зеркало из https://github.com/mozilla/gecko-dev.git
Added progid spec
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dp%netscape.com
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@ -3,7 +3,7 @@
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="Author" content="Suresh Duddi">
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<meta name="GENERATOR" content="Mozilla/4.5 [en] (WinNT; U) [Netscape]">
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<meta name="GENERATOR" content="Mozilla/4.51 [en] (X11; U; Linux 2.0.36 i686) [Netscape]">
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<title>XPCOM Dynamic Component Registration</title>
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</head>
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<body>
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@ -43,45 +43,35 @@ The Registry provides persistent storage of hierarchical keys and name-value
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pairs associated with each key. Each key also keeps a default value.
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<p>XPCOM will use the following registry hierarchy:
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<blockquote><tt>ROOTKEY_COMMON</tt>
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<br><tt> Classes</tt>
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<br><tt> CLSID</tt>
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<br><tt> Common - Classes - CLSID</tt>
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<br><tt> <b><font color="#CC0000">{108d75a0-bab5-11d2-96c4-0060b0fb9956}</font></b></tt>
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<br><tt>
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"<i>CLSID-string"</i></tt>
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<br><tt>
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ClassName "<i>class name</i>"</tt>
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<br><tt><i>
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</i>
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ProgID "<i>component.class.version"</i></tt>
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<br><tt>
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<i>
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</i>InprocServer "<i>full-path-name"</i></tt>
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<p><tt> "<i>component.class.version"</i></tt>
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InprocServer (S) = <font color="#CC0000">libnfs-protocol.so</font></tt>
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<br><tt>
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CLSID <i>"CLSID-string"</i></tt>
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<p><tt><i> </i>DefaultPathList
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<i>"semicolon separated path list"</i></tt>
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<br><tt><i> </i>Software</tt>
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<br><tt> Netscape</tt>
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ProgID (S) = <b><font color="#CC0000">component://netscape/network-protocol&type=nfs</font></b></tt>
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<br><tt>
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XPCOM</tt>
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<br><tt>
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"<i>full-path-name"</i></tt>
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<br><tt>
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LastModTimeStamp <i>time-value</i></tt>
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<br><tt>
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FileSize <i>nbytes</i></tt>
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<br><tt>
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ComponentsCount "<i>components-count"</i></tt></blockquote>
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ClassName (S) = <b><font color="#CC0000">NFS Protocol
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Handler</font></b></tt>
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<p><tt> <font color="#CC0000">component://netscape/network-protocol&type=nfs</font></tt>
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<br><tt>
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CLSID (S) = <font color="#CC0000">{108d75a0-bab5-11d2-96c4-0060b0fb9956}</font></tt>
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<p><tt><i> </i>Software - Netscape - XPCOM</tt>
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<br><tt> VersionString
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(S) = <font color="#CC0000">alpha0.20</font></tt>
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<p><tt> <font color="#CC0000">libnfs-protocol.so</font></tt>
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<br><tt>
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ComponentsCount (S) = <font color="#CC0000">1</font></tt>
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<br><tt>
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FileSize (S)
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= <font color="#CC0000">78965</font></tt>
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<br><tt>
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LastModTimeStamp (S) = <font color="#CC0000">Wed Feb
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24 11:24:06 PST 1999</font></tt></blockquote>
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<p><br><tt><sup><font color="#990000">*</font> </sup></tt>Automatically
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added by the Repository
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<br>
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<h3>
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<a NAME="The Repository: Object instance creation"></a>The Repository:
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Object instance creation</h3>
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All object creation happens via The Repository. <tt>nsIRepository::CreateInstance()</tt>
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All object creation happens via The Repository. <tt>nsIRepository::CreateInstance()</tt>
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will be the primary way of creation of object instances. The steps in instantiation
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of an object that implements the IID interface and of class CLSID is as
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follows:
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@ -90,10 +80,8 @@ follows:
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The CLSID of the component that would need to create the object instance
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is identified.</li>
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<ol>If the input to <tt>nsIRepository::CreateInstance() </tt>is a CLSID,
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then there is no figuring out. If the input is a ProgID string, it uses
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<tt>nsIRepository::ProgIDToCLSID()</tt>
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to convert the ProgID string passed into it to convert to the CLSID.</ol>
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<ol>Callers use <tt>nsIRepository::ProgIDToCLSID()</tt> to convert the
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ProgID string to the CLSID.</ol>
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<li>
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Load the dll associated with the CLSID after consulting the Registry</li>
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@ -101,8 +89,7 @@ Load the dll associated with the CLSID after consulting the Registry</li>
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<li>
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Instantiate the class factory by calling a globally exported dll function
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<tt>NSGetFactory()</tt>.
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This
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returns an instance of the class factory that implements the <tt>nsIFactory</tt>
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This returns an instance of the class factory that implements the <tt>nsIFactory</tt>
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interface.</li>
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<li>
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@ -162,9 +149,65 @@ return <tt>false</tt>. XPCOM will not let the re-registration of the modified
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dll proceed in this case. There is nothing much that XPCOM library can
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do to salvage this situation other than warning the user of possible instability
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and advice a restart upon which the re-registration will happen.
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<h3>
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</h3>
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<h3>
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<a NAME="ProgID Spec"></a>ProgID Spec</h3>
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Let us consider some more examples:
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<ol>
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<li>
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A pluggable protocol that implementes the nfs protocol</li>
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<li>
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A converter that can handle application/x-zip</li>
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<li>
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A plugin that can handle image/gif</li>
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<li>
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A widget that can do a toolbar</li>
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<li>
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A datasource that can handle mail</li>
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<li>
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A helperapp that deals with application/postscript</li>
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</ol>
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All the above have what type they are and one or more arguments on what
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they particularly do.
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<p>The ProgID for these would look like
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<ol>
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<li>
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<tt>component://netscape/network-protocol&type=nfs</tt></li>
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<li>
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<tt>component://netscape/data-converter&type=application/x-zip</tt></li>
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<li>
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<tt>component://netscape/plugin&type=image/gif&name=ImageMedia's
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Gif Image Plugin&Description=Reders GIF Images....</tt></li>
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<li>
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<tt>component://netscape/widget&type=toolbar</tt></li>
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<li>
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<tt>component://netscape/rdf/datsource&type=mail</tt></li>
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<li>
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<tt>component://netscape/helperapp&type=application/postscript</tt></li>
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</ol>
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{Assume proper escaping of all above URI}
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<p>The above semantics would let ProgID be an extensible mechanism that
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could be searched on multiple ways. And
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<br>query on a progid should match only whatever was passed in. So a query
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for
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<br>component://netscape/plugin&type=image/gif should pass for the
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progid specified above. We could extend this
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<br>mechanism with wildcards, but I dont want to go there yet... :-)
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<br>
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<h3>
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How will all this help me</h3>
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<a NAME="How will all this help me"></a>How will all this help me</h3>
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For Component Developers:
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<ul>
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<li>
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@ -185,18 +228,78 @@ No more hacking in calls to <tt>nsIRepository::RegisterFactory()</tt></li>
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No need to know the CLSID of components that you want to instantiate. Component
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creation can happen like this</li>
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<br><tt>nsIRepository::CreateInstance(<b>"Gecko.LayoutEngine.1"</b>, NULL,
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domIID, &result);</tt>
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<br><tt>nsIRepository::CreateInstance(<b>"<font color="#CC0000">component://netscape/network-protocol&type=nfs</font>"</b>,
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NULL, domIID, &result);</tt>
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<br>instead of
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<br><tt>nsIRepository::CreateInstance(<b>RAPTOR_CLSID</b>, NULL, domIID,
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&result);</tt>
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<p>Another example : To create a button instance that supports IWidget
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interface,
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<br><tt>nsIRepository::CreateInstance(<b>"xpfe.button.1"</b>, NULL, nsWidgetIID,
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&result);</tt></blockquote>
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<br><strike>nsIRepository::CreateInstance(NFS_PROTOCOL_CID, NULL, domIID,
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&result);</strike></blockquote>
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<h3>
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Issues</h3>
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</h3>
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<h3>
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<a NAME="What has happened so far"></a>What has happened so far</h3>
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<ul>
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<li>
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Autoregistration implemented to grovel for components from the current
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directory</li>
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<li>
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nsRepository is a global object. Not nsIRepository exists.</li>
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<li>
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nsRepository::ProgIDToCLSID() implemented</li>
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</ul>
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<h3>
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</h3>
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<h3>
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<a NAME="Changes to XPCOM happening"></a>Changes to XPCOM happening</h3>
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<ul>
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<li>
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API changes to get ProgID in entire registration process for
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factories and components</li>
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<li>
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ProgID cache to improve performance of ProgID queries</li>
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</ul>
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<h3>
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</h3>
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<h3>
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<a NAME="What should I do"></a>What should I do</h3>
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<ul><b><font color="#CC0000">Component Developers</font></b>
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<ul>
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<li>
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<font color="#000000">Implement <tt>NSRegisterSelf()</tt> for your component
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dlls. Sample implementation that perf</font> <a href="http://cvs-mirror.mozilla.org/webtools/lxr/source/modules/libpref/src/nsPref.cpp#608">http://cvs-mirror.mozilla.org/webtools/lxr/source/modules/libpref/src/nsPref.cpp#608</a></li>
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<li>
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Use <tt>nsRepository::RegisterComponent()</tt> instead of <tt>nsRepository::RegisterFactory()</tt>
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if your component lives in a DLL</li>
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<li>
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<b>Dont use static constructors in loadable components</b></li>
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</ul>
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<p><br><b><font color="#CC0000">Component Users</font></b>
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<ul>
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<li>
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Create all your components using ProgID rather than CID</li>
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<li>
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If you were thinking of managing creation of components yourself, think
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again. The repository may be already doing that.</li>
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</ul>
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</ul>
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<h3>
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<a NAME="Issues"></a>Issues</h3>
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<ul>
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<li>
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@ -232,6 +335,9 @@ components to use.</li>
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<li>
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Is the hierarchy <tt>ROOTKEY_COMMON\\<b>Classes</b>\\CLSID </tt>acceptable.</li>
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<li>
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Should we have a nsIRepository</li>
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</ul>
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<hr WIDTH="100%">
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