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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 id="GUID-4585EAA0-4169-4C5C-A7AD-AAA7FDA529C6">       <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 id="GUID-818EB735-F408-47D9-9759-A180766996B4"><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 id="GUID-594EC7CB-3477-4D0F-B489-8C1A42ED0789"><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 id="GUID-F7BE9B30-1993-4736-9E88-F0E065BE1A3C"><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 <codeph>CXxxApplication::CreateDocumentL()</codeph>, <codeph>CXxxDocument::ConstructL()</codeph> and <codeph>CXxxDocument::CreateAppUiL()</codeph>, all of which are called
+before <codeph>CXxxAppUi::ConstructL()</codeph>. Do not read bitmaps, resources,
+or any other data associated with the UI from files unless it is necessary.</p><p>In <codeph>CXxxAppUi::ConstructL()</codeph>,
+make sure <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-C79D0B6F-C2D7-3F22-A62B-88762092E869"><apiname>CCoeControl::ActivateL()</apiname></xref> and <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-D5458F8C-E199-37DD-B821-050B749122C6"><apiname>CCoeControl::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 <codeph>Flush()</codeph> 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-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-D5458F8C-E199-37DD-B821-050B749122C6"><apiname>CCoeControl::DrawNow()</apiname></xref> has completed. </p></section>
+<section id="GUID-B320F7A3-C0E3-4A3D-8B45-AEFEDFBAAD2E"><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 id="GUID-F00BA3FF-D9BD-44DF-A284-BAF5701179D8"><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<codeph>Draw()</codeph> 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-9FB682AC-0209-302A-83F3-7BCB1162B998"><apiname>CCoeControl::DrawDeferred()</apiname></xref> in
+preference to <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-D5458F8C-E199-37DD-B821-050B749122C6"><apiname>CCoeControl::DrawNow()</apiname></xref> if possible, because
+excessive use of <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-D5458F8C-E199-37DD-B821-050B749122C6"><apiname>CCoeControl::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 id="GUID-71443827-BF8D-4BD8-8136-5023B6D65204"><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 id="GUID-5FFD3311-DF8D-4EB1-9C76-EB9F3D306655"><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 id="GUID-5E89E812-4B22-4B5C-A5E4-5FBE6619DC25"><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 id="GUID-9218ABF0-4062-439A-A5E9-273D76D4B711"><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 id="GUID-C1CCFD4F-5C63-47C4-A312-38ACB5C16676"><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 id="GUID-2DF939E2-C30C-4A84-90DC-92234BEB6AA0"><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 platform order, in which Z: is always searched
+last. </p></section>
+<section id="GUID-C555545B-977F-490D-A7A7-5B6D0D0AD889"><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 id="GUID-1E571A30-5D8A-4647-939E-EF79B033B88E"><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 id="GUID-4C7697BD-2898-4E1E-AA88-41E9F3CE2603"><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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