Hacking

My first hack

So - we've built and run OO.o, and we want to prove to ourselves that it is in fact possible to hack on it. So in a new terminal do this:

cd build/src680-m66
. ./LinuxX86Env.Set.sh
cd vcl

Now have a hack at vcl/source/window/menu.cxx (Menu::SetItemText); (near line 1770) I suggest manually applying this change:

-               pData->aText = rStr;
+               pData->aText = String(rStr).Reverse();

Then save. ( You can find more sensible things to hack in the Tutorials )

You're still in vcl/ yes ? then type 'build debug=true'; wait for the scrolling text to stop; (5 seconds?). Now re-run soffice -writer. You should notice the effect in the menus. If not, ensure the previous soffice.bin was dead with killall -9 soffice.bin

Note: for day to day hacking you want to just run 'build' inside the source tree. It is also highly recommended to work inside a copy of the build tree, and generate / test patches in an un-hacked version. To copy just the build/src680-m66 directory elsewhere, you need to use the relocate tool.

Read the Fine manual

With the power of C++ comes the ability to shoot yourself in the foot all the more easily; (and implicitly), cf. Holub, Rules for C and C++ programming, McGraw-Hill, 95.

The best way to prepare yourself for battle is to read the OpenOffice coding guidelines, and for the easily confused c'tor / d'tor is short for constructor / destructor.

Also, there's an extensive list of recommended literature about C++ - but that's of course no prerequisite to start coding.

Sending patches

The toplevel structure of the OO.o source code is not the same as the layout of the CVS repository [ a good rational for this strange state of affairs is absent ]. Thus to work out what real module a file is in you need to do eg.

       cd binfilter
       cat CVS/Repository
       framework/binfilter

This shows you that the 'binfilter' directory is part of the 'framework' project.

These days there is a hackers bug filing page that will assign bugs to the correct project, and the correct owner to get rapid attention.

Starting the right app

As you start soffice.bin, there are several useful parameters to use to accelerate your debugging experience; particularly -writer, -calc, -draw, and (the wizardly painful) -impress arguments.

Understanding D' make (man)

While the build system is in similar to many other systems, it is also perhaps slightly different. The overview is that each module is built, and then the results are delivered into the solver. Each module builds against the headers in the solver. Thus there are a few intricacies.

• build — this perl script solenv/bin/build.pl is used in conjunction with prj/build.lst to ensure that every module that is needed is built first.
  build then un-winds internal module dependencies, and builds each module with a chdir, dmake pair.
• deliver — this perl script solenv/bin/deliver.pl installs headers, and libraries (etc.) into the solver, as informed by prj/d.lst. Crucially deliver ensures that the date stamp on any file that is installed to the solver is the same as that in the module's directory. This ensures, that (particularly for headers) that there is no dependency cascade triggering re-builds in other modules.

Standard directories

There are various standard directories and files in most of the modules that make up OO.o, here are some of the more useful:

• prj
  • build.lst — this lists directories to be made, '^#' comments are allowed, the order of the list is immaterial see detail, it is dictates build's operation.
  • d.lst — this file describes the deliver process, see detail.
• util — typically the util directory is charged with glueing together the sub-libraries for each sub-module into a single large library, adding system library dependencies, building GUI resource files etc. All the work is described in makefile.mk, this is usually the last directory to be built in a project.
• inc — public headers are typically separated into an 'inc' directory, these will be installed into the solver by the 'deliver' phase (using prj/d.lst)

Build's mode of operation is to invoke 'dmake' in each of the projects' directories with a given dependency order. dmake then executes the rules in makefile.mk.

prj/build.lst

On first view build.lst looks scary:

vc      vcl : NAS:nas FREETYPE:freetype psprint rsc sot ucbhelper unotools sysui NULL
vc      vcl                      usr1   -       all     vc_mkout NULL
vc      vcl\source\unotypes      nmake  -       all     vc_unot NULL
vc      vcl\source\glyphs        nmake  -       all     vc_glyphs vc_unot NULL
...
vc	vcl\mac\source\src	 nmake	-	m	vc__srcm vc_unot NULL
vc	vcl\util		 nmake	-	all	
vc_util vc__plug.u vc__appa.u vc__appm.m vc__appu.u vc__appw.w vc__gdim.m 
vc__gdiu.u vc__gdiw.w vc__srcm.m vc__srcu.u vc__srcw.w 
vc__wina.u vc__winm.m vc__winu.u vc__winw.w vc__du.u 
vc__gtka.u vc__gtkw.u vc__gtkg.u vc__kde.u vc_app 
vc_ctrl vc_gdi vc_hlp vc_src vc_win vc_glyphs NULL
      

so we need to try and un-pack what's going on here, which is in fact not as odd as it might seem at first glance. Firstly lists are terminated by the 'NULL' string. Every line is prefixed by a module shortcut which has to be unique, no two modules are allowed to have the same shortcut.

• First active line contains a ':', this describes the fact that this project (vcl) depends on these other modules 'nas', 'freetype', 'psprint' etc. to be built first. This is for inter-project dependencies.
• Some modules have a CAPITALS:lowercase arrangement; the first segment is a conditional, driven by a space delimited list in the BUILD_TYPE environment variable at build time.
• Then we have a redundant line 'usr1' [ for fun ? ], in fact only lines containing the magic string 'nmake' are valid after this.
• The next lines describe internal project directory dependencies and look like:

  [shortcut] [path to dir to build] nmake - [flags] [unique-name] [deps...] NULL
  vc           vcl\source\glyphs    nmake -   all     vc_glyphs   vc_unot   NULL
  	     

  shortcut can be used to differ between modules.
  flags determines which platforms this directory builds on; usually either 'all' or single char platform codes: 'uw' 'u' being Unix, 'w' Windows. The higher up the system, the more stuff is flagged 'all'.
  unique-name this is a magic name, used by other lines to describe an internal dependency.
  deps... any number of names of other directories in this file, that must be built before this one. If such prerequisite dir is built for special platforms only, the platform code has to be appended to its magic name.

So we see in the vcl case that vcl\source\unotypes (vc_unot) has to be built before vcl\source\glyphs (vc_glyphs). For Mac vcl\mac\source\src (vc__srcm) has to be built before vcl\util (vc_util) It is important to understand that the order of the list is ~immaterial, and instead of a simple ordered list, we have a more complex internal dependency system — this contrasts with most other make systems.

There is also documentation here on it.

deliver, deliver.log and prj/d.lst

The syntax of d.lst is more comprehensible than build.lst, it omits some default actions, such as copying build.lst into

inc/<module>/build.lst.

A line is of the form:

       [action]: [arguments]
       mkdir:    %_DEST%\inc%_EXT%\external

where if '[action]:' is omitted, it defaults to the 'copy' action. Typical actions are copy, mkdir, touch, hedabu, dos and linklib.

The 'hedabu' action is particularly interesting, inasmuch that it cosmetically re-formats the header to shrink it on install and adds the module name to the include path (#include "my_header.hxx" becomes #include <my_module/my_header.hxx>). Otherwise it's much like the copy action.

     During the action, various macro variables are expanded some of which are:

• %__SRC% — distribution directory name eg. unxlngi4.pro
• %_DEST% — absolute path into solver eg. /opt/OpenOffice/OOO_STABLE_1/solver/641/unxlngi4.pro
• %_EXT% — (unusual) way of having minor updates eg. 641.1, typically used to version every base sub-directory.

Typically then, if indeed you need to add a rule (cf. implicit directory copies), it will be of the form:

       ..\%__SRC%\inc\sal\*.h %_DEST%\inc%_EXT%\sal\*.h

NB. relative paths are relative to the 'prj/' directory.

Sometimes you might run into the situation where you'd like to remove the delivered files from solver. Your configuration might have changed and they are no longer needed. "deliver -delete" does just that, however you might still need to delete "deliver.log" files manually as well.

Can I get a char *, please?

Just barely. OO.o has at least six string wrappers, although the C implementations are of little interest:

• rtl_String — sal/inc/rtl/string.h
  "Normal" string plus reference counting. rtlstring->buffer is useful, as is rtlstring->length. This object encapsulates an generic 8bit string - of unknown encoding. Feel free to treat rtlstring->buffer as your beloved char *. If you really want to look at the implementation of some rtl_String function and lxr nor grep can help you, have a look at sal/rtl/source/strtmpl.c.

• OString — sal/inc/rtl/string.hxx
  Simply a rtl_String wrapped inside a class; you can use ostring.pData to get at the rtl_String (it's public). OString has reasonably useful methods for if you need them.

• rtl_uString — sal/inc/rtl/ustring.h
  "Normal" Unicode string, similar to rtl_String, and refcounted as well. However, this one always comes in UCS-2 encoding, presumably to be compatible with Java's questionable choices. See rtl_String above to find where the implementation of some rtl_uStringfunctions is hidden.

• OUString — sal/inc/rtl/ustring.hxx
  An rtl_uString wrapped inside a class. This is what most of the OO.o code uses to pass strings around. To convert an OString to an OUString it is necessary to specify the character set of the OString see; sal/inc/rtl/textenc.h — the only interesting case is RTL_TEXTENCODING_UTF8

• String — tools/inc/string.hxx
  This is an obsolete string class, aliased to 'UniString'. It has a number of limitations such as a 64k length limit. You can have the buffer with GetBuffer(), but it's Utf-16 encoded.

A couple of conversion functions are really useful here, particularly:
rtl::OString aOString = ::rtl::OUStringToOString (aOUString, RTL_TEXTENCODING_UTF8);
And the reverse:
rtl::OUString aOUString = ::rtl::OStringToOUString (aOString, RTL_TEXTENCODING_UTF8);

If you just want to programattically print out a string for debugging purposes you probably want define a macro like :
#define CHAR_POINTER(THE_OUSTRING) ::rtl::OUStringToOString (THE_OUSTRING, RTL_TEXTENCODING_UTF8).pData->buffer
and use it like :
printf ( "SvXMLNamespaceMap::AddIfKnown : %s / %s\n", CHAR_POINTER(rPrefix), CHAR_POINTER(rName) );.
For the obsolete String class, aliased UniString, it's like :
printf ( "rGrfName : %s\n", ByteString( rGrfName, RTL_TEXTENCODING_UTF8).GetBuffer() );

To print the value of rtl::OUString directly in the debugger, you can use dbg_dump(). It is intended to be called interactively from the debugger, in both debug and non-debug builds of OOo. You can see the definition in sal/rtl/source/debugprint.cxx.

Some code snippets about manipulating those objects can be found on the codesnippets service page : [1]

Linkoo & Limitations

Linkoo is the tool that implements the -l functionality of bin/ooinstall. It essentially sym-links files of similar names into your local tree, allowing a fast development iteration.

It is however slightly limited - some of the modules cannot be linked for various reasons; these are: cppuhelper and configmgr, thus in the rare case that these are altered, they must be copied manually into /opt/OOInstall/program.

In addition symlinks cannot be used for soffice.bin, and this is more commonly altered - it has to be installed from desktop/unxlngi4.pro/bin/soffice NB. with an appended '.bin'

See also

• Debugging
• Using C++ with OOoSDK