Older blog entries for henrique (starting at number 10)

So, you find cocos2d and think "man, I need to try it out!". Cool, so you went to your editor, open an usual "foo.py" and start typing some example...

import cocos
class HelloWorld(cocos.layer.Layer):
    def __init__(self):
...

followed by python foo.py; after some 2 minutes you got the result on the screen, but why is it too slow to start? The culprit is pyglet.

When cocos is imported, pyglet is imported as well. cocos will then try to append some resource directories to it and then the problem begins... pyglet will start indexing every file in the tree starting at ".", so if you are running this script at your home directory or inside a directory with a lot of files and directory (like a ~/dev directory as it is my case), it will add each file found in a dictionary.

The solution: Create a directory to put your code and run it there or wait for my bug report at code.google (out of time right now, but I will do it soon and let you know).

By the way, the homework is: what will happen if your game is at /usr/bin/my-ubergame and you start it in your home directory with, lets say, 15gb of mp3 and movies?

Just a quick tip. I was wondering why this error happens, but until I got the time to investigate it I just commented out the column on the model and moved on, but now (after a 5 minutes search at the django's code) I found the reason and I want to share it. The complete error message is:

Exception Type:	SuspiciousOperation
Exception Value:	
Attempted access to '/Users/henrique/tmp/uploads/half_logo.png' denied.

Suppose the project directory (where manage.py and its friends are) is: /Users/henrique/dev/someproject/. The problem is quite simple: since the directory specified for the parameter upload_to is /Users/henrique/tmp/uploads and it has a "base path" different of the place where the project is (/Users/henrique/dev/someproject/), django forbides access to it. It has a bit of reason to be, since django is avoiding you from future headaches (pollutioning directories outside your sandbox, for instance).

Of course, to fix it you just need to change the upload_to parameter to something like /Users/henrique/dev/someproject/uploads, that is inside the project's sandbox.

Today, I found this nice blog post about testing on django:

http://ericholscher.com/blog/2008/jul/26/testmaker-002-even- easier-automated-testing-django/

It is interesting to see the way the test process is realized, it makes me remember a similar problem we had on the stoqdrivers (part of the Stoq project).

In that project we needed to (automatically) test our code against a couple of fiscal printers... teorically we would need to have connected all the printers at the same computer to run the test suite, and even this being possible, the tests would run very slowly and a lot of paper would be needed (apart the risk of putting the printer in a inconsistent state, what would make the printer unusable for a day at least :)

The solution was to log all the commands sent to the printer and the output returned. Once this log was saved, we could use it to feed the code, through a virtual printer (or actually through several virtual printers, created on demand based on the list of printers supported).

I think this way of testing has a defined name, but it still unknown for me... However, it is nice to see this "pattern" being validated in other areas like web and desktop applications development.

By the way, you can check the stoqdrivers test implementation at the: project's source web browser.

Last week I went to this amazing event in Rio de Janeiro. Well, I had the opportunity to know many guys that I never met before and to know other interesting guys as well (most of them users of django, community #django- br on freenode and the mailing list at google groups).

In this event I'd participated of a coding dojo season, since I never had participated of a season before and I would like to know what is that about. That was cool... nothing like a programming contest or a project sprint, like I was thinking of it. The dojo itself is more like a trainning, where a problem is presented to a group of people and then solved using a baby steps approach together with pair programming (from extreme programming) and TDD (test driven development).

Once a pair start presenting a solution and then coding it, they have 7 minutes to move it on. A refactory can be done (since all the tests still passing after that) or then continue implementing the last solution proposed (test first, as TDD dictates). After 7 minutes, the pair is changed.

The main feature of this dojo I liked most is the fact that nobody (except the pair writing the code) can to communicate, they have to wait for the test implementation finishes and executes (passing or failing) to speak something. This leads the public to think carefully about the code/solution that is being write, what is hard if everybody could speak at same time, proposing new solutions or starting complaining about the current solution (your solution could be accepted, but you need to present the advantages or then go ahead and implement it there).

For more information: http://www.codingdojo.org/

(nothing here)

Lets say you work on a company which has an employee working at home 'cause currently he is not at company's city (and will note be for the next 2 months). That's all fine, but it got complicated to ask the "sysadmin" to give him access to our server, his response takes so long and even this way the response propably will be a "no-no, sorry".

Well, at least some things got available to our employee and he can do its work.

It is raining and it is cold in the city and another employee would like to work at home; asking the sysadmin for access is not an option, so this employee explains the other employee that there is an option if he agrees to give access to your machine through SSH, so he could try some port forwarding through SSH and access the servers freely.

The slack employee then runs the following command on your machine:

ssh -L 8888:XXX.XXX.XXX.XXX:YYY slackuser@ofirst_employee_host -N

Where XXX.XXX.XXX.XXX is the IP address of the company's server you want to access, the "8888" is the port number at your machine which you access the company's services (you access the services through localhost:8888 and it will be forwarded to "XXX.XXX.XXX.XXX:YYY") and YYY, obviously, is the port. With that, you can access the services at company normally (actually, it should be a pretty slow, but it is better than rain and cold).

(For reference and pictures, please visit this site)

All the story was just to put that tip in a context, the slack employee will be at the office in the next monday :)

So long!

Currently it is being hard to find a good job. About one month ago I went to a new company to work with smart people and interesting projects, but life is strange and no much time was required to make me think about the future and if I really had make the right choice...

There are some things that I consider essential to classify a good job. First, the most important, is how interesting is the project to develop... that is very important, even if the needed tools are not the ones you use every day and "want to use forever". Currently, there are tools for everything (or almost everything) you need to do, so you can just "join the points" and start appreciating the system to work, i.e, your own design.

Second, and this may sounds strange, is the language (or tool) used to develop. If the project is not very good, there is a chance that you enjoy the development, since you are improving your knowledge on the language that you like to write (or being in contact with new tools you didn't known before)...

If neither the project nor the tool are good, well.. you can talk to colleagues and see what they think about the projects and if there is some possibility to change the way things are done; if it doesn't work, something is wrong and it can be you!

...or it can be the company, in both cases it is worth to try finding a new job. That is exactly what I'm going to do now and I think this time things will be better; the project is good and the language is "perfect", but the people are not that good... (should I write about this combination later?)

Well, finally we have found a way to get the accounts for a contact on maemo. We need this to be able to identify the contact which the user has called through "Internet Call".

As you may have read in the post about "watching for calls through telepathy", you can have noted that all the contact information available was just an URI, kind of "sip:1234@192.168.1.55". However, this info is only enough to supply a way to search for contacts which has this URI as account "specification".

So the question over this week was: How maemo store the accounts available for a contact?. Basically, how do you can get the list of accounts by which you can make a conversation with the contact?

We've looked at the APIs available (ebook, abook, mission-control, ...) and nothing seemed to supply the list... so I went to the database file and the first attempt was to try open it and investigate tables structure or something similar that could give me some information. No way there, the db is a Berkeley DB and there is no python modules to manage this kind of database (python for maemo seems to have removed this standard module of the distribution) and I wasn't disposed to try it in C (to work with a "mysterious" DB in C was not the kind of fun that I would like to play at the moment, at least with python this could be a bit easier).

Then I had the idea to try get the VCARD info for a contact and... WELL, the information was there. One thing that I forgot to say is that through the APIs I could get each information (named "fields" there) for the contact (first name, last name, email and so forth), but the accounts wasn't available through "fields", since you can have an variable number of accounts and the function to get a contact field expects a well defined constant (note, the "vcard" is a "well defined constant").

Through the vcard, you get things like:

X-SIP;X-OSSO-BOUND:your-account-on-device@host:the-contact-account@host

The "X-SIP" value is the user account which the contact account is mapped to. For example: I've two accounts on the device: gtalk and SIP. I've the contact X which I can talk through gtalk, the contact Y I can talk through gtalk and SIP... so you need a way to say what is the user account the contact account is bounded to (in the example, for the contact Y you could ask if his account is a "gtalk" or "sip" account), it servers as an "account type" identifier.

Given this, you can now map your "sip uri" available through the "calls watcher" to a real contact on the system. If you can do this, you can get all the other contact info, like the general ones available on most of the softwares (like name, email, web address, phone and another ways to contact the same person :)

Also note that there is a python package for vcard management, it is named vobject and is available on the project page and Python Package Index (Pypi).

Hope this information can help some people having to do this kind of interaction with maemo's rtcomm.

I want something good to die for
To make it beautiful to live
I want a new mistake
Loose is more than hesitate
You believe it in your head

I can go with the flow
Don't say it doesn't matter anymore
I can go with the flow
You believe it in your head?

     - Go with the flow, Queens of the Stone Age

Telepathy rocks, and it rocks a lot! First, let me explain our problem: we need a way to watch outgoing voip calls on maemo and since maemo is, fortunately, using telepathy for its communication software subsystem (named rtcomm), we finish having to use telepathy to do this job.

In the begining, things were obscure, we didn't know the way to follow, but the folks on the telepathy IRC channel (#telepathy @ irc.freenode.net) were very cool... and so, we got the problem fixed before the expected, this motivated to write about the solution here.

The first step was to watch for new connections made to a connection manager, it is quite simple, we just need to connect a callback to the "NewConnection" event, the initial block of code follows:

import dbus
bus = dbus.SessionBus()

cm = bus.get_object(
    "org.freedesktop.Telepathy.ConnectionManager.sofiasip",
    "/org/freedesktop/Telepathy/ConnectionManager/sofiasip")
iface = dbus.Interface(cm,
    "org.freedesktop.Telepathy.ConnectionManager.sofiasip")
iface.connect_to_signal("NewConnection", on_new_connection)

When a connection is created, we need to watch for new channels being created (which can be read as "a communication channel with some of the contacts was created"), this way:

def on_new_connection(bus_name, object_path, protocol):
    conn = bus.get_object(bus_name, object_path)
    iface = dbus.Interface(conn,
        "org.freedesktop.Telepathy.Connection")
    iface.connect_to_signal("NewChannel", on_new_channel)

So when a channel is created, you got the channel type, if it is a text conversation, the channel_type parameter would be something like "org.freedesktop.Telepathy.Channel.Type.Text". For our case, we need to filter "streamed-media" conversation, so channel_type must be "org.freedesktop.Telepathy.Channel.Type.StreamedMedia". If it is satisfied, we need then attach a new callback for the "StreamAdded" event -- this callback will be fired when a voice or video data transfer has began.

def on_new_channel(object_path, channel_type, handle_type,
                   handle, supress_handler):
    if channel_type.split(".")[-1] == "StreamedMedia":
        channel = bus.get_object(conn.bus_name, object_path)
        iface = dbus.Interface(channel, channel_type)
        iface.connect_to_signal("StreamAdded",
                                on_stream_added)

Finally, on on_stream_added callback, we filter out voice channels, and get the person the user is trying to speak with:

def on_stream_added(stream_id, contact_handle, stream_type):
    # discard video channels
    if stream_type == 1:
        return
    iface = dbus.Interface(conn,
        "org.freedesktop.Telepathy.Connection")
    contact_data = iface.InspectHandles(1, [contact_handle])
    uri = filter(lambda d: d.startswith("sip"),
                 contact_data[0].split(";"))[0]
    print "new call: %s" % uri

Shazam! It works! There is two things to note, though. If you just copy-and-paste the code, it'll not work -- as you can have noticed, some callbacks needs the connection object... you have two choices here: to use lambdas to proxy the real handler passing the connection object among all the handlers until on_stream_added or you can encapsulate all these handlers in a class and define the connection object as an attribute of it, it is up to you.

The other thing is that it can seem not too simple as watch_for_voip_connections(), but you must to note that telepathy doesn't have something specific to do what we needed here, but even in this case the framework seems to be so well designed that it gives to you the power needed to do your work.

I loved telepathy since the moment I start working with it, and I expect to contribute with the project as soon as possible. Hope you like it too :)