Inkscape Wiki - User contributions [en]

Working with Bazaar

2010-08-20T11:34:46Z

Bkor: Upload the public key, not the private one!

==Bazaar concepts==

It is assumed that you are familiar with the basic concepts of version control, like working copy, committing, updating, conflicts. There will be a section that explains the basic functionality soon.

; '''Branch'''
: is a working copy of the project's code. Typically you use one branch per set of related changes, for example a new output extension. Once your work is finished, you ''merge'' your branch into a larger project. Initially, there is only one branch, the trunk; all other branches are its (probably indirect) descendants. To create a new branch, you have to copy an existing one.
; '''Checkout'''
: is a copy of code contained in a branch that is not stored on your computer (a remote branch). Committing to a checkout will immediately apply the changes to the remote branch. Commits will not succeed if somebody else modified the branch while you were working - you need to have an up-to-date working copy - or when you're offline.
:When branches A and B have a common ancestor branch but each contain changes not present in the other, they have '''diverged'''. For example, when you work on an improved rectangle tool in your own branch and at the same time somebody else applies a PDF export bugfix to the trunk, your rectangle tool branch becomes diverged from the trunk.
; '''Trunk'''
: is the main branch, which represents cutting-edge working code. You should start from it when doing any new development.
; '''Merge'''
: is the process of reconciling changes made between two branches since they diverged. This operation is asymmetric. When you merge A into B, all changes made to A since it was branched from B are applied to B. A is not changed. When you work on some feature, you typically work in a branch, periodically merging the trunk into your branch (to sync up with the latest changes), then you merge your work into the trunk. Merging is similar to applying a patch - it only changes your working copy. To apply a merge, you need to commit the changes it introduced. Merging un-diverges branches.
; '''Repository'''
: is a place where branches of a project are stored. Having a shared repository reduces the storage requirements of multiple branches of one project. Instead of O(number of branches) space, the Bazaar data takes up O(total size of changes in all branches) space.
; '''Bind'''
: is the process of converting a non-diverged local branch into a checkout of the remote branch.
; '''Push'''
: is the process of publishing an exact copy (a mirror) of your branch in some other location. The difference between pushing and checkouts is that a checked out remote branch is updated every time you commit, while a pushed remote branch is updated only when you push to it - you can commit any amount of changes between pushes. You can only push to a branch if the mirror has not diverged from your local copy. This can happen if more than 1 person can push to the same location.
; '''Pull'''
: is the process of creating a local exact copy (mirror) of a branch, in principle a reverse of pushing.

==First steps==

First you need to tell Bazaar your name. This will appear on all your commits. You should use your real e-mail, but you can obfuscate it if you are afraid of spam.

Obfuscated e-mail examples:
$ bzr whoami "John Q. Public <john dot q dot public at-sign bigmail dot com>"
$ bzr whoami "John Q. Public <removethis.john.q.public@bigmail.com>"
Unobfuscated e-mail example:
$ bzr whoami "John Q. Public <john.q.public@bigmail.com>"

If you have an account on launchpad and want to commit changes there, you need to specify your launchpad login:
$ bzr launchpad-login johnq

Then fetch Inkscape's trunk
$ bzr branch lp:inkscape

To carry out a later update of Inkscape's trunk
$ bzr pull lp:inkscape

==Using a centralized (SVN-like) workflow==

In this case, every commit that you make is immediately sent to the central repository. There are two ways of achieving this:

===SVN-style checkout===

Get the latest Inkscape code as a checkout, rather than a branch:
$ bzr checkout lp:inkscape

Now work as in SVN:
<do work>
$ bzr commit
<error, someone else has changed things>
$ bzr update
<check all is okay>
$ bzr commit

If you add new files, add them to version control with <tt>bzr add ''file''</tt>. You can recursively add all new files by writing simply <tt>bzr add</tt> in the top level directory.

===Binding a BZR branch===

Get Inkscape's code the regular bzr way:
$ bzr branch lp:inkscape

Then transform your banch into a checkout:
$ cd inkscape
$ bzr bind lp:inkscape

Now work as in SVN:
<do work>
$ bzr commit
<error, someone else has changed things>
$ bzr update
<check all is okay>
$ bzr commit

===Differences from SVN===

* Commits will fail if your checkout is not up to date, even if there would be no conflicts.
* The revision number is an attribute of the working tree, not of individual files. It is not possible to have different portions of the working tree at different revisions.
* <tt>bzr commit ''file''</tt> works like <tt> svn commit ''file'' && svn update ''project-root''</tt>. After a successful partial commit, the entire tree's revision is increased by 1.
* No special server is needed to publish a branch. You can push branches to anywhere, including simple FTP shares. In our scenario, Launchpad works like a central repository, but it's not required to publish everything there.
* You create branches locally. To simulate creating a SVN-style branch on Launchpad, you need to create a local branch, push it, then bind it to the pushed location.


==Using a decentralized workflow==

In this case you will be working locally until you are ready to publish your changes. The basic idea is to perform the work in a ''branch'' of the Inkscape repository, since committing to a branch stores the changes locally in the branch itself. Then, to share the work with the rest of the Inkscape community, the changes in the branch are merged across to a ''checkout'' of the Inkscape repository. As the previous centralized workflow section describes, committing to a checkout sends the changes directly to the remote repository, making them part of the official Inkscape codebase.

'''NOTE:''' this workflow has been updated to avoid the "other people's commits become subrevisions of your commit" problem.

This will assume this directory layout:
inkscape
+-trunk
| +-doc
| +-share
| +-src
| +-po
| +-...
+-myproject
+-some-other-branch

In this layout, "trunk" is the checkout used for uploading changes to the central Inkscape repository, while "myproject" and "some-other-branch" are local branches used for working on specific features.

===Repository setup===

To speed things up, it's good to create a local shared repository. This way revision histories will only be stored in one place, instead of in every branch, so local branching will be faster and the branches will take up less space.

Create a shared repository and enter it:
$ bzr init-repo --rich-root inkscape
$ cd inkscape

===Working locally===

Get Inkscape's code
$ bzr branch lp:inkscape myproject

Now work:
$ cd myproject
... work work work ...
$ bzr commit -m "Some changes"
... more work work work ...
$ bzr commit -m "More changes"
... create new file ...
$ bzr add new-file.c
$ bzr commit -m "Added new file with kittens"

===Advanced local features===

To undo a commit:
$ bzr uncommit
This will leave your working tree in the state it was just before you wrote "bzr commit". This is useful for example if you forgot to add a file, and want to keep a clean revision history. This will NOT work on a trunk checkout.

Let's say you started from r770 200 local commits, but you decided that what you did since r954 is completely wrong. You want to go back to revision 825 and do it differently. Here's one way to do this. First branch locally to preserve your work (maybe later you'll find out there's some way to save it). Then uncommit everything up to r954 and revert.
$ bzr branch myproject myproject-dead-end
$ cd myproject
$ bzr uncommit -r 954
$ bzr revert

A different scenario: let's say that commit 1524 introduced a bug, but there were 50 other commits since then and you only want to revert the changes introduced by 1524.
$ bzr merge -r1524..1523

Sometimes a big change gets committed while you are working on a feature. If you want to check whether your code still works after the big change, merge from trunk.
$ bzr merge

In this case, you can omit where you are merging from, because the default is to merge from the branch you started from (the parent).

===Publishing your work on Launchpad===

To publish branches on Launchpad, you have to add an SSH key to your account. If you don't have one yet, generate it:
$ ssh-keygen
... follow instructions ...

Once you created the key, go to your Launchpad profile page, edit SSH keys and paste the contents of the key file (by default it's in <tt>~/.ssh/id_rsa.pub</tt> or <tt>~/.ssh/id_dsa.pub</tt>) into the window. You can now use the Launchpad integration features.

Login to Launchpad, if you didn't do it yet. You only need to do this once on each computer. You need to use your login name, not the display name.
$ bzr launchpad-login johnq

Publish your branch on Launchpad.
$ bzr push lp:~johnq/inkscape/myproject

The push location will be saved. After more commits, you can simply write
$ bzr push

It's sometimes convenient to update the Launchpad copy after each commit. To save on typing, you can bind your working tree to the remote branch. This way every commit will be immediately published on the remote branch. Note that you won't be able to commit while offline.
$ bzr bind :push

===Putting your work in the trunk===

Once your new killer feature is ready, you need to merge your changes into a checkout of the trunk. If you don't have one, do (in the directory ''containing'' myproject):
$ bzr checkout lp:inkscape trunk
$ cd trunk

If you already have one on hand, make sure it's up to date:
$ cd trunk
$ bzr update

Now that you have a local checkout of the current trunk:
$ bzr merge ../myproject
$ bzr commit -m'added my feature'

WARNING: There is an alternative method that consists of merging trunk into your local branch, then pushing the result as trunk. Do not do this! It obfuscates the revision history.

===Working with patch files===

If you don't have permission to commit to the trunk, you can bundle your branch's changes into a patch instead:
$ bzr send -o mychanges.patch

To apply patches produced by the above command, just do this:
$ bzr merge somechanges.patch

===Local branching===

Naturally, all this also works locally. For example, when you're in the <tt>inkscape</tt> directory, you can write <tt>bzr branch trunk export-dialog</tt> to create a new branch of the trunk called <tt>export-dialog</tt>, where you'll work only on improving the export dialog. Similarly, you can merge between local branches.

==Best Practices for Inkscape Project==

===Registering Bugfixes===

Launchpad will automatically mark a bug "Fix Available" (rather than "Fix Committed") once somebody commits using the flag --fixes, e.g. (if you fix those two bugs in one commit):
bzr commit --fixes lp:123456 --fixes lp:123457 -m 'patch description'
Then, bugs can be changed automatically from "Fix Available" to "Fix Released"

[http://doc.bazaar-vcs.org/bzr.dev/en/tutorials/using_bazaar_with_launchpad.html#changing-the-state-in-launchpad-while-committing-in-bazaar Read more: "Changing the state in Launchpad while committing in Bazaar"]

===Proper way of merging===

To repeat, NEVER do something like:
$ bzr branch lp:inkscape myproject
... work ...
$ bzr commit
$ bzr merge # NOOOO!!! We are doomed!
$ bzr push lp:inkscape

It will obfuscate the revision history: trunk commits that happened between the time you branched and the time you pushed will get grouped into one. Do the merge the other way around:
$ bzr branch lp:inkscape myproject
$ cd myproject
... work ...
$ bzr commit
$ cd ../trunk
$ bzr merge ../myproject # correct!
$ bzr commit

You'll need a trunk checkout, but the revision history will be much less confusing, and it's useful to have a trunk checkout anyway.

==External links==
* [http://doc.bazaar-vcs.org/latest/en/ Bazaar manual]

Script extensions

2010-08-19T12:10:30Z

Bkor: Fix extensions location

[Note: This page concerns using scripting languages to create new Inkscape functionality. To access Inkscape functionality from scripting languages (i.e. to script Inkscape), see the Inkscape man page (especially in the development version or v0.46 or later, which provide --select and --verb options), or see the work in the src/extension/script directory of Inkscape source.]

=== Introduction ===

Traditional unix scripts can be used to extend Inkscape's functionality.
Such programs read a stream of data on standard input, transform the data in some way, and then write the modified data to standard output. This is an easy way to expand Inkscape and provide custom functionality without learning the internals of Inkscape. Libraries for reading and writing SVG data exist for many programming languages, and most provide support for XML. This HOWTO describes the "ins and outs" of writing one of these scripts and making it work with Inkscape's core functionality.

=== Types of scripts ===

There are three kinds of functions that can be added with a script:

* Input, providing translation from a file format to SVG
* Output, providing translation from SVG to a format
* Effect, taking in SVG, changing it, and then outputing SVG

While all of these are very similar in the scripting interface, there are slight differences between them.

=== Interaction ===

It is important for a script author to understand how Inkscape and scripts communicate.

(interpreter)? your_script (--param=value)* /path/to/input[[/SVGfile]] | inkscape

Inkscape runs your script (optionally with an interpreter) passing it any number of parameters in long gnu style. The final argument is the name of the temporary svg file your script should read. After processing, the script should return the modified svg file to inkscape on STDOUT.

=== Important Tips ===

* Receive the inkscape arguments.
* Clear temp files if it creates one.
* Write full changed SVG to the default output.
* Don't break an xml:space="preserve" area.
* Send error text to the error output and help the user.

=== Description ===

In order for Inkscape to make use of an external script or program, you must describe that script to inkscape using an INX file. See the inkscape share directory for examples. The INX file allows the author to:
* label strings for translation
* define parameters
* chain extensions
Please see [[MakingAnINX]] for help creating an INX file for your script.

==== Parameters ====
The INX file describes which parameters the extension needs. Inkscape will prompt the user with a UI to fill out these parameters before the extension is called. Each parameter will be passed through the commandline as "--paramname=paramvalue". Eg. if you have described a string parameter with name 'string1' in the INX file, Inkscape will present a textbox to the user. When the user fills in "text" and presses OK, it will pass '--string1="text"' to the program specified by the <command> tag.

There are several types of parameters that can be requested by the INX description:

* Boolean
* Int
* Float
* String
* Description
* Enum
* Notebook
* Option group (radio buttons)

=== Installing ===

Installing is as simple as copying the script (unless it resides in your path) and its INX file to the inkscape/share/extensions ($HOME/.config/inkscape/extensions) directory. (If you install a script in your home directory be sure to copy the dependencies.)

If you are looking to use scripts that have already been written, the most difficult part will likely be the installation. Since scripts are separate programs they may have any number of dependencies that are not included with inkscape. Currently, the best way to find missing dependencies is by reading the error messages produced by running the script from the command line.

=== See Also ===

*[[Generating_objects_from_extensions]]. How to use a script to generate actual objects inside SVG documents.

*[http://www.ekips.org/comp/inkscape/extending.php#ignorance| Aarons website] describing his path to learning how scripting extensions work. '''VERY OUT-OF-DATE'''

*[[MakingAnINX]]

*[[PythonEffectTutorial]]

*[[Tips For Python Script Extensions]]

[[Category:Extensions]]

Developer manual

2010-08-18T19:34:02Z

Bkor: update developer.gnome.org to library.gnome.org

= Inkscape Developer's Manual =

== Introduction ==

For those of you just joining us, or who have been with us but are just
now getting the itch to work on Inkscape, I thought I'd give some tips
for how to get started working in the codebase based on our own
experiences.

One of the first things most people wonder is "what should I work on".
As you may have already noticed, we generally don't "assign" projects.
We figure there's plenty more work to do than people to do it, so you
may as well work on something that you're either interested in or that
adds something of benefit to you; that's extra motivation to get your
own itches scratched.

If you're really stumped though, we keep a detailed [[Roadmap]] in wiki that
you're welcome to browse through to look for ideas of things to work
on. Tasks that do not have names beside them are open for anyone to
take; if you want to take ownership of a task, just put your name beside
it. Feel free to add or reword tasks as needed, although try not to
load up the current milestone with tasks that aren't critical for the
release. Feel free to work on stuff that is several milestones down the
road; there's rarely any problem with getting stuff done sooner than
planned. ;-)

We have a process for gaining SVN commit access. The reason is that
while it is important that we keep access to the codebase open, we don't
want to be crazy and leave it wide open to any random passer-by. The
process is that we require that the person make two contributions
(patches, documentation, web collateral, etc.) and then make a request
to get account access.

In general you won't need SVN commit access in order to start doing
development, because you can work from an anonymous checkout and create
patches. If you've not done this before, you'll need to learn this
skill first (basically see docs for `svn diff`).

When you first start hacking on Inkscape code, I wouldn't recommend
taking an objective of implementing a specific feature, because you will
need some time to familiarize yourself with the codebase, and because
you won't really know what features are going to be straightforward to
implement and which will be highly challenging. Of course, if you have
the time and love adventures, this might be a fun way to go.

There are four approaches that I've seen people effectively use in
getting into the codebase:

<ul>
<li>Write code documentation. Some people who don't mind adding
comments to code or writing docs find it useful to just go through
code they're interested in working on and writing up what it does.
The codebase is in dire need of better docs, so this approach pays
dividends well into the future.
</li>

<li>Fix bugs. Tracing down the cause of reported bugs is an effective
way to gain understanding of the codebase in small chunks. Many
common bugs can be traced down and fixed in a matter of hours, and
often will identify some bit of code in need of refactoring or
extension. Note that some of our older bugs are in the system
because they're hard to fix, so you'll want to work on the more
recent ones.
</li>

<li>Chip in on a group effort. Occasionally we identify a major
refactoring effort (such as when we converted from C to C++), that
we encourage lots of people to help on, in the philosophy that many
hands makes short work. This work tends to be pretty rote so is
not hard for new folks to get involved with; it just takes time. We
generally have one of these kinds of efforts per release. It
usually isn't glamorous work, but in aggregate moves the codebase
forward in a major way.
</li>

<li>Subsystem/module work. Some people want to get their hands in the
details quick, so take the approach of developing new code separate
from the codebase, to be integrated in later. This generally tends
to take a larger time commitment than the other approaches, but can be
an effective approach in some circumstances. We have a SVN module
called 'experimental' that you're welcome to house your work until
it's ready for prime time.
</li>
</ul>

Beyond that, you're going to find the documentation for the Inkscape
code is pretty scarce. We've worked on bits and pieces but
unfortunately the vast majority of the code is undocumented. On the
plus side, often you can implement the stuff you care about after
learning only a limited portion of the codebase.

I think you'd find Inkscape an enjoyable Open Source project to work on.
There's a huge range of interesting and useful skills that can be
learned from it, plus the developers are great guys to participate with.
The project itself runs smoothly and puts a premium on keeping things
friendly and low-stress, so heated arguments are rare. The users have
been great to work with and very appreciative of even small new features
and fixes. Plus, since Inkscape is so visual in nature, it's very cool
to see how your little changes make noticeable improvements to the app
overall.

== C++ Reference ==
* FAQ (with answers) sheet. We strongly recommend that everyone read this site comprehensively. You should not need to bookmark it, it should be the first of the sites on your autocomplete list for <code>par</code>!

http://www.parashift.com/c++-faq-lite/

It is actually more in-depth than the name FAQ suggests. Many experienced C++ programmers would benefit from it.

* List of [http://www.cs.helsinki.fi/u/vkarvone/2004s/cplusplus/errors.html schoolboy errors]. None of these should appear in [http://en.wikipedia.org/wiki/Free/Libre/Open-Source_Software FLOSS] code.

== Strings ==
Please make sure any user-visible strings are localizable. This requires wrapping them with "_(" and ")", like so:

"Select object"
becomes
_("Select object")

In case the interpretation of the string may be ambiguous or may differ according to context, you can add a context prefix (that won't be displayed) in order to eliminate the ambiguity.
"Ambiguous string"
can then become
Q_("Context|Ambiguous string")

For more complex things, please check the gettext/localization documentation.
See also http://library.gnome.org/devel/glib/unstable/glib-I18N.html

== Implementing User Interface Changes ==

[[UI improvements]] are enjoyable to work on because they produce visible changes in how Inkscape works. These improvements are one of the most tangible ways to help improve how Inkscape works; thus, we strongly support new developers wishing to work in these areas.

It is also very important to us that Inkscape presents an organized, productive, and easily discoverable interface to users, and because of this it is important that new Inkscape UI developers work to ensure changes make Inkscape's UI *more* consistent, *more* flexible, *more* cohesive, and so on. We don't have firm rules about what can and cannot done, so as to ensure there is plenty of freedom for innovation. However, we can outline some general principles and guidelines that are important to keep in mind:

'''Don't please the artist - BE the artist''' - Many times UI is designed and created by programmers who "understand what the user wants". But in Inkscape we believe that the best requirements list is the list inside the user's head. Requirements docs, usability studies, and so on are very indirect ways of transferring this gut-level understanding from user to programmer. We believe the best way to ensure this information is communicated clearly is for the user to BE the programmer. Or, alternatively, for the programmer to BECOME a user.

This is why we so strongly encourage users to get involved in coding, and why we so strongly encourage programmers to focus on the features that are most important to them personally. This is also why it is absolutely critical to pay close attention to what users report when using a new feature - often they can tip you off to alternate designs that achieve the same result in a better way.

'''Eliminate limitations''' - Commercial software is often developed to fulfill feature requirement lists from a marketing department. As such, it's common to see the feature implemented to meet the requirement exactly, and no more. However, especially with artistic software, art is often found outside what seems reasonable. So when putting in a new feature, avoid the temptation to limit it to what you expect people to use it for - instead generalize it and open as many parameters as possible for tweaking, and let the artist decide what is reasonable - that is their job.

As an example, a drawing program might want to support the features, feather and drop shadow. Obviously, users need these important features. Commercial software may well implement these as distinct features, each with their own UI controls. However, these features are just special cases of the more general gaussian blur, and in Inkscape we implemented *that*. With that in place, artists can not only do feathering and blur, but a whole variety of other effects.

It is interesting to note that, as an open collaborative standard, SVG
necessarily has the same goals as Inkscape: a minimum set of
universal, well thought-out building blocks that can accommodate the
widest possible range of graphics and applications. Thus, simply by
following the SVG philosophy, Inkscape scores quite a few important
points over commercial software. Live clones, patterns that can be contain any
objects, layers that are essentially groups and can be easily
converted to/from groups - all these are examples where the underlying
universality of SVG directly translates into extremely valuable user
features.

== Implementing New SVG Features ==

The most important way to help Inkscape is to implement a new SVG feature in it. Our hope is to eventually support ALL SVG features, so if you can help check one off the list, it brings us close to the nirvana of 100% SVG compliance. :-)

Generally we find that implementation of an SVG feature goes through three discrete stages:

1. Find the appropriate tags and attributes in the SVG spec
2. Implement support for rendering files with these tags
3. Implement support for UI controls to edit the tags

(1) is mostly a research project. Start by reading the SVG spec so you
can learn about the tag, the attributes that go with it, and so forth.
It is good practice to set up a page in the Wiki for storing your notes
as you do this process, so that in case you don't make it to steps 2 and
3, then maybe someone else can benefit from your research.

(2) is the fun part. It helps to be comfortable with Inkscape internals
for this part. Depending on the feature, it may require advanced
knowledge of transformation, rendering, document management, and so on.
For this part, just hand-edit an SVG file to put the tags in that you
found in step #1, and keep plugging away at the code until Inkscape
displays things as the specification dictates. It can help to compare
your work with Batik, as we use that program as our reference
implementation.

(3) is the most important stage, since it is the point at which the
feature becomes available for users. This step often requires knowledge
of Gtk+, for creating dialogs, widgets, menus, etc. for allowing the
user to edit the characteristics of the feature. Be sure to listen to
feedback from other developers and users - especially if there are
different opinions. It is hard to come up with UI that everyone can
agree on, but it is worth the work to achieve this - the more critique
your UI survives, the better loved the feature will be for future users.

Looking through Inkscape's history, these stages are often done by different people. If you're new to Inkscape, you may find working on stages 1 and 3 easiest, but there are many developers who can answer questions when you're ready to dig into the internals, so don't be afraid to ask questions!

== Standards Compliance - Extension Namespaces ==

* Only elements and attributes from our extension namespaces that ''do not affect rendering'' may be saved in SVG documents.
* Generally, this means that extension elements and attributes should only be used to provide UI hints.
* Extension elements and attributes should ''only'' be used where an existing facility provided by XML or SVG is not sufficient.

== Global Verbs ==

Here's a readers' digest summary of how Inkscape accelerators work:

A global mapping between key combinations and integer verb IDs
(sp_verb_t) is maintained in shortcuts.cpp; these are registered using
sp_shortcut_set().

Given an sp_verb_t and an SPView, you can get an SPAction which
represents that action in that view. These mappings are currently
hard-coded in verbs.cpp.

SPActions derive from NRActiveObject, which putatively provides a
"lightweight" method of doing callbacks, versus GObject signals. I
don't completely understand how it works.

SPActions also contain the label, image, etc, used for buttons and
menuitems.

sp_shortcut_invoke() looks up the SPAction for a keypress and SPView and
invokes it automatically. SPEventContexts call it for keypresses that
they do not handle themselves.

== Garbage collection ==

As you know, many automatic garbage collectors (like libgc) only
free and recycle memory periodically. This means you may have some
extra slush that could be freed, but hasn't yet.

There are other forces at work, though...

Pretty much all allocators, whether automatic or not, whether the
system malloc() or some custom allocator like libgc's, work the
same way: they request large blocks of memory from the operating
system, then divvy those blocks into smaller ones internally to
satisfy application allocation requests.

When an application frees memory, that memory is usually recycled
internally rather than returned to the OS immediately. The reason
for this is that the large memory blocks acquired from the OS must
be completely unused before they can actually be freed.

Let's say for example that an allocator acquires 16 8MB blocks from
the OS in response to 32768 4k application allocations...

In a worst-case scenario, it's possible that the application could
free 32752 of those 4k blocks but the remaining 16 4k just happen
to be distributed across the 16 8MB blocks requested from the OS.

If that happens, from the application's point of view it may only
have 64k allocated, but as far as the OS is concerned, it's still
using 128MB!

Note that this applies to nearly all allocators in common use.

While it's unusual for things to get quite that bad, memory
fragmentation is common enough that many popular allocators (for
example Perl's) simply don't bother trying to return memory to the
OS at all (the memory will still get forcibly reclaimed by the OS
when the process exits).

[ FWIW, libgc's allocator is one of the ones that _does_ make an
effort to release memory to the OS, but it is limited by
fragmentation like any other ]

Also note that for various reasons, the statistics you get from the
OS aren't going to directly reflect the amount of heap-allocated
memory. Be careful drawing conclusions from only looking at e.g.
the output of top(1)...

(the worst thing is that due to the modern practice of
overcommitting memory, the OS may literally lie to an application
about the amount of memory it is being given, hoping the
application won't really try to use it all)

The best approach to evaluating memory usage is if you can ask the
allocator for information on memory usage directly, as that matches
the world from the point of view of the application.

leftover gradients/markers/patterns
will get automatically cleaned up when the objects that use them are
deleted.

Caveats:

* this only applies to such objects created with a build of Inkscape which post-dates this commit (June 7 2004) 

* not all automatically-created objects will necessarily be collected; the code that creates them needs to be updated to set the correct collection policy

* paint objects won't get collected until another editing operation takes place, since NRArenaShape currently holds onto an SPStyle for too long

Technical details:

Assuming its collection policy permits it, an object will be collected
if neither it nor its descendants have any outstanding inter-document
URI references (nonzero SPObject::hrefcount).

There are two "policies" for collecting orphans:

* "with-parent" - the object will only be collected if one of its ancestors is collected

* "always" - the object is always collected if unused

(a third policy might be "never", which would necessarily also prevent
that object's ancestors from ever being collected; I do not plan on
implementing it)

The policy in effect is determined by the inkscape:collect attribute.

Be careful with the "always" policy; it really only makes sense for
"private" objects that are indirectly created behind the scenes (e.g. by
selecting a fill or marker option in the GUI).

SPDocument manages a queue of objects to collect; SPObject handles the machinery for actually queueing them when their hrefcount falls (based on policy), and performing the actual collection (delete).
SPDocument::collectObjects() performs a collection pass; it's currently only called from sp_document_maybe_done().

== Inkscape Experimental SVN ==

The 'experimental' module in Inkscape SVN is provided as a kind of "scratchpad" for
working up new ideas that aren't quite ready for folding into the main codebase.
This includes architectural sketches, examples, experimental patchsets, tools & utilities, or
whatever else strikes the developer's fancy.

Please create a subdirectory within experimental/ for your work. You're welcome to either post
the stuff at the top level or create a subdirectory for yourself. Things linked in at the top level
should be considered fair game for other developers to collaborate on; items posted under
a developer's username should be considered ask-first. Same sort of idea as wiki.

One of the principles behind this module is the idea of a shared working space. Other developers
working in experimental can fairly easily see what others are working on in the tree, and perhaps
borrow or contribute ideas back and forth. Since it is by definition not 'production' code, the
work may be incomplete or in a non-compileable state, and thats O-K.

When an experiment has matured to the point of being actually useful, please move it out of
the experimental module to someplace more appropriate. Or alternatively if the experimental
work has become obsolete or irrelevant, please remove it so we can avoid having the
experimental tree get too bulky.

== Directory Organization ==

=== Distribution / Packaging Files ===

Files related to generation of distribution packages should go under inkscape/packaging, as follows:

inkscape/packaging/
common/
debian/
fedora/
fink/
mandrake/
suse/

=== "Share" Collateral ===

A variety of items are installed in addition to the program itself, and placed into a 'share' directory structured as follows:

AUTHORS
NEWS
clipart/
examples/
extensions/
fonts/
gradients/
icons/
keyboards/
markers/
palettes/
patterns/
screens/
about.svg
templates/
tutorials/

In the SVN codebase, all of these are placed in inkscape/share/ (except AUTHORS and NEWS which will be copied to share during installation. The idea is that in theory, this entire tree structure can be copied into place on the user's machine.

However, we need to provide the user some level of control over the installation. They may wish to exclude some items, or may wish to augment the default install with some items external to the Inkscape package. For example, they may wish to incorporate external clipart collections. One approach would be to install symlinks in the given component directory to the external collection. For example, if the flags package were to install into /usr/share/flags-svg/, we'd just symlink there.

=== Code modules ===
Several parts of the code were written in a modular way, and they have been
accordingly placed in subdirectories of src/, while the main src directory
still contains the biggest part. To get a first overview of the modules, you
might want to have a look at these dependency graphs before you read deeper
into the source code (outside at the moment):

[http://www.ark.in-berlin.de/gri-debug.svgz]
[http://www.ark.in-berlin.de/gri-dialogs.svgz]
[http://www.ark.in-berlin.de/gri-display.svgz]
[http://www.ark.in-berlin.de/gri-io.svgz]
[http://www.ark.in-berlin.de/gri-libcroco.svgz]
[http://www.ark.in-berlin.de/gri-libnr.svgz]
[http://www.ark.in-berlin.de/gri-libnrtype.svgz]
[http://www.ark.in-berlin.de/gri-livarot.svgz]
[http://www.ark.in-berlin.de/gri-widgets.svgz]
[http://www.ark.in-berlin.de/gri-xml.svgz]

These are not all modules! For questions about how to generate these graphs
with graph-includes, please [mailto:rwst@users.sf.net].

Question on .svgz files: Is the server sending the right 'Content-Encoding:' header?
This matters to Mozilla browsers in standards compliance mode! http://jwatt.org/svg/authoring/#server-configuration

= See Also =
* [[DirectoryReorgProposal]]
* [[InkscapeJanitors]]
* [[CompilingInkscape]]

= Links =
[http://advogato.org/article/51.html Software Quality]

[[Category:Developer Documentation]]