1999-03-23 07:27:30 +00:00
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="GENERATOR" content="Mozilla/4.51 [en] (X11; U; Linux 2.0.36 i686) [Netscape]">
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<meta name="Author" content="Suresh Duddi">
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<title>XPCOM Code FAQ</title>
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<h2>
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XPCOM Code FAQ</h2>
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Suresh Duddi <<a href="mailto:dp@netscape.com">dp@netscape.com</a>>
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<br>Last Modified: March 22 1999
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<br>
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<hr WIDTH="100%">
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<br>I am documenting things randomly as I am replying to people's questions.
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So this might look more like an FAQ.
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<h4>
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What are the Global Objects that XPCOM maintains</h4>
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<ul>mGlobalServiceManager
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<br>mGlobalComponentManager</ul>
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<h4>
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What are the static classes that XPCOM maintains</h4>
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<blockquote>nsComponentManager
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<br>nsServiceManager</blockquote>
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<h4>
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Is there any restriction on which static class I should call first</h4>
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<blockquote>No restrictions. You can call any function from the static
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classes nsComponentManager and nsServiceManager. XPCOM will do the right
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1999-03-23 08:04:18 +00:00
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thing to initialize itself at both places.
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<p>Autoregistration() can happen only after Init_XPCOM() is called since
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the registy might be required by SelfRegister() functions of the dlls and
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it is only in Init_XPCOM() do we create register the RegistryFactory()
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with the ComponentManager.</blockquote>
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1999-03-23 07:27:30 +00:00
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<h4>
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What is the order of creation of the ServiceManager, ComponentManager and
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Registry</h4>
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<blockquote>Init_XPCOM()
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1999-03-23 08:04:18 +00:00
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<blockquote>
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<li>
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create the global component manager</li>
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<li>
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create the global component manager and register as service with the global
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service manager</li>
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<li>
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RegisterFactory(...RegistryFactory...) Register the RegistryFactory()
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with the component manager so that new registry objects can be created.</li>
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</blockquote>
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Now the hard problem is when to trigger Init_XPCOM() There are two static
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1999-03-23 07:27:30 +00:00
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objects nsComponentManager and nsServiceManager. Any function in either
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of them can be called first. Today nsServiceManager::GetService() is the
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first one that gets called. All the members of the static nsServiceManager
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use the nsGetGlobalServiceManager() to get to the global service manager.
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All members of the static nsComponentManager use the nsGetGlobalComponentManager()
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to get to the global component manager. Hence if we trigger Init_XPCOM()
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from both NS_GetGlobalComponentManager() and NS_GetGlobalServiceManager()
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we will be safe.</blockquote>
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1999-03-23 08:04:18 +00:00
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<h4>
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Is there a global Registry being maintained</h4>
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<blockquote>No. The nsIRegistry is designed to be lightweight access to
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the registry. Consumers who need to access the registry should use the
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component manager to create the their own registry access object. This
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is required because the open() call is supported by the nsIRegistry() and
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if we maintain a global registry arbitrating which registry file is opened
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is going to be a major headach.
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<p>The ProgID for the registry will be <font color="#990000">component://netscape/registry</font></blockquote>
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1999-03-23 07:27:30 +00:00
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<hr WIDTH="100%">
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</body>
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</html>
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