><linktext>DirectGDI
Interface Component</linktext></link>
<link href="GUID-EBE2D1D3-3A99-54BF-B5C0-08E9267F5750.dita"><linktext>Creating
a DirectGDI Adaptation</linktext></link>
</related-links></concept>