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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-16A1C613-288D-471C-8551-51B61290E28F" xml:lang="en"><title>Application
+Start-Up Time Optimization</title><shortdesc>It is important that phone users do not have to wait long for applications
+to start. This document summarizes the techniques for optimizing application
+start-up time.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<section>       <title>Introduction</title>       <p>The techniques discussed
+in this document are limited in scope to application programming. In other
+words, they do not require modification of any core OS components or servers.
+Some of the techniques are general good practice and are useful to developers
+at all levels. </p>     <p>The techniques can be summarized as follows:</p><ul>
+<li><p>Avoid causing unnecessary code to be executed as an effect of your
+code.</p></li>
+<li><p>Defer construction of objects, loading of dynamic libraries (for example,
+the application model), and starting servers until you need to use them.</p></li>
+<li><p>Write efficient code!</p></li>
+</ul><note>There is an inevitable trade-off between shortening the start-up
+time and introducing latency elsewhere in the application. For example, if
+you don’t connect to a server at start-up, you will have to do it later on,
+when the application needs to use the server. This may be overcome by a central
+component that coordinates background connections, or construction, such as
+the view server.</note></section>
+<section><title>Measure start-up time before you start optimizing</title><p>Do
+not assume you know which methods take the most time. Pay close attention
+to iterative and recursive operations. Many useful tools and techniques are
+available to help identify poorly performing code:</p><ul>
+<li><p>Software analysis tools, for instance <xref href="http://www.glowcode.com.dita">GlowCode</xref> and
+MetroWerks <xref href="http://www.metrowerks.com/MW/Develop/AMC/CodeTEST/default.htm.dita">CodeTEST</xref></p></li>
+<li><p>The Symbian profiling tool, profiler.exe, which is supplied on DevKits </p></li>
+<li><p>The RDebug class provides some profiling functions </p></li>
+<li><p>The TTime class can be used to time blocks of code, but beware of context
+switches, otherwise you may end up timing other threads!</p></li>
+<li><p>Deliberately slowing down suspect blocks of code can reveal whether
+or not optimizing it would bring a significant performance improvement. </p></li>
+</ul></section>
+<section><title>Defer construction of the application model and other data
+members</title><p>Many applications instantiate their components, for instance
+error handlers, dialogs and menus, during start-up. In turn, each of these
+components may instantiate other components, for instance menu resources and
+icons. This can bring some benefits, for instance reducing application complexity,
+revealing memory allocation problems at start-up rather than after the application
+has been running for some time and improving the runtime performance of the
+application. However, to minimize application start-up time, it is recommended
+to avoid this behavior. Your goal should be to only do what is immediately
+necessary during start-up. </p></section>
+<section><title>Draw the application as quickly as possible</title><p>During
+application start-up, only construct UI components that appear in the application’s
+initial view. This applies especially to the application's implementations
+of <xref href="GUID-05A12A50-93A3-3F3E-842F-81EF47D78F7F.dita#GUID-05A12A50-93A3-3F3E-842F-81EF47D78F7F/GUID-172521B0-E7C8-3214-AA4D-814A9C98216C"><apiname>CXxxApplication::CreateDocumentL()</apiname></xref>, <xref href="GUID-8001206A-3B19-381F-96F6-350336FDFBF2.dita#GUID-8001206A-3B19-381F-96F6-350336FDFBF2/GUID-453AFFB0-6711-3881-97E6-0BB9E5185E06"><apiname>CXxxDocument::ConstructL()</apiname></xref> and <xref href="GUID-8001206A-3B19-381F-96F6-350336FDFBF2.dita#GUID-8001206A-3B19-381F-96F6-350336FDFBF2/GUID-DCC1BAD5-95AB-3308-9132-2780852BA913"><apiname>CXxxDocument::CreateAppUiL()</apiname></xref>, all of which are called before <xref href="GUID-3C72B6B6-F1B3-3C36-B69A-5074E5EDC32A.dita#GUID-3C72B6B6-F1B3-3C36-B69A-5074E5EDC32A/GUID-5C26B1AB-6917-3133-9CD8-34AFCA9524B9"><apiname>CXxxAppUi::ConstructL()</apiname></xref>.
+Do not read bitmaps, resources, or any other data associated with the UI from
+files unless it is necessary.</p><p>In <xref href="GUID-3C72B6B6-F1B3-3C36-B69A-5074E5EDC32A.dita#GUID-3C72B6B6-F1B3-3C36-B69A-5074E5EDC32A/GUID-5C26B1AB-6917-3133-9CD8-34AFCA9524B9"><apiname>CXxxAppUi::ConstructL()</apiname></xref>,
+make sure <xref href="GUID-6965379F-00B9-38DB-9AF3-9DAD55DEBBB7.dita"><apiname>ActivateL()</apiname></xref> and <xref href="GUID-0F226BB0-2D2F-3BD5-A439-C25F7DEACE85.dita"><apiname>DrawNow()</apiname></xref> are
+called on all controls that must be drawn when the application is launched.
+Also ensure that the client-side window server command buffer is flushed by
+calling <xref href="GUID-09D06EF8-E231-3A76-A4F0-267B9CD83B54.dita"><apiname>Flush(</apiname></xref>) on the application's window server session.
+This ensures that there aren't any drawing commands left in the client-side
+buffer, after <xref href="GUID-0F226BB0-2D2F-3BD5-A439-C25F7DEACE85.dita"><apiname>DrawNow()</apiname></xref> has completed. </p></section>
+<section><title>Minimize the number of bitmaps used by GUI components</title><p>Often,
+when a large number of small images are required by an application, the overhead
+associated with loading each bitmap outweighs any benefit associated with
+their size. Some possible ways to avoid this are: </p><ul>
+<li><p>use text instead, </p></li>
+<li><p>for very simple graphics, draw directly using drawing primitives rather
+than loading a bitmap,  </p></li>
+<li><p>concatenate many small bitmaps into one large bitmap file to reduce
+the need to search for and load multiple files.</p></li>
+</ul></section>
+<section><title>Reduce the number of redraws</title><p>Some GUI components
+redraw themselves every time their data changes. This may not always be necessary.
+Complicated GUI components should implement their <xref href="GUID-AC3B79CA-A2FE-395E-9BCE-4630AF6910AC.dita"><apiname>Draw()</apiname></xref> method
+to only update the area of the screen that has changed. For example, there
+is no point in redrawing a whole list box every time a new item is appended
+to it. In such cases, a GUI API should allow you to switch off redrawing.
+Beware of GUI methods that cause the object they are called upon to redraw
+itself.</p><p>Use <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-811046A4-4272-3B29-80D9-CB897C4E1DD0"><apiname>CCoeControl::DrawDeferred(</apiname></xref>) in preference
+to <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-70FF46AE-5ACC-36F1-97F0-CBD847779C19"><apiname>CCoeControl::DrawNow(</apiname></xref>) if possible, because excessive
+use of <xref href="GUID-65BA28DB-77C6-3075-80E7-84E98780FD19.dita"><apiname>DrawNow(</apiname></xref>) can cause GUI flicker. For an explanation,
+see the documentation for <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-9FB682AC-0209-302A-83F3-7BCB1162B998"><apiname>CCoeControl::DrawDeferred()</apiname></xref>. </p></section>
+<section><title>Use ROM-based bitmaps rather than filestore bitmaps</title><p>Uncompressed
+ROM-based bitmaps that can be used in place from ROM are approximately three
+times faster to use than filestore bitmaps. Using them can bring a significant
+reduction in application start-up time.   </p><p>Specifying bitmap= instead
+of file= in the .OBY and .IBY files when building the ROM causes bitmaps to
+be uncompressed before inclusion in the ROM. Other bitmaps need to be uncompressed
+at runtime, which impacts performance.   </p><p>The drawback of such bitmaps
+is that they are large (up to 3 times larger than file based) and cannot be
+compressed, although decompressing bitmaps should probably be avoided during
+start-up anyway due to the extra processing required.   </p><p>If ROM space
+is limited, consider using such ROM-based bitmaps only if they are displayed
+during application start-up. </p></section>
+<section><title>Color depth matching</title><p>When bitmaps are drawn to the
+screen, optimum performance is achieved by ensuring that:</p><codeph>Bitmap
+color depth = Window color depth = Screen device color depth </codeph><p>If
+this is the case, no palette mapping between the different color depths is
+needed. On real hardware, this optimization has been found to improve drawing
+speed by up to ten times. However, in order to match the screen
+and window color depth, bitmaps may need to increase in size and so this optimization
+is only possible if the increase in ROM or RAM usage is acceptable. </p></section>
+<section><title>Minimize access to the file system</title><p>The file server
+can be a major bottleneck during start-up when virtually all threads are searching
+for and loading data, libraries and plug-ins. Therefore reducing file access
+is one of the most effective ways to improve performance. </p></section>
+<section><title>Minimize the use of resource files</title><p>Resource files
+are used for localization and allow modifications to be made to an application
+without the need to rebuild it, but they are expensive to use because they
+require access to the file system. </p></section>
+<section><title>Do not specify a default document filename for non document-based
+applications</title><p>Many applications on a smartphone do not need to use
+documents, for example Telephony, Contacts (this uses the contacts database),
+Browser and Messaging.   </p><p>By not specifying a default document filename,
+hundreds of milliseconds can potentially be saved from such applications'
+start-up time.   </p><p>If an application uses a document file, application
+start-up may involve the following steps: </p><ul>
+<li><p>reading the name of the last used document file from the application’s
+.ini file,</p></li>
+<li><p>opening the document file, or if one doesn't exist, creating a default
+document file, after reading its name from the application's resource file, </p></li>
+<li><p>writing the name of the last used file to the application’s .ini file
+(which is created if it doesn’t exist),  </p></li>
+<li><p>writing an entry to the most recently used file list (mru.dat), </p></li>
+<li><p>additional document-related processing within <xref href="GUID-96CA3B4B-993F-36C0-9A5B-DF5CC74EE20E.dita#GUID-96CA3B4B-993F-36C0-9A5B-DF5CC74EE20E/GUID-E2A40307-6EB6-3ABC-B97A-63B77F565CCF"><apiname>CEikonEnv::ConstructAppFromCommandLineL()</apiname></xref>. </p></li>
+</ul><p>The default document's name is read from the application's resource
+file by <xref href="GUID-1185F595-0488-3E93-8D60-6B3A1A3AC32E.dita#GUID-1185F595-0488-3E93-8D60-6B3A1A3AC32E/GUID-5D851D0B-6399-3BD8-ADB5-63AD48494D47"><apiname>CEikAppUi::ProcessCommandParametersL()</apiname></xref>. There are
+two ways of preventing the application from using a default document file: </p><ul>
+<li><p>Give the default document a NULL name in the resource file:</p><codeph>RESOURCE
+TBUF { buf=""; }</codeph></li>
+<li><p>Override <xref href="GUID-1185F595-0488-3E93-8D60-6B3A1A3AC32E.dita#GUID-1185F595-0488-3E93-8D60-6B3A1A3AC32E/GUID-5D851D0B-6399-3BD8-ADB5-63AD48494D47"><apiname>CEikAppUi::ProcessCommandParametersL()</apiname></xref> to
+zero the document name and return EFalse. This method is slightly more efficient
+because it avoids reading the default document name from the resource file
+altogether: </p><codeblock xml:space="preserve">TBool CMyAppUi::ProcessCommandParametersL(TApaCommand /*aCommand*/, TFileName&amp; aDocumentName, const TDesC8&amp; /*aTail*/){aDocumentName.Zero();return EFalse;}</codeblock></li>
+</ul></section>
+<section><title>Drive scanning</title><p>This can be a cause of unnecessary
+file server use.   </p><p>To prevent excessive drive access and scanning,
+always specify a drive letter in file paths, if known. The omission of a drive
+letter will cause all available drives to be searched in the standard Symbian
+OS order, in which Z: is always searched last. </p></section>
+<section><title>Only make server requests if you need to</title><p> Server
+requests involve context switching and may cause the server to run instead
+of the application. In the worse case if you make a request to a server that
+has not yet been started you may cause the server to start. This will involve
+creating a new thread (and possibly process) and running any server initialization
+code.</p></section>
+<section><title>Use asynchronous server requests instead of synchronous server
+requests</title><p> Synchronous operations or methods (particularly for server
+requests) can cause general application slowness, and in particular, a significant
+reduction in responsiveness. Synchronous requests to servers mean your thread
+is waiting, so that no start-up progress is being made.   </p><p>No 'Golden
+Rule' exists about when to avoid synchronous requests. However, if an asynchronous
+version of a method exists, it is a good indication that the synchronous method
+could potentially take some time. Whilst it may take a little extra effort
+to handle asynchronous versions of method calls, you should consider very
+carefully any decision to use the synchronous version. It’s often easier to
+change from using an asynchronous version to synchronous than vice versa. 
+ </p><p>Note that in some situations, you might know that the server is implementing
+your asynchronous request synchronously. If this is the case, and the server
+runs with a higher priority than your application, then both versions of the
+API may have the same performance. However, using the synchronous version
+in this case has the drawback that it relies upon knowledge of the server's
+implementation, which could potentially change. </p></section>
+<section><title>Do not repeatedly open and close connections to the same server</title><p> Opening
+a connection to a server is an expensive operation. If an application uses
+a server frequently then it should create one connection and leave it open
+until the application is destroyed. R classes declared as temporaries (on
+the stack, in other words) within a method may be a sign of this behavior. </p></section>
+</conbody></concept>
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