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Little garden project

17 de Junho de 2014, por Desconhecido - 0sem comentários ainda

After three years living in Montréal we're still amazed by the fact that here we have er... seasons!!

I believe that things have a special beauty when they don't last the time we want them to last, and seasons are all about it! (some people will exclude winter here) Anyways, taking pictures may give them more lifetime without compromising too much their beauty. And sharing them here and there is somewhat sharing our happiness, which might be a good balance in the end :)

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At the time we moved the garden was just a single white thing...

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then we realized that it provided some chairs, a table and a compost container, yay!

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But the grey ground was something to be fixed...

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so we hacked it and got some land :)

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Few months later and it's finally becoming chard, beets, carrots, spinach, berries, cheries, okra, tomatoes, basil, potatoes, sage, agastache and a saskatoon berry tree!



An introduction to the Debian Continuous Integration project

1 de Junho de 2014, por Desconhecido - 0sem comentários ainda

Debian is a big system. At the time of writing, looking at my local package list caches tells me that the unstable suite contains 21306 source packages, and 42867 binary packages on amd64. Between these 42867 binary packages, there is an unthinkable number of inter-package dependencies. For example the dependency graph of the ruby packages contains other 20-something packages.

A new version of any of these packages can potentially break some functionality in the ruby package.

And that dependency graph is very small. Looking at the dependency graph for, say, the rails package will make your eyes bleed. I tried it here, and GraphViz needed a PNG image with 7653×10003 pixels to draw it. It ain’t pretty. Installing rails on a clean Debian system will pull in another 109 packages as part of the dependency chain. Again, as new versions of those packages are uploaded the archive, there is a probability that a backwards-incompatible change, or even a bug fix which was being worked around, might make some funcionality in rails stop working. Even if that probability is low for each package in the dependency chain, with enough packages the probability of any of them causing problems for rails is quite high.

And still the rails dependency chain is not that big. libreoffice will pull in another 264 packages. gnome will pull in 1311 dependencies, and kde-full 1320 (!).

With a system this big, problems will arrive, and that’s a fact of life. As developers, what we can do is try to spot these problems as early as possible, and fixing them in time to make a solid release with the high quality Debian is known for.

While automated testing is not the proverbial Silver Bullet of Software Engineering, it is an effective way of finding regressions.

Back in 2006, Ian Jackson started the development of autopkgtest as a tool to test Debian packages in their installed form (as opposed to testing packages using their source tree).

In 2011, the autopkgtest test suite format was proposed as a standard for the Debian project, in what we now know as the DEP-8 specification.

Since then, some maintainers such as myself started experimenting with DEP-8 tests in their packages. There was an expectation in the air that someday, someone would run those tests for the entire archive, and that would be a precious source of QA information.

Durign the holiday break last year, I decided to give it a shot. I initially called the codebase dep8. Later I renamed it to debci, since it could potentially also run other other types of test suites in the future. Since early January, ci.debian.net run an instance of debci for the Debian Project.

The Debian continuous Integration will trigger tests at most 4 times a day, 3 hours after each dinstall run. It will update a local APT cache and look for packages that declare a DEP-8 test suite. Each package with a test suite will then have its test suite executed if there was any change in its dependency chain since the last test run. Existing test results are published at ci.debian.net every hour, and at the end of each batch a “global status” is updated.

Maintainers can subscribe to a per package Atom feed to keep up with their package test results. People interested in the overall status can subscribe to a global Atom feed of events.

Since the introduction of Debian CI in mid-January 2014, we have seen an amazing increase in the number of packages with test suites. We had little less than 200 packages with test suites back then, against around 350 now (early June 2014). The ratio of packages passing passing their test suite has also improved a lot, going from less than 50% to more than 75%.

There is documentation available, including a FAQ for package maintainers with further information about how the system works, how to declare test suites in their packages and how to reproduce test runs locally. Also available is development information about debci itself, to those inclined to help improve the system.

This is just the beginning. debci is under a good rate of development, and you can expect to see a constant flux of improvements. In special, I would like to mention a few people who are giving amazing contributions to the project:

  • Martin Pitt has been working on improving debci to support parallel and distributed workers. Being the current autopkgtest maintainer, Martin also already got some bug fixes and fixes into autopkgtest motivated by debci use cases.
  • Brandon Fairchild is a GSOC student working on improving the debci web interface to provide more useful information, display information for multiple suites and architectures, plus making the UI work even without Javascript enabled.
  • Lucas Kanashiro is another GSOC student, who is working on investigating patterns among packages that fail their test suites, so that we can figure out how we can fix them, or if there are classes of failures that are actually caused by problems in the debci infrastructure.


On losing contacts with old friends

30 de Maio de 2014, por Desconhecido - 0sem comentários ainda

In 2010 I decided to stop using my google account. In 2011 I decided to leave facebook, twitter and other $cool stuff. This was a hard decision. Not because email migration was annoying, nor because I liked to do social networking. It's hard because most of friends depend on either google or facebook to chat. Since I moved to another country, phone calls and presencial meetings have been substantially reduced.

So we keep in contact by using IRC and XMPP. I have good friends who use IRC, mostly Debian people, which is great. I also have lots of friends and contacts not using IRC. In the past they used ICQ, then moved to MSN and now they are using google talk and facebook. I used to explain them that we could talk by using their google account and my Jabber account due to an open standard called XMPP. I enjoy having short conversations in random times, which sometimes takes hours and helps us to keep affectionately connected.

It used to work so well. Now it seems to be gone. I've noticed that I can't connect anymore with contacts using google talk, probably because google has finally put into action their decision to abandon open standards for instant messaging.

I'm not going to list here all the good things that happened in my life when I stopped using all this crap services. But I have to admit that it really hurts to see my contacts disappearing day by day, feeling like my friends are being devoured by these companies, with zero critical sense. You'll say that good friends won't disappear like that if they are good friends. I agree, but the convenience of having people from one-click distance in random hours a day makes a difference, mainly when physical distance is a blocker.



Custom Layouts on Android

12 de Maio de 2014, por Desconhecido - 0sem comentários ainda

If you ever built an Android app, you have definitely used some of the built-in layouts available in the platform—RelativeLayout, LinearLayout, FrameLayout, etc. They are our bread and butter for building Android UIs.

The built-in layouts combined provide a powerful toolbox for implementing complex UIs. But there will still be cases where the design of your app will require you to implement custom layouts.

There are two main reasons to go custom. First, to make your UI more efficient—by reducing the number of views and/or making faster layout traversals. Second, when you are building UIs that are not naturally possible to implement with stock widgets.

In this post, I will demonstrate four different ways of implementing custom layouts and discuss their respective pros and cons: composite view, custom composite view, flat custom view, and async custom views.

The code samples are available in my android-layout-samples repo. This app implements the same UI with each technique discussed here and uses Picasso for image loading. The UI is a simplified version of Twitter app’s stream—no interactions, just the layouts.

Ok, let’s start with the most common type of custom layout: composite view.

Composite View

This is usually your starting point. Composite views (also known as compound views) are the easiest way of combining multiple views into a reusable UI component. They are very simple to implement:

  1. Subclass one of the built-in layouts.
  2. Inflate a merge layout in the constructor.
  3. Initialize members to point to inner views with findViewById().
  4. Add your own APIs to query and update the view state.

TweetCompositeViewcode is a composite view. It subclasses RelativeLayout, inflates tweet_composite_layout.xmlcode into it, and exposes an update() method to refresh its state in the adaptercode. Simple stuff.

Custom Composite View

TweetCompositeView will likely perform fairly well in most situations. But, for sake of argument, suppose you want to reduce the number of child views and make layout traversals a bit more efficient.

Although composite views are simple to implement, using general-purpose layouts has a cost—especially with complex containers like LinearLayout and RelativeLayout. As platform building blocks, they have to handle tons of layout combinations and might have to measure child views multiple times in a single traversal—LinearLayout‘s layout_weight being a common example.

You can greatly optimize your UI by implementing a custom logic for measuring and positioning child views that is specially tailored for your app. This is what I like to call a custom composite view.

A custom composite view is simply a composite view that overrides onMeasure() and onLayout(). So, instead of subclassing an existing container like RelativeLayout, you will be subclassing the more general ViewGroup.

TweetLayoutViewcode implements this technique. Note how it gets rid of the LinearLayout from TweetComposiveView and avoids the use of layout_weight altogethercode.

The laborious work of figuring out what MeasureSpec to use on each child view is done by the ViewGroup’s handy measureChildWithMargins() method—and getChildMeasureSpec() under the hood.

TweetLayoutView probably doesn’t handle all possible layout combinations correctly but it doesn’t have to. It is absolutely fine to optimize custom layouts for your specific needs. This allows you to write both simpler and more efficient layout code for your app.

Flat Custom View

As you can see, custom composite views are fairly simple to write using ViewGroup APIs. Most of the time, they will give you the performance your app needs.

However, you might want to go further and optimize your layouts even more on critical parts of your UI that are very dynamic e.g. ListViews, ViewPager, etc. What about merging all TweetLayoutView child views into a single custom view to rule them all? That is what flat custom views are about—see image below.

Custom Composite View (left) and Flat Custom View (right)

Custom Composite View (left) and Flat Custom View (right)

A flat custom view is a fully custom view that measures, arranges, and draws its inner elements. So you will be subclassing View instead of ViewGroup.

If you are looking for real-world examples, enable the “show layout bounds” developer option in your device and have a look at apps like Twitter, GMail, and Pocket. They all use flat custom views in their listing UIs.

The main benefit from using flat custom views is the great potential for flattening your view hierarchy, resulting in faster traversals and, potentially, a reduced memory footprint.

Flat custom views give you maximum freedom as they are literally a blank canvas. But this comes at a price: you won’t be able to use the feature-packed stock widgets such as TextView and ImageView. Yes, it is simple to draw text on a Canvas but what about ellipsizing? Yes, you can easily draw a bitmap but what about scaling modes? Same applies to touch events, accessibility, keyboard navigation, etc.

The bottom line is: with flat custom views,you will likely have to re-implement features that you would get for free from the platform. So you should only consider using them on core parts of your UI. For all other cases, just lean on the platform with composite views, custom or not.

TweetElementViewcode is a flat custom view. To make it easier to implement it, I created a little custom view framework called UIElement. You will find it in the canvascode package.

The UIElement framework provides a measure/layout API which is analogous to Android’s. It contains headless versions of TextView and ImageView with only the necessary features for this demo—see TextElementcode and ImageElementcode respectively. It also has its own inflatercode to instantiate UIElements from layout resource filescode.

Probably worth noting: the UIElement framework is in a very early development stage. Consider it a very rough sketch of something that might actually become useful in the future.

You have probably noticed how simple TweetElementView looks. This is because the real code is all in TweetElementcode—with TweetElementView just acting as a hostcode.

The layout code in TweetElement is pretty much analogous to TweetLayoutView‘s. It handles Picasso requests differentlycode because it doesn’t use ImageViews.

Async Custom View

As we all know, the Android UI framework is single-threaded. And this is for a good reason: UI toolkits are not your simplest piece of code. Making them thread-safe and asynchronous would be an unworthy herculean effort.

This single-threaded nature leads to some fundamental limitations. It means, for example, that you can’t do layout traversals off main thread at all—something that would be useful in very complex and dynamic UIs.

For example, if your app has complex items in a ListView (like most social apps do), you will probably end up skipping frames while scrolling because ListView has to measurecode and layoutcode each child view to account for their new content as they become visible. The same issue applies to GridViews, ViewPagers, and the like.

Wouldn’t it be nice if we could do a layout traversal on the child views that are not visible yet without blocking the main thread? This way, the measure() and layout() calls on child views would take no time when needed in the UI thread.

Enter async custom view, an experiment to allow layout passes to happen off main thread. This is inspired by the async node framework developed by the Paper team at Facebook.

Given that we can never ever touch the UI toolkit off main thread, we need an API that is able to measure/layout the contents of a view without being directly coupled to it. This is exactly what the UIElement framework provides us.

AsyncTweetViewcode is an async custom view. It uses a thread-safe AsyncTweetElementcode factorycode to define its contents. Off-screen AsyncTweetElement instances are created, pre-measured, and cached in memory from a background thread using a Smoothie item loadercode.

I had to compromise the async behaviour a bit because there’s no sane way of showing layout placeholders on list items with arbitrary heights i.e. you end up resizing them once the layout gets delivered asynchronously. So whenever an AsyncTweetView is about to be displayed and it doesn’t find a matching AsyncTweetElement in memory, it will force its creation in the UI threadcode.

Furthermore, both the preloading logic and the memory cache expiration would need to be a lot smarter to ensure more layout cache hits in the UI thread. For instance, using a LRU cachecode here doesn’t seem ideal.

Despite these limitations, the preliminary results from async custom views look very promising. I’ll continue the explorations in this area by refining the UIElement framework and using it in other kinds of UIs. Let’s see where it goes.

Wrapping up

When it comes to layouts, the more custom you go, the less you’ll be able to lean on the platform’s proven components. So avoid premature optimization and only go fully custom on areas that will actually affect the perceived quality and performance of your app.

This is not a black-and-white decision though. Between stock widgets and fully custom views there’s a wide spectrum of solutions—from simple composite views to the more complex async views. In practice, you’ll usually end up combining more than one of the techniques demonstrated here.



Introducing Radio Pyo: live python music!

28 de Abril de 2014, por Desconhecido - 0sem comentários ainda

Radio Pyo is now online as a beta experiment. All the compositions are made entirely with Python and Pyo. They mostly have pseudo-random music sections, so technically speaking the chances that you listen to the same song twice are very little :)

I'm contacting the composers in order to make all the sources available in a public repository.

Here's a template with some rules for those who want to submit a composition (for now it's just about sending the script to tiago at acaia.ca):

radiopyo-template.py

#!/usr/bin/env python
# encoding: utf-8
"""
Template for a RadioPyo song (version 1.0).

A RadioPyo song is a musical python script using the python-pyo
module to create the audio processing chain. You can connect to
the radio here : http://radiopyo.acaia.ca/

There is only a few rules:
    1 - It must be a one-page script.
    2 - No soundfile, only synthesis.
    3 - The script must be finite in time, with fade-in and fade-out
        to avoid clicks between pieces. Use the DURATION variable.

belangeo - 2014

"""
from pyo import *

################### USER-DEFINED VARIABLES ###################
### READY is used to manage the server behaviour depending ###
### of the context. Set this variable to True when the     ###
### music is ready for the radio. TITLE and ARTIST are the ###
### infos shown by the radio player. DURATION set the      ###
### duration of the audio file generated for the streaming.###
##############################################################
READY = False           # Set to True when ready for the radio
TITLE = "Song Title"    # The title of the music
ARTIST = "Artist Name"  # Your artist name
DURATION = 300          # The duration of the music in seconds
##################### These are optional #####################
GENRE = "Electronic"    # Kind of your music, if there is any
DATE = 2014             # Year of creation

####################### SERVER CREATION ######################
if READY:
    s = Server(duplex=0, audio="offline").boot()
    s.recordOptions(dur=DURATION, filename="radiopyo.ogg", fileformat=7)
else:
    s = Server(duplex=0).boot()


##################### PROCESSING SECTION #####################
# global volume (should be used to control the overall sound)
fade = Fader(fadein=0.001, fadeout=10, dur=DURATION).play()


###
### Insert your algorithms here...
###


#################### START THE PROCESSING ###################
s.start()
if not READY:
    s.gui(locals())

Thanks to Olivier Bélanger and Jean-Michel Dumas for all the code!