gala/HACKING

====== Gala Contribute ======

====== Testing the latest build ======

Get daily builds on Launchpad for Ubuntu 12.04 and later.

    https://launchpad.net/~elementary-os/+archive/daily

====== Join IRC chat rooms ======

Join #elementary-dev on Freenode (irc.freenode.net).

====== Contribute without touching code ======

Go through problem reports and check unconfirmed bugs or those lacking
information and mark any duplicates you spot.

    http://bugs.launchpad.net/gala

Help getting Pantheon Terminal translated in your language!

    https://translations.launchpad.net/gala

Answer questions.

    https://answers.launchpad.net/gala

====== Check out the sources ======

    bzr branch lp:gala

The development trunk (master, tip) is the latest iteration of the next
release. Browse it online and look for other branches at:

    http://code.launchpad.net/gala

====== Build the code ======

Prepare the source and compile:
    mkdir build
    cd build/
    cmake .. -DCMAKE_INSTALL_PREFIX=/usr
    make

Run Pantheon Terminal:
    ./gala --replace # from build/

===== Debugging Code ======

Debugging a window manager is not as easy as debugging any window application.
When the window manager processes crashes, it is stopped by gdb, so all your 
windows will get stuck. Instead, run gdb from a different tty by pressing 
Ctrl+Alt+F6 for example and executing

    gdb gala
    # once inside gdb
    run -d :0 --replace

Now, you can switch back to your X session, which will probably be on tty7,
which would be Ctrl+Alt+F7. You can then get program to crash as you usually
would and switch back to tty6 as above and you have full access to all gdb
features like "bt" for getting a backtrace. See the end of the 
"If something goes wrong" section if you have troubles starting gala a second
time from gdb.

===== If something goes wrong =====

If gala crashes, you'll usually find yourself in a pretty bad position, as you
can't give focus to a window anymore by clicking on it, so you can't enter text
either. To get things back running, switch to tty6 by pressing ctrl+alt+f6 and
execute

    gala -d :0 --replace

which will start gala on display :0, which typically is the display you'll be
running. The "--replace" is most probably not required when gala crashed.
You might experience some weirdnesses if you you try to restart gala again from
a tty. The first launch will usually be somehow ignored. If that's the case,
just hit ctrl+c, and start it again. Now it should be running just fine.

===== Gala is a mutter plugin? =====

Mutter works with plugins, although they are not implemented in the way you 
would maybe expect. In fact, you should better only load a single plugin at a
time. This plugin will then be queried by mutter for animating windows or 
workspaces and defining a few other things. The plugin also has the oppurtinity
to add arbitrary ClutterActors to the stage or registring handlers for shortcuts.

===== Adding a new shell component ====

Shell components are typically placed in the src/Widgets/ folder. They usually derive
from ClutterActor, so they can be added to the stage the wm runs in directly. Once
you defined your actor, you can go to src/Plugins.vala and add a new instance of it
to the stage in the Plugin's start() method. You can register shortcuts for invoking
your view in that function as well. To get input events on your actor, you'll have to 
call plugin.begin_modal(), which puts the stage in a mode where only the custom actors
receive events and the windows are unaccessible. When your view is closed, call 
plugin.end_modal() to make the windows accessible again. A last option to have elements
like a panel receive clicks, even when not being in modal mode, is to have a look at the
Utils.set_input_region() method. Currently, you'll have to hack your area into it 
manually, it is planned to have automatic areas for actors that request it as well later
on as we need it.

====== Important: Keep fixes for different bugs in different branches ======

Branches that contain patches to fix more than one bug will be rejected, and
you will be asked to supply a separate branch for every bug fix. However,
this doesn't apply to patches that are indivisible by nature, and that
fix multiple bugs.

The reasons to work in this way are the following:

If one of the bugs targeted by your branch is correctly fixed, but one of the
other bugs is incorrectly fixed or needs corrections, the branch won't be
accepted until everything looks ok for all bugs. This causes an unnecessary
delay for the bugs that where fixed correctly.

Suppose your branch was accepted for merging in the main one. Later, it is 
discovered that your branch introduces faulty behavior. The standard course of
action for these situations is to revert the merge that introduced that faulty
behavior. This will cause that all of your fixes are reverted (even the ones
that didn't cause problems) because there was no way of discriminating between
them. If a separate branch for each bug fixed existed, only the offending one
would have been reverted, and not all of them.

Be sure to understand this, and avoid a headache later!

====== Coding style ======

Gala's source code in general follows the K&R "One True Brace Style" (1TBS),
with a caveat: spaces are inserted before opening parenthesis.

For indenting the source code only tabs are used!
Tabs should be 4 spaces wide for code to look good.

Consider the following snippet as an example:

    int test_check ()
    {
        if (x < 0) {
            message ("Negative");
            negative (x);
        } else {
            message ("Non-negative");
            nonnegative (x);
        }
        
        return 0;
    }

Of course the best example is the current source code itself.

You can also have a look at this doc for some parts:

   http://elementaryos.org/docs/code/code-style

Keep in mind that neither the indentation rules or curly
bracket positions mentioned there apply for Gala.

====== Committing code ======

Make a branch which will contain your changes for fixing bug 123456:

    bzr branch lp:gala fix-123456

Tell Bazaar your name if you haven't yet:

    bzr whoami "Real Name <email@address>"

See what you did so far:

    bzr diff
    bzr diff | less

Get an overview of changed and new files:

    bzr status

Add new files, move/ rename or delete:

    bzr add FILENAME
    bzr mv OLDFILENAME NEWFILENAME
    bzr rm FILENAME

Note: 'bzr add' should be used only when new source or data files are added
to Gala's source directory.

After making your changes, you need to commit your work as a new revision.

    bzr commit

Bazaar will open the default text editor (in most systems, nano) where you
will write the commit message, save the document, and close it. Bazaar will
use the commit message as commentary for the new revision, so it should be
a concise summary of what you did.

To change Bazaar's text editor, add the following line to Bazaar's
configuration file (usually located at ~/.bazaar/bazaar.conf):

    editor = your_text_editor_here
    
For example:

    editor = gedit

Commit your changes in small increments. It is better to keep different
changes in different commits.

If a commit fixes a reported bug in Launchpad, it is useful to make a
reference to that bug report when committing:

    bzr commit --fixes lp:123456

Did you make changes to more than one file, but don't want to commit the
changes of all of them? You can specify which files you want to commit:

    bzr commit file1 file2

To see the last 5 revisions in the current branch:

    bzr log -l5
    bzr log -l5 -p | less

In the case you committed something wrong or want to ammend it:

    bzr uncommit

If you want to revert all the changes made after the last revision:

    bzr revert

Remember to keep your branch updated:

    bzr pull

As a general rule of thumb, 'bzr help COMMAND' gives you an explanation of any
command and 'bzr help commands' lists all available commands.

====== Push proposed changes ======

If you haven't yet, https://launchpad.net/~/+editsshkeys check that Launchpad
has your SSH key - you can create an SSH key with Passwords and Keys aka
Seahorse or 'ssh-keygen -t rsa' - and use 'bzr launchpad-login' to make
youself known to bzr locally.

If you checked out trunk, and commited your patch(es), just push it under your
username in Launchpad and you can propose it for merging into trunk. This will
automatically request a review from other developers who can then comment on
it and provide feedback.

    bzr push lp:~USERNAME/gala/fix-123456
    bzr lp-open

The last command will open a summary of the current branch in your web
browser. There, you will be able to propose it for merging into trunk.
Your branch will be reviewed by another developer. At this stage, you may be
notified that changes need to be made to your branch, so keep an eye on your
email inbox!
After the branch is approved by the reviewer, it will get merged into the main
project's source code.


What happens to all the branches?

Leave the branches alone, approved branches are cleared automatically by
Launchpad.

For larger feature branches, use the team in Launchpad to allow other
developers to work on the code with you.

What if I want to help out on an existing merge request that I can't push to?

    bzr branch lp:~OTHERPERSON/gala/fix-123456
    cd fix-123456
    # make commits
    bzr push lp:~USERNAME/gala/fix-123456
    bzr lp-open

And in the Launchpad web overview of your branch, propose your branch for
merging into lp:~OTHERPERSON/gala/fix-123456

Updating a branch that may be out of sync with trunk:

    bzr pull
    bzr: ERROR: These branches have diverged
    bzr merge lp:gala
    # Hand-edit conflicting changes
    bzr resolve FILENAME
    # If any conflicts remain continue fixing
    bzr commit -m 'Merge changes from lp:gala'

Save a little bandwidth, branch from an existing local copy that you keep
around:

    bzr branch lp:gala gala
    bzr branch gala/ gala-fix-123456
    cd gala-fix-123456
    bzr pull lp:gala

====== License ======

This document and the Gala project are licensed under the
GPL Version 3.