Saturday, November 17, 2007

Session 16 - XPCOM lab - retry

I am on Linux an using Gedit to create the files for the XPCOM lab:

NOTE: Substitute $(objdir) for the path to your build directory

  • mozila/extensions/firstxpcom/public/IFirstXpcom.idl
  • Generate uuid through firebot for the .idl file -> 9de38b2d-6d9e-4350-bc8a-b5330de0accf
  • mozilla/extensions/firstxpcom/Makefile.in
  • mozilla/extensions/firstxpcom/public/Makefile.in
  • mozilla/extensions/firstxpcom/src/Makefile.in
  • mozilla/extensions/firstxpcom/install.rdf
  • Add ac_add_options --enable-extensions=default,firstxpcom to .mozconfig
  • $ cd $(objdir)
    $ ../build/autoconf/make-makefile extensions/firstxpcom //to do an incremental build and create the objects in the objdir
  • $ cd $(objdir)/extensions/firstxpcom
    $ make
  • This will create the public and src directories on the obj-dir, as well as generate the Makefiles necessary in each
  • $ cd $(objdir)/extensions/firstxpcom/public
    $ make

  • As a result of this first (partially) successful run of make, exported and generated header files (i.e.,from our IDL) will be placed in $(objdir)/dist/include/firstxpcom
  • Within $(objdir)/dist/include/firstxpcom/IFirstXpcom.h you'll see the following block of code:
    #if 0
    /* Use the code below as a template for the implementation class for this interface. */
    ...
    /* End of implementation class template. */
    #endif
  • Copy and paste this implementation stub into the following file: mozilla/extensions/firstxpcom/src/FirstXpcom.cpp
  • We also have to add the Module Code (read more ) at the bottom of the CPP file and #include "nsIGenericFactory.h" and in that code we will use these macros:
    • NS_GENERIC_FACTORY_CONSTRUCTOR(FirstXpcom)
    • NS_IMPL_NSGETMODULE(FirstXpcomModule, components)
  • $ cd $(objdir)/extensions/firstxpcom
    $ make
  • I had to change this statment for the next one:
    mName.Assign(L"FirstXpcom Component");
    mName.AssignLiteral("FirstXpcom Component");
    because I was getting this errors:
    ../../../../extensions/firstxpcom/src/FirstXpcom.cpp: In constructor ‘FirstXpcom::FirstXpcom()’:
    ../../../../extensions/firstxpcom/src/FirstXpcom.cpp:28: error: no matching function for call to ‘nsString_external::Assign(const wchar_t [21])’
    ../../../dist/include/xpcom/nsStringAPI.h:124: note: candidates are: void nsAString::Assign(const nsAString&)
    ../../../dist/include/xpcom/nsStringAPI.h:128: note: void nsAString::Assign(const PRUnichar*, PRUint32)
    ../../../dist/include/xpcom/nsStringAPI.h:132: note: void nsAString::Assign(PRUnichar)
    make[2]: *** [FirstXpcom.o] Error 1
  • Assuming this works without errors, here's what has happened:

    * Generated makefiles for your project were created in extensions/firstxpcom/ (remember, we're under /mozilla/$(MOZ_OBJDIR)/.
    * Exported header files and generated header files (from IDL) in dist/include/firstxpcom/
    * Static libraries for your modules in dist/lib/ (in case other modules want to link statically instead of using XPCOM).
    * XPI file in dist/xpi-stage/firstxpcom.xpi.
    * Everything else in dist/bin/extensions/firstxpcom@senecac.on.ca
  • I try to run the Firefox and see if it gets loaded and visible in the Addon Manager but I get this message:
    "Malformed File: Minefield could not install this item because "insall.rdf" (provided by the item) is not well-formed or does not exist. Please contact the author about this problem"
  • Ben Hearsum told me to try this: XML.com: RUWF? The XML syntax checker
    and the message I got was this:
    xml declaration not at start of external entity at line 1, column 1, byte 1:
    1.0" encoding="UTF-8"?>
    ^
  • I have been able to make, it seems to load BUT I can't see "FirstXpcom" as one of the extensions or add-ons
  • Anyway, let's continue and let's install the Extension Developer's Extension but it does not work on FF3, I have read in Rueen's blog post this:
    Problem: Can’t get the Extension Developer’s Extension to install on Firefox 3 due to extension security reasons.

    Answer: Install it in Firefox 2. Open Firefox 3. Type: about:config in the URL bar above. Right click on any Row and choose “new” then “boolean”. Now for name type: “extensions.checkUpdateSecurity” then click Ok. For value type: “false” and click Ok. Finally go to extension’s page and try to install it again. (Thanks Cesar)
  • You can skip to add to FF2, just add extensions.checkUpdateSecurity as false

  • After trying the rest of the lab I saw that I had to get the firstxpcom to be in the addons manager
  • After a while I realized that inside $(objdir)/dist/bin/extensions I had two folders I recognized "firstxpcom@senecac.on.ca" and "azambran@learn.senecac.on.ca", hehe, I know I have done something wrong
  • I went to the install.rdf and changed my email address to "firstxpcom@senecac.on.ca" since on the cpp I registered the component with "@senecac.on.ca/firstxpcom;1"
  • I delete both folders in the $(objdir)/dist/bin/extensions and $(objdir)/extensions/firstxpcom
  • $ cd $(objdir)
    $ ../build/autoconf/make-makefile extensions/firstxpcom
  • $ cd $(objdir)/extensions/firstxpcom
    $ make
  • run minefield and there we go! the firstpcom shows as one of the addons


  • Let's test the Java Script shell, Tools > Extension Developer > Javascript Shell
    • const cid = "@senecac.on.ca/firstxpcom;1"
      var obj = Components.classes[cid].createInstance()
      obj = obj.QueryInterface(Components.interfaces.IFirstXpcom) //We are QI it to IFirstXpcom...
      var sum
      sum = obj.add(4,5)
      obj.name = name
      print(obj.name)
      alert(obj.name)
Awesome, my first XPCOM component!!!

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