1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-4E985144-C4E6-5114-B88F-B9C92F313D91-GENID-1-8-1-3-1-1-7-1-7-1-6-1" xml:lang="en"><title>The |
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13 control environment</title><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <p>The control environment packages the interface to the window server and |
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15 provides an environment for creating controls. It is implemented in a single |
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16 class, <xref href="GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40.dita"><apiname>CCoeEnv</apiname></xref>, which encapsulates active objects and an |
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17 active scheduler for receiving events from the window server. Each application |
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18 has exactly one <xref href="GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40.dita"><apiname>CCoeEnv</apiname></xref> object which is stored in Thread |
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19 Local Storage (TLS). </p> |
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20 <p> <xref href="GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40.dita"><apiname>CCoeEnv</apiname></xref> also provides a number of utilities which are |
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21 useful to most applications. These utilities include: </p> |
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22 <ul> |
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23 <li id="GUID-E6CC6A2A-2B44-586F-B0B3-5CC8E2862490-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-3-1"><p>creating a graphics |
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24 context, the <keyword>system graphics context</keyword>. This is the standard |
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25 graphics context which is normally used for drawing controls. It may be accessed |
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26 using <codeph>CCoeEnv::SystemGc()</codeph> but controls should get their |
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27 graphics context using <codeph>CCoeControl::SystemGc()</codeph> rather than |
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28 directly from the environment. </p> </li> |
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29 <li id="GUID-7BDF28EF-D209-51E6-B07E-4DB65045D2FE-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-3-2"><p>access to the <keyword>window |
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30 server session</keyword> </p> </li> |
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31 <li id="GUID-028E7FCF-255D-5C82-8100-EDF4F2FCD3B1-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-3-3"><p>utilities for using |
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32 fonts </p> </li> |
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33 <li id="GUID-4CE27203-A304-57C9-BA08-CE523F61582A-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-3-4"><p>utilities for reading |
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34 resource values from <keyword>resource files</keyword> </p> </li> |
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35 <li id="GUID-2875D169-00F7-5C33-AEF7-4C8BB41B74EE-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-3-5"><p>Support for singleton |
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36 (static) objects </p> </li> |
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37 </ul> |
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38 <section id="GUID-C049C06F-8668-44C3-B162-7675CB00515A-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-4"><title>Resource readers and resource files</title> <p> <codeph>CCoeEnv</codeph> maintains |
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39 a list of the resource files used by the application. Files may be added to |
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40 the list using <codeph>AddResourceFileL()</codeph> and removed using <codeph>DeleteResourceFile()</codeph>. </p> <p>The |
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41 utility functions provided by the control environment read resources and resource |
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42 data from the resource files in its list. </p> <p>A resource file consists |
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43 of a list of resources, each identified by a resource ID. Each resource consists |
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44 of a list of resource values in the form of binary data. The order and lengths |
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45 of the values for each resource type are defined in a resource definition |
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46 (generally stored in a file with an <filepath>.rh</filepath> extension). </p> <p>Reading |
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47 data from a resource file requires two stages: </p> <ul> |
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48 <li id="GUID-ADC4F5E4-5FCA-55FA-AB2A-0B607D9350DD-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-4-6-1"><p>read a resource from |
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49 the resource file into a buffer </p> </li> |
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50 <li id="GUID-84FC56CB-F182-52C5-BFA8-79A51ABC4810-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-4-6-2"><p>read values from the |
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51 resource using a resource reader </p> </li> |
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52 </ul> <p> <codeph>CCoeEnv</codeph> provides utility functions to perform the |
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53 first of these stages and functions to create resource readers. </p> <p>An |
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54 application's default resource file, one which has the same name as the application, |
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55 is loaded automatically. </p> <p>It should be noted that stage two can be |
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56 omitted if the resource contains only one value, or if it is read into a formatted |
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57 buffer. In both of these cases the resource data can be read straight from |
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58 the buffer. </p> </section> |
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59 <section id="GUID-4B579429-B1F4-4B8C-9C78-359D2B568303-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-5"><title>Singletons - CCoeStatic</title> <p>The <xref href="GUID-F0C084E2-C683-39E2-A131-77FE3206A02C.dita"><apiname>CCoeStatic</apiname></xref> base |
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60 class is closely associated with <xref href="GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40.dita"><apiname>CCoeEnv</apiname></xref>. Between them |
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61 they allow singleton objects to be created and stored in Thread Local Storage |
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62 (TLS). By doing so they provide an equivalent to writeable global static data. </p> <p>Classes |
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63 derived from <xref href="GUID-F0C084E2-C683-39E2-A131-77FE3206A02C.dita"><apiname>CCoeStatic</apiname></xref> are automatically added to the |
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64 environment when they are instantiated for the first time. Subsequent attempts |
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65 to instantiate an object of the same type will result in a panic (with error |
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66 code <codeph>ECoePanicDuplicateObjectUid</codeph>). </p> <p>Each singleton |
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67 requires a UID and may be given a destruction priority (relative to other |
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68 singletons and the AppUi) and a scope (<codeph>EThread</codeph> or <codeph>EApp</codeph>). </p> <p>Once |
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69 a singleton has been created it may be accessed through the <xref href="GUID-12A9389D-363B-3F54-857F-89EE0EDCDF40.dita"><apiname>CCoeEnv</apiname></xref> API. </p> <codeblock id="GUID-99260739-1E0F-5032-989E-B1D8607ABE2C-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-5-6" xml:space="preserve">// Singleton access |
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70 IMPORT_C static CCoeStatic* Static( TUid aUid ) ; |
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71 IMPORT_C CCoeStatic* FindStatic( TUid aUid ) ;</codeblock> <p> <xref href="GUID-F0C084E2-C683-39E2-A131-77FE3206A02C.dita"><apiname>CCoeStatic</apiname></xref> has |
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72 no public functions. </p> </section> |
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73 <section id="GUID-097FE0A7-2221-46DE-804D-5E25E85F6F96-GENID-1-8-1-3-1-1-7-1-7-1-6-1-2-6"><title>See also</title> <p> <xref href="GUID-7250950C-5502-5ACE-864B-0EFD5C253053-GENID-1-8-1-3-1-1-7-1-10-1.dita">How |
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74 to create a Singleton</xref> </p> </section> |
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75 </conbody></concept> |
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